Fan does not come on with the a/c
Thread Starter
Teching In
Joined: Jun 2011
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Fan does not come on with the a/c Hello all after searching and searching I figured I would just ask.
I swapped a 5.3 into a 67 nova with vintage air. I'm using a 2001 Camaro ECM. I wired the A/C request wire to the power wire that goes to the clutch so when I turn on the A/C it sends 12 volts to A/C request on the ECM. The compressor comes on and cools but it doesn't start my fan. I know a guy running a 2000 Camaro ECM and this is how he has it wired and working. My tuner said it needs to see pressure from a pressure switch so tell the ECM to turn on the fans. If this is true is there a way I can "trick" it so when I turn on the AC it starts the fan? I have a vintage air pressure/safety switch in the system to shut off the compressor in case of to low or high of pressure.
Any help is appreciated...
PS
My tuner tried to lower the set pressure from 210 psi to 0 and the fans still didn't work
I swapped a 5.3 into a 67 nova with vintage air. I'm using a 2001 Camaro ECM. I wired the A/C request wire to the power wire that goes to the clutch so when I turn on the A/C it sends 12 volts to A/C request on the ECM. The compressor comes on and cools but it doesn't start my fan. I know a guy running a 2000 Camaro ECM and this is how he has it wired and working. My tuner said it needs to see pressure from a pressure switch so tell the ECM to turn on the fans. If this is true is there a way I can "trick" it so when I turn on the AC it starts the fan? I have a vintage air pressure/safety switch in the system to shut off the compressor in case of to low or high of pressure.
Any help is appreciated...
PS
My tuner tried to lower the set pressure from 210 psi to 0 and the fans still didn't work
Joined: Sep 2004
Posts: 3,148
Likes: 12
From: Downers Grove, IL
Well I don`t have any hard evidence but heres my hypothesis. The 99-02 camaro and 99-02 trucks use the same physical PCM, only the programming is different. The 99-02 tucks only need 2 signals to engage the fans (+12v to red pin #17 and a ground to red pin #55). which is how I have mine wired. But when I check my programming in hptuners in the fans section it still lists my fan turn on pressure as 215 psi even though my motor never had an a/c pressure sensor
The f-bodies use red pin #17 also, however it also uses red pin #18 to sense when the a/c clutch actually gets voltage (this pin is unused on the trucks). The f-bodies also have a pressure sensor input going to red pin #14 (which is unused on the trucks)
My guess is that if you put +12v to red pin 17 and a ground to red pin#55 and treat your camaro PCM as if it were a truck PCM it will probably work to engage the fans, however, I have no proof its only a guess.
The f-bodies use red pin #17 also, however it also uses red pin #18 to sense when the a/c clutch actually gets voltage (this pin is unused on the trucks). The f-bodies also have a pressure sensor input going to red pin #14 (which is unused on the trucks)
My guess is that if you put +12v to red pin 17 and a ground to red pin#55 and treat your camaro PCM as if it were a truck PCM it will probably work to engage the fans, however, I have no proof its only a guess.
TECH Regular
Joined: Sep 2007
Posts: 443
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From: Kansas City, MO
If you don't have a 3 wire pressure sensor and just a 2 wire low pressure switch, you need to do this: Program the PCM with the VIN and tune from an 02 silverado. Copy over the differences in your tune to the truck tune and it'll work. Assuming everything is wired correctly. It'll also cost 2 credits with hptuners, but it works. Just ran into a similar situation on an s10 I tuned that we started off with an fbody tune.
Thread Starter
Teching In
Joined: Jun 2011
Posts: 6
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If you don't have a 3 wire pressure sensor and just a 2 wire low pressure switch, you need to do this: Program the PCM with the VIN and tune from an 02 silverado. Copy over the differences in your tune to the truck tune and it'll work. Assuming everything is wired correctly. It'll also cost 2 credits with hptuners, but it works. Just ran into a similar situation on an s10 I tuned that we started off with an fbody tune.
I was really hoping for the send power here add a diode there fix. thats been tested.
TECH Resident
Joined: Nov 2007
Posts: 816
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From: Texas
You can use 2 relays in series to accomplish this. I am not using the ecm in my system at all but it does turn on the fans when the engine reaches the high or low temp settings. So I wired 2 relays in series that will activate the fans when I turn on the a/c. The relays create an isolated circuit so that the a/c does not get turned on when the ecm kicks the fans on and a/c is not being used.
everything is wired for a 2001 Camaro not the silverado so I think if I made the ecm think it was a silverado I would have more issues? One of the replacement ECM's was a 2002 silverado ECM I sent it back cause my tuner doesn't have a lic. for it. I will talk to the tuner and see what he thinks about it.
I was really hoping for the send power here add a diode there fix. thats been tested.
I was really hoping for the send power here add a diode there fix. thats been tested.
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Thread Starter
Teching In
Joined: Jun 2011
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Ok I got it working...
What I did is I hooked up the a/c clutch status wire to the a/c request wire that way when you turn on the a/c it sends 12 volts to the request and the clutch status wire. there is a short delay when you turn on the a/c but then the fans come on on high. Then when you shut off the a/c they shut off after 30 seconds or so. thank god.....
What I did is I hooked up the a/c clutch status wire to the a/c request wire that way when you turn on the a/c it sends 12 volts to the request and the clutch status wire. there is a short delay when you turn on the a/c but then the fans come on on high. Then when you shut off the a/c they shut off after 30 seconds or so. thank god.....
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