Modern AC in Chevelle
Modern AC in Chevelle I am in the middle of installing a 6.0 vortec engine into my 1970 Chevelle. I have been going back and forth on wether or not to install the AC system. The car had AC when I bought it but I want to use the vortec's stock compressor and a Camaro condenser.
If I use the compressor, what electrical connections do I need to keep? I know I will need the clutch switch but do I need anything else? Does the computer control the AC?
What is the best way to connect the Chevelle's stock AC box the the modern LSX parts?
Thanks,
David
If I use the compressor, what electrical connections do I need to keep? I know I will need the clutch switch but do I need anything else? Does the computer control the AC?
What is the best way to connect the Chevelle's stock AC box the the modern LSX parts?
Thanks,
David
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From: ocala,fl--- forest-ocklawaha
i thought bout this too.. but using a 2000 silverado whole cooling system.. everything, pretty much.. id use just push botton or something to engaged the ac comp..
I installed and used the LS1 compressor with my factory Chevelle setup.. just wired the compressor up like factory Chevelle and grounded the other wire.
Took both sets of hoses/tubes to a Tubing and Hose shop and we came up with a set hoses and tubes that connected the old with the new.
Only problem I have is that the LS1 compressor is a variable dispalacement and doesn't goto 100... so it is not 100 % capacity, but it is cold as long as I keep moving or not in bumper to bumper traffic.
Took both sets of hoses/tubes to a Tubing and Hose shop and we came up with a set hoses and tubes that connected the old with the new.
Only problem I have is that the LS1 compressor is a variable dispalacement and doesn't goto 100... so it is not 100 % capacity, but it is cold as long as I keep moving or not in bumper to bumper traffic.
What year/make/model PCM are you using? At some point in the early-mid 2000's, many of the trucks went from a single "on/off" A/C request wire to A/C request via the serial data system.
Joined: Sep 2004
Posts: 3,148
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From: Downers Grove, IL
Looks like you are using a 2001 6.0L truck engine and compressor with the red/blue PCM. So you are all set. If you are using the truck underhood fuse center I would hook the 12v A/C request wire from your dash to red pin #17 on your PCM. Hook one side of a low pressure switch to ground and the other to red pin #55 on the PCM. (I`m not sure if a 70 chevelle had a low pressure switch or low temp switch, but I can`t seem to find A/C wiring diagrams for it).
Luckily you have a truck compressor which should be a 10s20f or 10s17f delphi compressor which is fixed displacement like your original chevelle compressor. The only thing I have noticed with the newer compressors like that is they do not have a linear output curve like the old axial compressors on your chevelle. The newer compressors seem to flow substantially more freon at high RPM than at idle, where as the old axials seemed to flow the same amount no matter what RPM. When you charge the system make sure that there is sufficient pressure on the low side at your motors highway cruising RPM to prevent it from cycling the compressor or freezing up (~28psi low side) The flip side of that is I usually end up with 38-40psi on the low side at idle which is why the A/C seems warm at idle.
Luckily you have a truck compressor which should be a 10s20f or 10s17f delphi compressor which is fixed displacement like your original chevelle compressor. The only thing I have noticed with the newer compressors like that is they do not have a linear output curve like the old axial compressors on your chevelle. The newer compressors seem to flow substantially more freon at high RPM than at idle, where as the old axials seemed to flow the same amount no matter what RPM. When you charge the system make sure that there is sufficient pressure on the low side at your motors highway cruising RPM to prevent it from cycling the compressor or freezing up (~28psi low side) The flip side of that is I usually end up with 38-40psi on the low side at idle which is why the A/C seems warm at idle.
I installed and used the LS1 compressor with my factory Chevelle setup.. just wired the compressor up like factory Chevelle and grounded the other wire.
Took both sets of hoses/tubes to a Tubing and Hose shop and we came up with a set hoses and tubes that connected the old with the new.
Only problem I have is that the LS1 compressor is a variable dispalacement and doesn't goto 100... so it is not 100 % capacity, but it is cold as long as I keep moving or not in bumper to bumper traffic.
Took both sets of hoses/tubes to a Tubing and Hose shop and we came up with a set hoses and tubes that connected the old with the new.
Only problem I have is that the LS1 compressor is a variable dispalacement and doesn't goto 100... so it is not 100 % capacity, but it is cold as long as I keep moving or not in bumper to bumper traffic.
OP. if you want to get creative, you can take the whole A/ C system out of a late model and incorporate it into the original box. The link to my 72 shortbed build in my sig shows how I took all of a 2003 Silverado A/C system and put it in the modified original box. It worked great, but it was alot of work to get it all in there.
Looks like you are using a 2001 6.0L truck engine and compressor with the red/blue PCM. So you are all set. If you are using the truck underhood fuse center I would hook the 12v A/C request wire from your dash to red pin #17 on your PCM. Hook one side of a low pressure switch to ground and the other to red pin #55 on the PCM. (I`m not sure if a 70 chevelle had a low pressure switch or low temp switch, but I can`t seem to find A/C wiring diagrams for it).
Luckily you have a truck compressor which should be a 10s20f or 10s17f delphi compressor which is fixed displacement like your original chevelle compressor. The only thing I have noticed with the newer compressors like that is they do not have a linear output curve like the old axial compressors on your chevelle. The newer compressors seem to flow substantially more freon at high RPM than at idle, where as the old axials seemed to flow the same amount no matter what RPM. When you charge the system make sure that there is sufficient pressure on the low side at your motors highway cruising RPM to prevent it from cycling the compressor or freezing up (~28psi low side) The flip side of that is I usually end up with 38-40psi on the low side at idle which is why the A/C seems warm at idle.
Luckily you have a truck compressor which should be a 10s20f or 10s17f delphi compressor which is fixed displacement like your original chevelle compressor. The only thing I have noticed with the newer compressors like that is they do not have a linear output curve like the old axial compressors on your chevelle. The newer compressors seem to flow substantially more freon at high RPM than at idle, where as the old axials seemed to flow the same amount no matter what RPM. When you charge the system make sure that there is sufficient pressure on the low side at your motors highway cruising RPM to prevent it from cycling the compressor or freezing up (~28psi low side) The flip side of that is I usually end up with 38-40psi on the low side at idle which is why the A/C seems warm at idle.
Originally Posted by ls1nova71
OP. if you want to get creative, you can take the whole A/ C system out of a late model and incorporate it into the original box. The link to my 72 shortbed build in my sig shows how I took all of a 2003 Silverado A/C system and put it in the modified original box. It worked great, but it was alot of work to get it all in there.
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Teching In
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From: NW Houston-TX
I am having a problem with this on my car now. My a/c request wire is Teed into the a/c exciter wire going to the clutch and I thought that would be good enough, but now my ECM won't add air at idle so it surges and dies because it's looking for the high pressure sensor and doesn't see it. I recommend doing your best to give the ECM what it needs as far as a/c signals so it will not give you idle troubles like it is me. My ECM is a 2001 Formula.
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Verdad Gallardo The evaporator is the only thing that is in an A/C box, the accumulator is right outside the box, and of course the condenser is in front of the radiator.
The second plug on the compressor if I remember correctly is the high pressure cut out switch, they stopped using them in 2003 on the trucks, so I'm going to assume yours is a '99-'02? That is the easiest system to wire up.
The evaporator is the only thing that is in an A/C box, the accumulator is right outside the box, and of course the condenser is in front of the radiator.
The evaporator is the only thing that is in an A/C box, the accumulator is right outside the box, and of course the condenser is in front of the radiator.
I'm going to follow this also. I installed a 2005 5.3 into my 1972 Jimmy and want to just have my 1972 AC switch energize the compressor clutch. I believe they make an updated POA that will work. Do I just need to have a pressure switch installed in the line? LS1Nova I am going to read your write up but I really want to use my stock AC controller and evaporator if at all possible. I have read that cross flow condensors help quite a bit?
Joined: Sep 2004
Posts: 3,148
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From: Downers Grove, IL
The compressor could be wired directly to the chevelles harness.....but I would make sure that you at least give the PCM an a/c request signal so it bumps the idle up and turns the electric fans on if your running electric fans.
1. The chevelle's "AC on" wire should be connected to the red connector's pin 17 "AC request signal." The computer then does its thing and then the wire goes out of pin 43 on the red connector "AC clutch relay control" to the compressor clutch. Or does it have to go through a relay before going to the compressor?
2. Is the high pressure cut out switch system controlled by the ecu? (in other words, can I just leave the connector alone and just plug it back into the compressor?)
3. Other than that, I guess the blower motor is the only other externally wired part of the system. I am assuming it has to go through a relay for power, right?
I'm going to follow this also. I installed a 2005 5.3 into my 1972 Jimmy and want to just have my 1972 AC switch energize the compressor clutch. I believe they make an updated POA that will work. Do I just need to have a pressure switch installed in the line? LS1Nova I am going to read your write up but I really want to use my stock AC controller and evaporator if at all possible. I have read that cross flow condensors help quite a bit?
I've been using lt1swap.com for the wiring harness information so I am going off of what is on that website. I think I have the wiring figured out but I just want to be sure:
1. The chevelle's "AC on" wire should be connected to the red connector's pin 17 "AC request signal." The computer then does its thing and then the wire goes out of pin 43 on the red connector "AC clutch relay control" to the compressor clutch. Or does it have to go through a relay before going to the compressor?
2. Is the high pressure cut out switch system controlled by the ecu? (in other words, can I just leave the connector alone and just plug it back into the compressor?)
3. Other than that, I guess the blower motor is the only other externally wired part of the system. I am assuming it has to go through a relay for power, right?
1. The chevelle's "AC on" wire should be connected to the red connector's pin 17 "AC request signal." The computer then does its thing and then the wire goes out of pin 43 on the red connector "AC clutch relay control" to the compressor clutch. Or does it have to go through a relay before going to the compressor?
2. Is the high pressure cut out switch system controlled by the ecu? (in other words, can I just leave the connector alone and just plug it back into the compressor?)
3. Other than that, I guess the blower motor is the only other externally wired part of the system. I am assuming it has to go through a relay for power, right?
The blower only has a high speed fan relay, low and medium go straight from the blower switch.
Joined: Sep 2004
Posts: 3,148
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From: Downers Grove, IL
Yep the a/c clutch control from the PCM must have a relay on it.
The high pressure switch is wired in between your chevelle wiring and your PCM pin 17.
The low pressure switch is wired between ground and red pin 55 on the pcm.
The high pressure switch is wired in between your chevelle wiring and your PCM pin 17.
The low pressure switch is wired between ground and red pin 55 on the pcm.
Teching In
Joined: Feb 2008
Posts: 13
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From: Casa Grande, Az
I'm following this too, to make sure I set mine up correctly. It's a 2000 LS1 from a Camaro going into a 70 Chevelle. Having just sorted the wiring, with some questions left over.
The A/C clutch wire on mine runs from the dash to a factory splice that goes to the A/c clutch and pin 18 A/C clutch status. I'm guessing this is different from the way the trucks are wired.
Does it also need to have A/C request pin 17? Can these 17 and 18 be tied together, or are they meant for different things? I'm going to run a Vintage Air system? Does the computer need any other hookups from the A/C?
The A/C clutch wire on mine runs from the dash to a factory splice that goes to the A/c clutch and pin 18 A/C clutch status. I'm guessing this is different from the way the trucks are wired.
Does it also need to have A/C request pin 17? Can these 17 and 18 be tied together, or are they meant for different things? I'm going to run a Vintage Air system? Does the computer need any other hookups from the A/C?
Those updated POA'a or POA eliminators have a low pressure switch in them, but I've never had any luck with them. They rely solely on the expansion valve and cycle the compressor clutch versus running constantly. That said, what compre ssor are you using? The 2005 will have a serial data a/c request, so you will most likley need to bypass the PCM. Just run the original wire coming from the a/c controls to the low pressure switch and from there it goes to the a/c clutch. I hear Tunercat has the ability to change the request type but haven't tried it yet.
I don't want to have any PCM connection at all. I just want the AC switch on my dashboard controls to send 12 volts to the compressor clutch or pressure switch?
I presently have the compressor that came from the 2005 suburban that my engine came out of.
Just trying to get all my info before I buy anything (or even try bolting in my compressor).
Thanks for the help
So the Chevelle's ac control wire would go through the high pressure switch and then to the pcm? Is the high pressure switch located on the compressor itself? If so, where is the low pressure switch?
I just wanted to say that I really appreciate all of the help so far. I am 17 and I have had absolutely no experience with ac so please forgive all of my stupid questions.