LSx in Fox body A/C help
Since you guys are all talking about the A/C system...I thought Ide toss a question about controlling the A/C with the PCM. My swap is in an 87 Trans AM. I only remember seeing one sensor off the 99 swap parts that I removed. I think it was in the low side...but I cant remember.
1. Where is the high side sensor?
2. What do I do for the A/C request? Just run a signal that normally went to my compressor to the PCM? A 12-volt signal? Then the PCM takes care of everything else...?
Brains: Im doing the same thing with the evaporator. I pulled my 3rd gen one out and compared it to the 4th gen. Looks like I might have to extend the evap box alittle bit...shouldnt be too hard with some fiberglass or something along those lines. I was thinking about grafting the front of the 4th gen box onto mine. Anyway...good idea! No custom lines, its all designed to go together...should be more efficient.
Justin
1. Where is the high side sensor?
2. What do I do for the A/C request? Just run a signal that normally went to my compressor to the PCM? A 12-volt signal? Then the PCM takes care of everything else...?
Brains: Im doing the same thing with the evaporator. I pulled my 3rd gen one out and compared it to the 4th gen. Looks like I might have to extend the evap box alittle bit...shouldnt be too hard with some fiberglass or something along those lines. I was thinking about grafting the front of the 4th gen box onto mine. Anyway...good idea! No custom lines, its all designed to go together...should be more efficient.
Justin
1. There's only one sensor, in the high pressure (3/16" aluminum) line right in front of the orifice tube. Since the orifice is a fixed size, the PCM only needs to know the high pressure to know when to cycle the compressor.
2. I can't remember if the A/C request wire to the PCM was a +12V trigger or a Gnd trigger. Easy enough to tell which, just hook up a scan tool and play with the request wire
Once you take care of that wire, you are correct - the PCM handles everything else, including turning on the fans.
Doing the fiberglass work on the airbox was the easiest way for me to put A/C in the car, and not futz around with fittings, pressures, etc. With everything mounted in the car now, it honestly looks factory as well. Can't wait to charge the system, and fire up the motor to see how well it works
2. I can't remember if the A/C request wire to the PCM was a +12V trigger or a Gnd trigger. Easy enough to tell which, just hook up a scan tool and play with the request wire
Once you take care of that wire, you are correct - the PCM handles everything else, including turning on the fans.Doing the fiberglass work on the airbox was the easiest way for me to put A/C in the car, and not futz around with fittings, pressures, etc. With everything mounted in the car now, it honestly looks factory as well. Can't wait to charge the system, and fire up the motor to see how well it works
Cool so there is only one sensor... The simplicity of these things really amazes me the more and more I get into my swap.
So you used fiberglass to re-work your box? I was going to do that or use some aluminum strips with sealant and pop rivets. Not my first choice...but Ive never used fiberglass before.
Brains do you have any pics of your modified HVAC box where you fiberglassed it? Or havent you re-worked it yet? My motor is coming out within the next couple days, so I figured Ide work on that while its out so I have more room.
As for that request wire...I dont have a scan tool yet. Ill have to figure out if it needs power or a ground...and if its 12v or some other lower votage signal.
Justin
So you used fiberglass to re-work your box? I was going to do that or use some aluminum strips with sealant and pop rivets. Not my first choice...but Ive never used fiberglass before.
Brains do you have any pics of your modified HVAC box where you fiberglassed it? Or havent you re-worked it yet? My motor is coming out within the next couple days, so I figured Ide work on that while its out so I have more room.
As for that request wire...I dont have a scan tool yet. Ill have to figure out if it needs power or a ground...and if its 12v or some other lower votage signal.
Justin
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
Fiberglass is not that difficult to work with, especially if you don`t have to make sharp corners with it. Just mix it according to the directions on the can, you can use a little less harndener if you are worried about it setting up too fast. Then use a paint brush to soak the cloth. You can either put the resin on the cloth on a piece if tinfoil and then transfer it to the surface or just put the resin on with the cloth in place, you want to use a light stabbing motion with the brush as you apply the resin to make sure it gets all the way through the cloth. The cloth should end up looking wet with an even sheen accross it. You want to put on at least 2 layers at a time and usually no more than 4 layers of cloth at a time. For a heater box I would use 3-4 layers total unless it was a highly stressed area. For the form to hold the cloth in place while it dries you just need to get inventive if you are using fiberglass to span large spaces, the form can be very elaborate or very simple. I use wax paper to go up against the fiberglass so that it is easy to use. To hold the wax paper up I can sometimes get away with bending a piece of cardboard to shape, or wedging newspaper ***** in the space, or even building the shape out of modeling clay. Oh and you should probably wear gloves so that you don`t get the resin stuck to your hands, but I would ditch the cheap plastic gloves if you get a kit, they tend to stick to the fiberglass and make a mess 
. Latex or nitrile gloves work a lot better.
. Latex or nitrile gloves work a lot better. Hey thanks for the pics and advice! Brains, it looks like you just used the fiber glass to re-make the end of the box. Is it possible to use the fiberglass to join two parts together? As in grafting the front of my 4th gen box to my 3rd gen box.
Will you sand down the glass to make it smoother? Or just paint over it like it is? I guess Ill pick up one of those kits and maybe practice on something to see how it sets up and how it holds. Does it actually adhere to the surfaces once set?...sort of like an epoxy? Sorry for the "newbie type questions"...I can probably find a ton of stuff if I search alittle. Im pretty excited that this is going to work out though. One less thing to have custom made (a/c hoses).
Justin
Will you sand down the glass to make it smoother? Or just paint over it like it is? I guess Ill pick up one of those kits and maybe practice on something to see how it sets up and how it holds. Does it actually adhere to the surfaces once set?...sort of like an epoxy? Sorry for the "newbie type questions"...I can probably find a ton of stuff if I search alittle. Im pretty excited that this is going to work out though. One less thing to have custom made (a/c hoses).
Justin
Sorry to jack the thread, but I think it is related enough to be helpful. I'm in the same situation w/ regards to contolling the a/c system via the stock pcm and would like some clarification on a few things. (I'm using a 2002 pcm from a truck). The pinouts for the truck pcm a/c control are (see below and attached diagram):
C2 (Red connector)
pin 11 ac high pressure recirculation switch signal
pin 17 ac request signal
pin 43 ac compressor clutch relay control
pin 55 ac low pressure switch signal
1. Does the pcm require a ground at pin 55 on the red connector to cycle the compressor?
2. If so and if I'm not running the low pressure switch, can I just run it to ground?
3. What is the function of the "high pressure recirculation switch" signal that goes to pin 11 on the red connector?
4. Is this necessary to cycle the compressor?
help
C2 (Red connector)
pin 11 ac high pressure recirculation switch signal
pin 17 ac request signal
pin 43 ac compressor clutch relay control
pin 55 ac low pressure switch signal
1. Does the pcm require a ground at pin 55 on the red connector to cycle the compressor?
2. If so and if I'm not running the low pressure switch, can I just run it to ground?
3. What is the function of the "high pressure recirculation switch" signal that goes to pin 11 on the red connector?
4. Is this necessary to cycle the compressor?
help
"Recirculation Actuator The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in defrost. When the mode is in defog, Recirculation will only be available for 10 minutes. The operator must activate the blower for Recirculation operation. The A/C high-pressure recirculation switch can cause the HVAC system to recirculate air. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times. When the high side pressure reaches 2206-2620 Kpa (320-380 psi), the PCM will place the HVAC system in recirculation mode. The high side pressure is lowered when the inside air cools the refrigerant within the A/C evaporator. When the high-side pressure reaches 1447-1861 Kpa (210-270 psi), the PCM will place the HVAC system out of recirculation mode."
It looks to me like the high pressure recirculation switch is not needed for AC operation. It just turns the compressor off while the A/C is in recirc or max mode.
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