Those who know air conditioning, please look inside

[dville_gt]

So I am trying to adapt AC to my ls1 powered coupe. I think I have acquired all the parts. To try to simplify the install I decided to cut apar the Ford Heater box and fit the ls1 evaporater inside of it (I had to cut the bottom off of the heater box and fiberglass a new bottom since the ls1 evaporator is a totally different size than the fox.

Anyways, I want to make sure that the setup will work as I have it before I try to get custom lines made. I am using a truck compressor/manifold and the rest of the parts are from an ls1 fbody (condenser/evaporator/accumulator). One thing that seems strange is that the ls1 has a pressure switch on the line that leaves the evaporator going to the condenser and the trucks have a pressure switch on the line leaving the compressor going to the accumulator. I figure since I am using a PCM from a truck I should go ahead and use the pressure switch that is between the compressor to the accumulator, but wouldn't one of these pressure switched be on the high side and the other on the low? Seems strange since GM typically does things the same between all the ls cars.

Also, where is the orfice or expansion tube. Is it in the line leaving the evaporator? The pipe does get kinda fat there so I guess it could be in there.

Here is a picture of the system as of now, see anything that doesn't make sense? Any missing parts?

[HOOCBB]

The orifice is always located before the evaporator, otherwise the pressure in the evaporator would be high and you would not have cold air from the vents.

Take a look at the line that wraps around the bottom of the evaporator. The orifice tube should be at the connection between that tube and the line from the condenser.

If I remember the GM systems correctly, there should be a switch on both the high side and the low side. The low side switch turns the system off if the low side pressure gets too low, for example if the system is undercharged/leaking. The high side switch turns the system off if the high side pressure gets too high.

The low side switch is located on the accumulator, the high side switch should be located somewhere between the compressor and the condenser or soon after the condenser exit.

I could be wrong about the 2 switches...it has been 8 years since I've touched a GM A/C system. However, I can tell you for sure that those switches are NOT interchangeable.

[greenbullitt]

I could be wrong, but i dont see that evap fitting in a mustang case.

no fit=custom lines

[NoClassic]

What year is the base program on your PCM? What year truck did the compressor come from?

The orifice tube is on the high side line coming out of the evaporator, before the accumulator/dryer.

[dville_gt]

I ended up finding out that the expansion valve is located in the pipe that connects to the evaporator, in the line that wraps around the evaporator you can see where the pipe gets larger right at the connection (on the engine side of the connection), the valve is in there.

As for the pressure switch the PCM seems to only be wired for one of those switches, the trucks use a low pressure switch and the cars use a high pressure switch is my understanding, the wiring on the trucks looks something like this:

45 GRY 2700 5 Volt Reference (A/C)
This provides 5 volts to the pressure switch

14 RED/BLK 380 A/C Refrigerant Pressure Sensor Signal (A/C)
This wire tells the PCM the pressure

43 DK GRN/WHT 459 A/C Compressor Clutch Relay Control (A/C)
- This wire drops ground to a relay that will then energize (+) the A/C clutch

80 BLK 2751 Low Reference (A/C)
Basically like a ground, so it can make a perfect calculation of voltage.

Where it becomes interesting is that the A/C request of a 2005 Escalade is a serial request, thankfully I am running a 2004 Express Van PCM that is supposed to use a +12 v request (obviously ideal in my situation as my Mustang wont have a serial request switch). If anyone has access to AllData and can get a pinout for a 2004 Chevy Express Van PM me.

[dville_gt]

So after comparing the pinouts for the 2005 Escalade and the 2004 Chevy Express Van I found some differences.

Since the express van used a different activation mechanism (+12 vs serial) the pinouts for the a/c stuff is different as well. Thank God the pinouts are very close for most of the important stuff because I used the 2005 pinout to make my harness!

So these look like the pinouts I should use:

Pin Color Description
17 Dark Green/White A/C Request (give this +12 volt to turn on a/c)
43 Dark Green/White A/C Compressor Clutch Relay Control (this will provide a ground to the a/c relay)
55 Dark Green A/C Low Pressure
57 Tan Reference


It also seems that the 2004 Express van does not use a 3 wire pressure switch like the 2005 Escalade, from what I have read it looks like the 3 wire acts as both a high pressure and low pressure switch while the two wire is a much more simple on/off style low pressure switch.

[dville_gt]

I could be wrong, but i dont see that evap fitting in a mustang case.

no fit=custom lines

You are right.

(I had to cut the bottom off of the heater box and fiberglass a new bottom since the ls1 evaporator is a totally different size than the fox.

[dville_gt]

Looks like it uses both a low pressure switch and a high pressure switch.

High pressure switch is inline with the +12v from the dash, and the low pressure is inline with the ground wire from the compressor

[greenbullitt]

why not use a fox evap core?

[dville_gt]

why not use a fox evap core?

Main reason was to keep the whole system together, all of it will be gm r134a components. Here is a picture of it after I fiber-glassed it. The final product will obviously be much nicer (need to sand and paint), but it gives you and idea of what was needed. I just cut the bottom of then formed around where the evap was too large, and I made a nook for the pipe that wraps around the evap. It worked out pretty well and I can still remove the evap from the box if needed.



Quick question, what should I glue the heater box back together with?

[BP]

It wouldn't be too terribly difficult to just hotwire the compressor clutch directly to your a/c controller and bypass all of the electronic controls. Pretty sure there is a low pressure switch, a high pressure switch and a evaporatore core temperature sensor. The low pressure switch is fairly critical in that it'll shut off the system if there is a leak and possibly save the compressor. The high pressure switch is there to keep you from blowing a line off or blasting the caps on the compressor if the head pressure gets too high. The system will quit cooling way before that ever happens and hopefully you'd shut it off anyways. The evap temp sensor is to make sure it doesn't freeze over. Keep the box drained properly and the low side pressure in check and it won't be a problem.

Not sure if it'd help but I have a couple HVAC boxes out of 95 Camaros that were stripped into race cars. Everything is there still as removed.

[dville_gt]

It wouldn't be too terribly difficult to just hotwire the compressor clutch directly to your a/c controller and bypass all of the electronic controls. Pretty sure there is a low pressure switch, a high pressure switch and a evaporatore core temperature sensor. The low pressure switch is fairly critical in that it'll shut off the system if there is a leak and possibly save the compressor. The high pressure switch is there to keep you from blowing a line off or blasting the caps on the compressor if the head pressure gets too high. The system will quit cooling way before that ever happens and hopefully you'd shut it off anyways. The evap temp sensor is to make sure it doesn't freeze over. Keep the box drained properly and the low side pressure in check and it won't be a problem.

Not sure if it'd help but I have a couple HVAC boxes out of 95 Camaros that were stripped into race cars. Everything is there still as removed.

Ya, I am trying to figure out where the switches should go. I figure the low pressure goes on the low pressure line leaving the compressor. As for high pressure the only place I can think of would be on the accumulator, but the only port there is the one for manifold gauges. There is no evap sensor.

I appreciate the offer on the heater box, I already have one from an fbody that I cannibalized. In my garage I have 1 fbody heaterbox, 1 fox heaterbox, 1 complete fox dash, and 1 complete gm a/c system. Can't wait for cold air!

[BP]

Ya, I am trying to figure out where the switches should go. I figure the low pressure goes on the low pressure line leaving the compressor. As for high pressure the only place I can think of would be on the accumulator, but the only port there is the one for manifold gauges. There is no evap sensor.
!

On an 04 G-van the high pressure switch is located in the rear of the compressor itself and the low pressure should be on the accumulator, although anywhere in the line between it and the expansion valve would work.

[dville_gt]

On an 04 G-van the high pressure switch is located in the rear of the compressor itself and the low pressure should be on the accumulator, although anywhere in the line between it and the expansion valve would work.

AWESOME info, so obviously I cant run the high pressure switch since the compressor I have does not have a provision for it (2005 Escalade Compressor). For the low side I have 2 ports to choose from (factory location on escalade is right by the compressor and factory on the f-body is on the way to the condensor.

[dville_gt]

AWESOME info, so obviously I cant run the high pressure switch since the compressor I have does not have a provision for it (2005 Escalade Compressor). For the low side I have 2 ports to choose from (factory location on escalade is right by the compressor and factory on the f-body is on the way to the condensor.

Errr. wait, both of the ports for switches I have are high side