Cooling Fan A/C Problem (Need Some Help)
Thread Starter
Burning Brakes
Joined: Aug 2003
Posts: 899
Likes: 0
From: Copperas Cove TX
Cooling Fan A/C Problem (Need Some Help)
Got an 86 Corvette and when I turn my A/C on the engine cooling fan does not come on.....I know there must be a relay that is suppose to turn that fan on........Can anyone help me with this problem????
I have club meeting tonight so will not be here to answer any question till after 9 P.M. central.....
Appreciate you experts help with this............
Have a Great Day!!!!!!!!
I have club meeting tonight so will not be here to answer any question till after 9 P.M. central.....
Appreciate you experts help with this............
Have a Great Day!!!!!!!!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
There's a fan switch on the high pressure (smaller) line from the Condensor to the Evaportor. It opens with head pressures of about 220 psi and that signals the ECM to ground the main fan relay. Once the air flow has dropped the high side to 170 - 190 psi, the contacts close and with a completed ciircuit, the ECM removes ground from the Relay. Test it by disconnecting it. If the fan comes on, the ECM and Relay are good and the switch is either broken or the pressure is too low to reach the threshold (charge it back up). Attach a manifold gage set to confirm it or drop by an a/c shop - shouldn't take more than 10 minutes and a couple of Bucks to find out.
Thread Starter
Burning Brakes
Joined: Aug 2003
Posts: 899
Likes: 0
From: Copperas Cove TX
Originally Posted by SunCr
There's a fan switch on the high pressure (smaller) line from the Condensor to the Evaportor. It opens with head pressures of about 220 psi and that signals the ECM to ground the main fan relay. Once the air flow has dropped the high side to 170 - 190 psi, the contacts close and with a completed ciircuit, the ECM removes ground from the Relay. Test it by disconnecting it. If the fan comes on, the ECM and Relay are good and the switch is either broken or the pressure is too low to reach the threshold (charge it back up). Attach a manifold gage set to confirm it or drop by an a/c shop - shouldn't take more than 10 minutes and a couple of Bucks to find out.
HELP
Have a Great Day!!!!!!!!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
The 2nd switch is the high pressure switch. Normally closed, it opens when the high side reaches 400 psi and that keeps it from blowing up. You want the one next to it, or the switch that doesn't turn off the compressor when you disconnect it. If disconnecting that switch doesn't turn on the fan, the wire is shorted to ground, or the ECM, Relay or Fan is bad. The fan should at least be coming on when you ground the Diagnostic Link. If it isn't, jumper it's leads to ground to make sure that the motor is ok.
Advanced
Joined: Apr 2006
Posts: 60
Likes: 0
The switch that is mounted on your compressor in the back is the one that turns the radiator fan on. I just went through a nightmare of a time finding one for my 84 because it works a little differently than some. I accidently broke it when I was replacing my compresor and put one in that was normally closed when I needed one that was normally open so my fan ran anytime the key was in run. Got a new one last night and now the fan comes on like it should. Once presure increases to over 150 psi after the compressor is running it will turn the fan on. The other 2 switches are the hi/lo compressor cycling switches which control the compressor clutch but not the radiator fan. Again this is how my 84 works but I think they are very similar although the fan cutout switch for the 84 was just for that year. Later years had higher pressure limits. The only down fall to changing it again was I had to give up 2.75lbs of R12 to the recovery unit.
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