Ultimate LS1 AC Control Tutorial - HalfSpec Engineering

[halfspec]

As I step back from producing products for the RX7 community I wanted to turn over my designs and convert my projects into a more open source form. This is one of those projects.

Terms of use – I am releasing this information freely and you can do whatever you wish with it. All that I ask is that if you do post this information elsewhere, please provide a link back to this thread. As far as support goes, this thread is it. Please don’t PM me with circuit specific or troubleshooting questions. If you have questions, post here and let the very capable community here work it out. If the question can’t be answered by the community I will hop in and answer (I’m subscribed to this thread).

93-95 RX7 LS1 AC Control
This is a tutorial for constructing and installing an electrical interface system that allows your GM AC compressor to be fully controlled with the LS1 PCM and actuated with the stock FD AC button. This is only for folks running a 98-01 fbody LS1 PCM. If you have a GTO LS1, LS2, LS3, or whatever that’s not an fbody LS1, you need to visit my other tutorial for creating LSX AC Control. This is the exact design I used to create and sell ~50 of these controllers over 3 years and they performed flawlessly with zero returns.

Diagram:



This diagram should look somewhat familiar as it’s based on Pez’s work. The only difference is that my diagram shows a little bit more of the system (pressure sensor) AND it’s got a nice little bonus. The AC Signal Intercept adapter. This is a plug-and-play adapter I developed that standardizes the controller wiring but more on that later.

How it works:

This section isn’t critical to understand, but I’m going to write it out anyway because if you have problems with the controller, this section is what you’ll need to debug it.

That Damned Diode:

Probably haven’t seen that on any diagrams to date eh? WTF do you need that for? It’s called a flyback diode and it’s a type of snubber circuit. It’s actually built into the LS1 harness wiring for the compressor if you’ve actually pulled one apart. When the voltage to the Compressor clutch solenoid is removed the coil’s magnetic field collapses which creates a pulse of current flow which therefore creates a negative voltage across the solenoid coil. This short lived reverse voltage is only around in the order of miliseconds, but it can be a couple hundred volts…. Which can pop the mini relay to the left.  The flyback diode (it’s just a regular 1N4004 diode) can snub this reverse voltage because when it pops up, it forward biases the diode which sinks everything to ground therefore protecting your relay.

RX7 AC Button Signal:

This is usually the hardest part for people to grasp. I get questions a lot simply asking how to tap into the RX7’s AC button signal and what is it (12V or Gnd)? The button is overcomplicated in its stock form for such a simple operation. That’s one of the reasons for the AC Signal Intercept Adapter, as it cuts the complexity in half. With the interceptor installed, here’s how it all works:



In the diagram above the AC switch on the lower right. Notice that it's normally open. See the leg that exits out of 1G. That's the path to ground. How? You'll see it make its way to position 1 of the blower switch. When you switch the blower switch, this is how it gets ground.

Position #1 = Direct patch to ground through the switch
Position #2 = Path to ground through the diode then to through the switch
Position #3 = Path to ground through the diode then through the second resistor then through the switch
Position #4 - Path to ground through the diode then through the second and third resistors then through the switch

My theory on position 3 and 4 and the resistors is that the resistors are very low resistance (like 1-2ohms so they're negligible). The first resistor is a little more substantial therefore the diode path is there to shortcut it in position 2, 3, and 4.

*Note* A fully functioning blower resistor is key to getting a ground signal to the AC switch. If you have a break in the blower resistor’s wiring, your AC won’t function in 1 or more positions. This is important because I’ve seen this problem with customers several times over the years and it appears to be getting more and more common as our cars are getting into their mid 20s. If your AC button doesn’t actuate the mini SPST relay, my first suggestion is to inspect and verify your blower resistor is working.

When you press the AC switch and your blower switch is in position 1-4 you get a ground out of 1l. This makes its way to the thermoswitch connection G-08.

This is where my proposed adapter picks up the signal. Creating an adapter at G-08 to pickup the signal after the thermoswitch allows us to pick up that ground coming from 1l and use it to activate the Micro SPST relay. Pay special attention to how the AC Signal Intercept Adapter is wired. The violet wire does not pass through to the other side of the adapter. It gets re-routed directly to the micro relay pin 85. You have to do it this way to insure that the factory Fan #1 relay doesn’t interfere with the AC request signal.

When the ground signal from the RX7 AC switch activates the Micro SPST relay we get 12v sent to the LS1 PCM’s A/C Request Signal input. This tells the LS1 PCM that the car’s operator is requesting AC and it begins the process of turning on the compressor.

PCM Compressor Control 1:
When the LS1 PCM receives 12V on AC Request Signal input it starts the process of determining whether or not the compressor can be tuned on by analyzing the following conditions:

1.   Is the refrigerant pressure between its high and low setpoints (won’t let the compressor turn on if there is an overpressure condition or a loss of refrigerant) via the LS1 pressure sensor.
2.   If the engine’s RPM is under a high condition setpoint (won’t let the compressor come on if you’re in the middle of a redline pull)

PCM Compressor Control 2:
After the PCM is satisfied the compressor is ok turn, it sends a Ground signal out of the PCM’s A/C Clutch Relay Control output with actuates the Mini SPST relay and sends 12V to the AC compressor clutch. At the same time it monitors the mini SPST’s 12V output to the compressor clutch to make sure it’s 12V when the compressor is supposed to be on. If the PCM ever orders the compressor on and it doesn’t receive 12V on the A/C Status Signal it knows the relay is either missing or defective and you’ll get a CEL code and no AC.

PCM Fan Control:
After the PCM is satisfied the compressor is ok to turn on it also enables its radiator low speed output. This output remains on during the entire AC request process with one condition. The condition is that the LS1 PCM monitors the vehicles speed through the VSS sensor so when you’re approaching highways speeds the fan output is disabled. This makes sense if you think about it because really, radiator fans are only good for a certain CFM and at some point the car will be going fast enough that the air being forced through the condenser + radiator is greater than the CFM output of the fans so at that point you don’t need the fans and it’s better just to turn them off and let the car’s speed force air through the condenser + radiator. This elegant feature of the fan control is one very big reason to keep the PCM in control of your radiator fans and pass on aftermarket solutions.

So now that you know what this is for and how it works, let's move onto the parts list needed to build one of these 

Lane

[halfspec]

Parts List



The parts list above is fairly comprehensive. The only thing you may run into is order quantity limitations. Waytekwire is especially picky about low quantity orders which is why I tried to add as many alternatives as possible. Either way, this should give anyone a huge head start on getting one of these high quality controllers built even if the original sources dry up.

Tools of the Trade

As with everything car related, you have to have the right tools to do the job well. That is especially true when you're building something like this. A high quality stripper / crimper will make your life a lot easier, whereas the incorrectly spec'd or insufficient stripper / crimper will make your life a living hell. Believe me. This will be one of the big hurdles DIY folks will face, because we're not just talking pocket change here.

I own the following 3 crimpers:

Pressmaster KRB-0560


S & G Tool Aid 18920


Cycle Terminal ECT47


I also own the following stripper:

IDEAL 45-092 Stripmaster Wire Stripper


All 4 of the tools above have been worth their weight in gold.

The S & G Tool Aid 18920 was my first ratcheting crimper. It's a good starter crimper and does a lot of things pretty well in the medium of its range. It can handle Delphi 150-480 terminals and it has a great die for crimping barrels & butts.  It's the large and small stuff where it starts to struggle (see my comments on the next two crimpers). I believe a good alternative for this crimper is the Cycle Terminal Eclipse Crimper. The only thing I'm not sure about when it comes to the Eclipse crimper is what dies it comes with and what you have to purchase seperately. It makes it sound like it comes with the barrel / bullet die already which would mean you'd probably want the optional "Die for Open Barrel Terminals" or "Die for Small Ring and Splice Terminals " depending on what you're crimping. May be a way to save money over the S&G depending on your application.

The Cycle Terminal ECT47 crimper is for small stuff. I use it almost exclusively for crimping PCM terminals as they're generally made for 20-24AWG wiring and it's just too small for the ratcheting crimpers I have.

The Pressmaster is absolutely amazing. I bought it late in the game as I resisted paying $150+ for a crimper for years. However, after getting it I can't believe how much time and pain it saves me. This is the only crimper I own that can crimp the .312 YMST1418L / YFST1416N terminals. The S&G just doesn't have the leverage to do bigger terminals unless you're related to Hercules and/or can figure out how to use your hydraulic press to help actuate the handles. Seriously, I kiss this one every night before I go to bed.

The ideal stripmaster is one of those tools you can't believe you lived without before you got it. Seriously, it's saved me DAYS in time over the years I've owned it.

Finally, when doing work with small terminals and connection systems that use tangs / locking tabs to secure the terminals, it is VERY important that you have the proper tools to de-pin the connector you're working on. Seriously, you can do a lot of damage and waste a lot of your time trying to use a tool that isn't designed to de-pin. I suggest getting the $13 option from cycle terminal that includes a wide and narrow de-pinning tool:



Lane

[halfspec]

Build Instructions

I imagine this is the section most folks are waiting for 

Step 1 - Build the Power Harness




The specifics parts needed are:

6ft Pink 14AWG TXL/GXL wire (main length section)
2in Pink 14AWG TXL/GXL wire (fish-hook / fuse box connection section)
Three lengths of 2 1/2in Pink 18AWG TXL/GXL wire
Mini in-line fuse holder - 46025
Mini 25 A fuse - 46258
.312 Male Terminal = YMST1418L
.312 Female Terminal = YFST1416N
Two Mini relay terminals = 75280
Two Micro relay terminals = 75290



1. On the first end, solder and shrink wrap the 14AWG wire and the fuse holder.
2. On the other end of the fuse holder slice a section exposing bare wire and solder one of the 18AWG wires to it. *Note* Plan and shrinkwrap this connection.
3. At the end of the fuse holder wiring, crimp the Mini relay terminal together with a 2 1/2" Pink 18AWG wire.
4. At the end of the previous 2 1/2" Pink 18 AWG wire, crimp a micro relay terminal along with the second length of 2 1/2" Pink 18AWG wire
5. At the end of the previous 2 1/2" Pink 18 AWG wire, crimp a micro relay terminal along with the second length of 2 1/2" Pink 18AWG wire
6. Finally, at the end of the previous 2 1/2" Pink 18 AWG wire, crimp a mini relay terminal



1. On the second end of the 14AWG pink wire, crimp the .312 Male Terminal together with the 2 1/2" pink 14AWG wire.
2. On the other end of the 2 1/2" pink 14AWG wire crimp the female .312 Female Terminal

Step 2 - Build the AC Signal Intercept Adapter



The specifics parts needed are:

3ft Purple 18AWG TXL/GXL wire
3 sections of 2 1/2in gray 16WG TXL/GXL wire
Micro relay terminal -75290
Yazaki CN-A 4 pin Connector Set




1. Crimp a Yazaki CN-A male and female terminal on each of the 3 sections of 2 1/2in gray 16WG TXL/GXL wire
2. Crimp the Micro relay terminal on one of the 3ft Purple 18AWG TXL/GXL wire
3. Crimp a Yazaki CN-A female on the other end of the 3ft Purple 18AWG TXL/GXL wire
4. Assemble exactly as shown.

Step 3 - Build the Compressor Clutch harness




*Note this tutorial only shows how to build the harness tipped with a connector suitable for a LS1 fbody compressor. If you have a different compressor, you may need a different connector.

The specifics parts needed are:

8ft Black 16AWG TXL/GXL wire
8ft Dark Green 16WG TXL/GXL wire
Two AC Compressor Terminals - 829-12048074
AC Compressor Connector - 829-12162017-B
AC Compressor Connector Lock - 829-12124824-B
Two AC Compressor Connector Seals - 829-15324973
Ground Terminal Ring -31004
One Diode - 512-1N4004



1. Slide the seals on the dark green and black wires.
2. Position the diode so the legs slide through each of the seals and meet the tips of the black and green wire. Note the polarity orientation in the pic and schematic! Note 2 - Involving the the diode makes this a tricky crimping operation. I'd recommend dabbing the crimping section of each terminal with solder if possible to insure the diode is bonded to the terminals.
3. Crimp the terminals on the dark green and black wires.




1. Align and press in the terminals and seals in the compressor connector.
2. Sleeve if so desired



1. Crimp the Ground Terminal Ring on the end of the black wire.
2. Leave the dark green wire un-terminated (for now).

Step 4 - Build the Pressure Sensor Harness




The specifics parts needed are:

6ft Gray 18WG TXL/GXL wire
6ft Purple 18WG TXL/GXL wire
6ft Red/Black 18WG TXL/GXL wire
Three PCM Terminals - 829-12084912
Three Pressure Sensor Terminals - 829-12089290
Pressure Sensor Connector - 829-12065287
Pressure Sensor Seal - 829-12065285-B



1. Thread the wiring through the seal and connector as show.
2. Crimp terminals on the wire ends.



1. Pull wiring back through the connector until the terminals seat / click.
2. Re seat seal



1. Crimp PCM terminals on the other ends of the pressure sensor wiring.
2. Sleeve wiring if so desired.

Step 5 - Build PCM wiring



The specifics parts needed are:

2ft Dark Green 18WG TXL/GXL wire
Two Sections of 2ft Dark Green / White 18WG TXL/GXL wire

Three PCM Terminals - 829-12084912
Two Mini relay terminals -75280


*Note* Please make believe that the blue / white wire = Dark Green / White

1. Crimp PCM Terminals to one end of each of the three wires.
2. Crimp Mini relay terminals to the ends of each of the Dark Green / White wires (not shown). Don't crimp anything to the Dark Green Wire yet.

Step 6 - Final Assembly




The specifics parts needed are:

Mini relay terminal = 75280



1. Crimp the 2ft 18AWG dark green PCM wire AND the dark green wire of the Compressor Clutch Harness together with a Mini relay terminal
2. Assemble and label the rest of the connections referencing the pictures and diagram above.
3. Install relays
4. Have a beer or 10.

Closing Notes

1. You may notice that I sometimes say connect to pin 85 in my schematics and I connect to pin 86 in my pictures or vice versa. Polarity doesn't matter with the relays I've specified so the two are 
    interchangeable. As long as a ground is on one side and 12V is on the other side, the relay will activate. Pins 87 and 30 are also interchangeable. I just make use of this fact to simplify wiring.
2. If you want to get into the nitty gritty. I don't crimp my seals correctly in the pictures above. The secondary crimp on the terminals is supposed to be used to crimp the seal AND the wire insulation like this:

As a amateur I just crimped to the wire insulation as having the seals movable have me a little bit of flex for moving things around like the diode on the compressor connector. Still, if seals are involved and you want to do it right, try and do it like the picture above shows.

- Lane

[halfspec]

Installation

Ok so you’ve got your controller built and it looks a little something like this:




Time to install it!

This installation tutorial is divided up into 3 parts. Part 1 covers the RX7 electronics side of the install. Part 2 covers the LS1 PCM side of the install. Part 3 covers the initial power up and testing.

Part 1 – RX7 and chassis wiring



1.   This controller is made to be mounted in the passenger side kickpanel area, so that’s where it will be easiest to locate everything unless you’ve tailored your wiring and deviated from the plans above.
2.   Prepare 1 of the 3 or 4 studs in that area to be used as a ground location. This means to remove any paint down to the bare metal and any dirt away from the base of the stud.
3.   Using the 6mm lock nut included in your kit, bolt the ground terminal to this prepared stud. See the pic below:


Note – This stud has NOT been prepared properly. Please make sure the ground terminal makes good contact with bare metal at the base of the stud.

4.   Remove the 25A fuse from the 12V switched wire.
5.   After removing the fuse, route the 12V Switched plug from the passenger side to the driver’s kick panel. I find that routing along the firewall and over the transmission tunnel to be the most direct / clean route.
6.   Unplug, unbolt, and unclip the driver’s side fuse box. Tip #1 – Remove your kick panel and dead pedal. Tip #2 the fuse box has one bolt towards the floor board and one VERY hard to reach clip at the top (See pic below). Please be careful not to break this clip. It is possible to see the clip with some finagling, but it IS difficult and probably one of the more frustrating parts of the job.



7.   Flip the fuse box over and look for 3 position black connector with three large wires colored Blue, Black/White, and Black/Yellow.



8.   Unplug the black connector and use a small flat head screw driver to de-pin the Black/Yellow wire.



9.   The pin should come out looking like this:



10.   Slide some ¼” shrink up and over the female terminal above.
11.   Install the Male side of the 12V Switched Plug onto the original Female terminal above, then heat the shrink-wrap over the connection (not shown).
12.   Plug the Female side of the 12V switched Plug into the black connector like this:



13.   Push the connector into the black connector until it clicks.
14.   Reassemble your fuse box and replace any panels you removed to access it.
15.   From the passenger kick panel, plug the A/C G-08 Signal intercept adapter between the Evaporator’s Dash Wiring and its Thermoswitch:

*Note* G-08’s location has been a subject of confusion for many over the years I sold this controller. Folks can’t seem to find the thermoswitch plug G-08. It’s slightly different for Mana and Denso evaporators. Here is the diagramed location:


The thermoswitch is labeled as '4' in the pictures above and G-08 is the 4 pin electrical connector at the end of its wiring pigtail

Here’s my Denso connector hanging down from its clip (It’ll be clipped up further in the dash via its stock configuration unless someone’s been toying around (like me in this picture))



And finally, here’s a member’s Mana G-08 clipped to the evaporator case as it should be:



16.   From the passenger kick panel, route the compressor control plug to the compressor. The length instructions above are meant to route through the airbag harness grommet and up and over the inside of the fender to right in front of the wheel where it can easily make its way to the compressor. Kind of like the picture above but on the passenger side:



17.   The method above does require the temporary removal of your fender.
18.   Another method would be to route through the engine harness grommet or drill a new hole and install a new grommet to pass through.
19.   Plug in the compressor control plug.

Part 2 – PCM connectors




You labeled your wires when you build your controller riiiight? 

1.   For 98 fbody PCMs these are the installation instructions:

a.   C2 Red PCM Connector Pin #14  = ACSTATUS Wire (Dark Green)
b.   C2 Red PCM Connector Pin # 39 = CLUTCHCTRL Wire (Dark Green / White)
c.   C2 Red PCM Connector Pin # 47 = ACREQ Wire (Dark Green / White)
d.   C2 Red PCM Connector Pin # 63 = PRESSUREGND (Purple)
e.   C1 Blue PCM Connector Pin #7 = PRESSURESIG (Red / Black)
f.   C1 Blue PCM Connector Pin #66 = PRESSURE5V (Gray)

2.   For 99+ fbody PCMs these are the installation instructions:
a.   C2 Red PCM Connector Pin # 18 = ACSTATUS Wire (Dark Green)
b.   C2 Red PCM Connector Pin #43 = CLUTCHCTRL Wire (Dark Green / White)
c.   C2 Red PCM Connector Pin #17 = ACREQ Wire (Dark Green / White)
d.   C2 Red PCM Connector Pin #14 = PRESSURESIG (Red / Black)
e.   C2 Red PCM Connector Pin #57 = PRESSUREGND (Purple)**
f.   C1 Blue PCM Connector Pin #45 = PRESSURE5V (Gray)

**Note – For 99+ fbody ECU’s the pressure sensor’s ground (purple wire) Is connected to the PCM’s ground through pin #57. Unfortunately this ground is also shared by the Intake Air Temperature sensor. The solution is either to tap into the existing wire on pin 57 OR to de-pin the existing wire, plug in the new pressure sensor wire and take the IAT wire and tap into the new pressure sensor wire. Either way the end result should be that two purple wires share the connection to pin #57. The diagram explaining this setup is shown below:



Pinning / De-pinning the PCM connector is easy. Just unclip the clear colored lock/guard of the connector which identifies it as red or blue and push the new connectors through the backside:



Afterwards replace the clear colored lock/guard and reconnect it to your PCM.

3.   From the passenger kick panel, route the pressure sensor plug to the drier in the engine bay. The length instructions above are meant to route through the airbag harness grommet and up and over the inside of the fender to right in front of the wheel where it can easily make its way to the compressor. See pic of compressor control plug above.

Part 3 – Powering up and testing

1.   Plug the 25A fuse into the 12V Switched wire’s fuse holder which is near the relays in the passenger kick panel area.
2.   Turn your key to the ON position, turn on your fans, then press the A/C button. You should hear one of the relay’s click or at least feel it click if you touch it while toggling the A/C switch. If it does and your PCM wires are properly connected, you’re done!
If not, check the unit’s 25A fuse. If the fuse is intact, check your ground terminal. If needed clean the contact point again. If that fails, move the ground to another location. If it still doesn’t click when pressing the A/C switch please post your questions here and the norotors member will help you.

Otherwise, you should now be able to enjoy the full benefits of having a PCM controlled A/C system.

[halfspec]

Done



Lane

[TravAZ]

Great info in this thread.  Thanks for being so detailed.

Sorry to revive such an old thread, but I am having issues with getting an AC signal request from the AC switch to the micro relay using the adapter.  I have checked everything and it leads back to the purple wire not providing a ground.  Everything is plugged in correctly as the instruction state and it wont work.  When I manually ground the purple wire, the relay now clicks and everything works as it should. 

Why would this be the case?  Do AC buttons go bad?  Is there another place to grab the AC switch ground? 

[halfspec]

Is your fan blower working?

[TravAZ]

Yes.  Light comes on the AC button and all speeds of blower work. 

Picture of connection on where I am trying to pickup signal for reference. 

[halfspec]

It looks like you're in the right place concerning the G-08 connector which is normally what people struggle with (lots of similar plugs in the area).
Things to check:

1. Make sure the gray wires of your signal interceptor aren't crossed. I.E., it should function as a coupler / straight pass for the violet/pink, white, and blue/yellow wires.
2. Verify that the white and blue/yellow wires are shorted together. This is supposed to happen in the G-08 connector and can be seen in the wiring diagram in the first post. I believe the two white wires on the other side of the G-08 connector make this happen and can be confirmed by peeling back some of the wiring sleeve where you can see that the white wires are really just 1 wire looped. Of course, this is by memory, so it might be the green wires.

I've never seen an AC switch fail on an FD. I can't say I've ever seen a thermoswitch fail either, but if you check the above, I'd say that's what you're down to.

3. To determine if the thermoswitch is at fault, you can grab the AC switch signal at the violet/pink wire via G-08. This is the AC switch signal pre-thermoswitch. If it works on the violet/pink wire, you've simply got defective thermoswitch that's stuck open.
4. If you still can't get a ground out of the violet/pink wire, then you've got a problem with the AC switch being able to provide a ground which is most likely because it's path to ground on the other side of the switch is broken. As mentioned in #2 above, an easy way to break the AC Switch's path to ground is to not have blue/yellow and white shorted together via a G-08 mistake. Aside from that, if your blower works on position 1, that really verifies the blower switch is providing a ground to blower motor through the blower resistor which is the same path the AC switch takes, so that should be fine. I suppose you could manually ground the G-08 white wire if nothing else pans out and check the operation of the AC switch. Grounding the white wire takes the blower resistor and blower selector switch out of the equation and just gives a constant ground to the input side of the AC switch making it so the AC switch can give a ground signal out of the violet/pink wire (and later via the violet wire post-thermoswitch) independent of the blower switch's position.

Lane

[TravAZ]

Well, still no luck in understanding my issue.  Below is where I am at now...

Wires look normal and all connections look fine with the white wire being looped to provide a short as you stated. 






Check resistance at several points to see if/what grounds are working.  I can't get any ground readings before or after the thermoswitch with the ac button on.  I checked violet/pink before adapter, green coming back from thermoswitch, and purple going to relay.  All had the below same readings....

Car Off


Car in ACC/Not Running With AC Button Not Pressed and Not Illuminated 


Car in ACC/Not Running With AC Button Pressed In and Illuminated


I took off the HVAC controls and inspected the AC button and wiring.  Everything looks fine, but is too complicated for me to test.  If the button works and lights up, I think it is fine.  I am worried about the electrical after the button in the HVAC boards or somewhere else. 

My setup is running this harness through a LS1 2001 PCM.  All fan relays have been deleted and I am running an integrated Flexlite fan controller.  When I ground the purple wire to the microrelay, the system works great.  Fan kicks on, AC clutch engages, and I have really cold air thanks to the R12 charge and all new components installed. 

I am guessing I need to order a new/different HVAC control system, but I am hoping there is another option on provided the AC signal ground to the relay. 

Thanks for all of the help!

[halfspec]

Quick question that may become relevant. Was your car originally an auto or manual?

You've done a good job troubleshooting the output of the AC switch and thermoswitch as not behaving correctly and sending out the ground. There's a little bit left to check, but we'll get into that momentarily. I'm a little confused by your meter readings, but I know 194ohms is too high to be a short and I'll assume "1  ." means open. I'll also assume your other lead is connected to chassis ground since I can't track that in your pics. As long as those assumptions are ok, we can move on to troubleshooting the rest of the ac switch output.



Assuming your car is a manual, start with the Violet/Pink wire leaving position 1I of the HVAC black connector G-01 while its still plugged into the back of your HVAC panel and check to see if it shows low resistance / continuity to ground when the blower switch is in position 1 and the ac switch is pressed.


For more zoomed out pics of G-01, check out my annotated harness display here. Specifically, it's in the instrument harness

If not, move on to the next section troubleshooting the AC Switch input wiring. If you DO get your ground signal, track the wiring back to G-08 through X-17 and G-13 to see where you lose the wiring / signal.


Step 2 - Troubleshooting the input of the AC switch.

Specifically, the AC Switch's patch to ground so that it can actually send out a ground when the switch closes:



If I were you I'd want to verify that you've got a good ground all the way to the AC switch. In this instance, that's the white wire that goes to position 1G of the black HVAC connector G-01 as seen below:

With the blower switch in position number 1 you should get a low resistance / continuity to ground on the white wire going into position 1G of the black HVAC connector G-01. If not, work your way back to G-12, G-08, and finally to G-02 until you pick it up and figure out why it's not making its way all the way to G-01.


If, you get a good ground with the white wire at position 1G of connector G-01 and your still not getting a ground out of violet / pink wire leaving G-01 via position 1I when your blower switch is in position 1 and your AC switch is depressed, then that's the point where I would start asking around for a loner HVAC panel to swap in and verify that it fixes the problem.

Lane

[TravAZ]

Car is a 1993 Touring and I bought it already swapped.  It looks like a stock manual car, but how do I make sure it was?  VIN #?  Certain things on car?  Barely anything is stock...  What would be the difference in troubleshooting if it was stock auto, not manual?

You assumption on using a chassis ground was correct.  Great info/idea on checking the wiring on the back of the HVAC controls.  I will do that tonight.

[halfspec]

Not really sure about automatic identification. I'm not even sure if auto gauge cluster have gear indicators on them.
Maybe Google site:rx7club.com auto identification?
Vin decoding would probably work too.

Autos have some wiring differences. You'll see dashed boxes circling the differences in the wiring diagram. The diagram in this thread has an example. It's not ever really an issue with the AC controller wiring, but in your case, detailed wiring route tracing ma :)y differ on the output side of the AC switch.

Lane

[Cobranut]

Not really sure about automatic identification. I'm not even sure if auto gauge cluster have gear indicators on them.
Maybe Google site:rx7club.com auto identification?
Vin decoding would probably work too.

Autos have some wiring differences. You'll see dashed boxes circling the differences in the wiring diagram. The diagram in this thread has an example. It's not ever really an issue with the AC controller wiring, but in your case, detailed wiring route tracing ma :)y differ on the output side of the AC switch.

Lane

Lane,

My car was originally an auto, and it does have gear indicator lights in the cluster.
The red R even comes on with the backup lights.   

I actually like the Auto cluster, as the 7K redline matches my stroker motor well.

[TravAZ]

Well, still at it and still not finding this issue.  Below is what I did this time around...

Pulled back out the HVAC panel to access the wiring.  Tested Violet/Pink leaving G-01 while still plugged in.  No resistance with any combination of car on or off or AC on or AC off with blower position on #1.  It would appear that no matter what I do, it would NOT push out a ground. 

Checked the ground to the AC switch by checking continuity of white wire position 1G on connector G-01.  Below were the results...
Car Off - resistance reading at position 1, more at 2, more at 3, and more at 4
Car On - no resistance reading, but blower control works and will adjust from speed 1 to 4

To me, it would look like the only missing link is the AC switch or the HVAC circuit board....

I am missing anything?   I would prefer to just order the AC switch on ebay, but worry it wouldn't fix the issue because it is in the board.  The wiring all looks good inside the HVAC controls with good soldering and no burnt spots on the board.

Is there any outside the box way to just run another grounded toggle switch to send a ground directly to the mini relay?  Would this mess with the working of other systems correctly?