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Another hybrid (Ford/GM) A/C newbie idiot.....

jw33 on Sat May 16, 2009 1:15 AM User is offline

Year: 91/06
Make: Ford/GM
Model: Mustang/GTO
Engine Size: 6.0
Refrigerant Type: 134a
Ambient Temp: 95
Country of Origin: United States

I have a '91 Mustang that has a GM LS2 motor from a '06 Pontiac GTO. The car has been on the road now for a little over a year and I am of course now starting to research hooking up the air conditioning when I redo the interior this fall. What I think I'll be using so far is the Ford evaporator since it fits inside Mustang location and a GTO/C5 Corvette compressor (V7?). The rest is pretty much up for debate and I know I have more than just a few choices. I also have a 98-02 Camaro condenser laying around that I could use if it would work with my setup. My main concerns right now are what type of connectors I should use on all of the different connections throughout the system? I can remove the existing evaporator/condenser fittings and cut/braze on a new type, which to me seems like the best idea, especially if I'm going to use non OEM lines. I'm also confused about what type of controls the compressor will need to have. I understand the basics of automotive air conditioning, but some of the newer compressor systems are bound to use different A/C controls then my Mustang has in the dash. I would think I would just incorporate all the needed sensors (pressure, temp, ect.) into the a/c lines.

Matt L on Sat May 16, 2009 5:51 PM User is offline

If the GTO uses a compressor clutch, how about using the GTO's compressor and making up some custom lines, so that it's Ford from there on out.

jw33 on Sat May 16, 2009 8:56 PM User is offline

Yes I plan on using a GTO compressor since I'm running all the other GTO front accesories on the motor. I beleive it is what has been called on this site a V7 and it is basically the same a corvette/camaro/CTS-V compressor.

Chick on Sat May 16, 2009 9:10 PM User is offlineView users profile

Use the GM lines, but have them made by a hose shop to accept the Ford evap/condenser fittings (Springlock) rather than welding the evaporator and condenser fittings. this way you can keep the part of the line (high side) with the pressure transducer on it.. You are using the GTO computer, right?? That is all you need to operate the system as far as pressures go, the inside controls are easy to adapt.. Having new lines made to fit the existing fittings is the way to go, and although will cost a few bucks, it eliminates a lot of headachs.. The shop that does the hoses can make sure the accumulator and evap along with the condenser all fit properly using new fittings crimped onto barrier hose.. Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

jw33 on Sun May 17, 2009 1:09 AM User is offline

I am running an E67 PCM that is flashed with a file for a CTS-V which uses the same motor as the '05-08 C6 corvette, Trailblazer SS, '05-'06 GTO, and the SSR pickup. In other words if you were to plug in a GM TechII tool into my ODB port it would show up as a 2007 CTS-V vin. Crazy right? How exactly does the engine PCM interface with the a/c compressor what does it read/receive from the a/c system? I would assume it might control the compressor clutch in a WOT situation and maybe turn on the electric fan when the a/c is running.

jw33 on Sun May 17, 2009 11:20 AM User is offline

I've been doing a lot of reading and it looks like I may be better off finding a different style compressor that will fit in the stock location for my motor. The variable compressor gets some of it's information from the BCM (body control module) and then talks to the engine PCM via CAN network. In other words I could be getting into another electronic rabbit hole with no end in sight. This appears to be a common problem with guys wanting to use a/c with the GM LSx series motors, especially the generation IV like I have.

bohica2xo on Sun May 17, 2009 5:13 PM User is offline

Run the V7. There is no better compressor for your application.

The pressure transducer communicates with the PCM to provide load data for idle speed & activate the fans. The BCM / CanBus crap is only for the A/C request when using the BCM system. You can still have A/C without the BCM.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jw33 on Mon May 18, 2009 12:56 AM User is offline

Man, I hope you're right, but I haven't had much luck finding the in's and out's for the controls with my PCM (E67). My harness came straight from GM as a stand-alone harness for the LS2 motor into any car and it does not have any a/c provisions. I will need to add a few pins to the main PCM connectors and then buy the plugs that go to the various sensors and the compressor. Not impossible, but that information is going to be kind of hard to come by.....

byrden on Mon May 18, 2009 7:55 AM User is offline

Wiring LS1 a/c to my RX-7 wasn't hard at all. The pcm has 3 wires to the pressure sensor (it uses for low/high pressure cutout), a wire to send a signal to the compressor clutch relay, and a "monitor" to the hot wire to the clutch that it checks to make sure the clutch is powered. The only other wire is a +12v signal to the pcm for the a/c request signal. There is a wealth of information for lsx engine conversions to other cars on I'm sure answers to many of your swap related questions reside there.

The pcm looks for enough pressure to turn the system on, will shut the system off when the pressure is too high. It will turn it off with over something like 4000rpms, and/or throttle over 80 some percent. It will also turn off the a/c when the engine coolant temperature gets too high. It will turn on/off the low speed fans with a/c request and will turn them off when you reach like 30 mph.

The v7 is supposed to be a very good compressor. Worst case keep the compressor and just control it with the car's controls, all it needs is +12 volts and a ground to turn on. The motor is big enough, it could probably care less about extra load at idle without having to anticipate the load from the pcm. If you go that route make sure to incorporate a high pressure cutout if you plan to use r134a.

bohica2xo on Mon May 18, 2009 10:41 AM User is offline


The approach you use to run the compressor depends on two things:

1) How much of that Goat you used building the car. If you kept the stock electric fans, you need the PCM control. If you installed the mechanical fan from an H2, you do not...

2) Do you prefer the brute force approach, or the OEM style?

Since you have the crippled wiring harness, you will need to add a few pins to the PCM connector if you plan to use it to control the compressor. The wiring diagram is no big deal really.

Do you have any pics of the install?


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

jw33 on Tue May 19, 2009 12:12 AM User is offline

Yeah it would be nice to have all those features and I don't think it will be that hard after all. I'd prefer to do this OEM style for looks and function. I imagine the only thing in the a/c as far as hardware is concerned that will be ford will be the evap and possibly the receiver/dryer. My car is exactly the same as a GTO under the hood except I have different headers, air intake, and I'm running the stand alone GM harness. It uses an E67 PCM instead of the GTO E40. The E67 is more widely used among other GM vehicles (TBSS, CTS-V) and the E40 is considered an oddball that's used by the GTO only. I'm running all the GTO accessories (alternator, water pump, power steering) except of course the a/c compressor and I do have the stock bracket and tensioner assembly. It locates the compressor on the lower passenger side of the motor and it has it's own 3-4 rib belt/tensioner. I'm using a stock 98-02 Camaro radiator with the stock dual electric fans. I am controlling both fans together through the PCM though so that they are either both on or both off. I need to dig around on LS1tech and try to find a E67 pinout so I can figure out what wires/pins I'll need to add to the main harness. On to the pictures....

bohica2xo on Tue May 19, 2009 3:07 PM User is offline

Man that is one confused ford. Nice job, I can just hear the mushbang kids crying... LOL

The (a/c) plumbing is not too bad, but it looks like you will need to use a TXV & receiver/dryer - I don't see any room for the OEM accumulator. Not that that is a bad thing at all, I prefer a TXV system & have added them to more than one ford...

The pressure sensor needs to be in the high side line. There is some confusion with the fans. The Goat used two fans, while the CTS-V used 3. Both vehicles have a multi speed protocol to minimize electrical loads. How are you running the fans right now?

I can e-mail you some pin-outs & diagrams if you want them.

"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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