Car is 91 V6[3800] FWD Pontiac Gran Prix Problem is electric fan operation. In the middle of summer while at college my son was having overheating problems due to fans not working. He took it to a ASA garage and they diagonozed it to be low AC freon pressure.Because this pressure was low the fans would not activate until the freon level was brought back up to proper pressure.They filled the freon to proper pressure and they were right the fans once again function right. Now we are again having trouble with the fans again not turning on.I think the freon has once again leaked out to a pressure low enough to cause this problem again. Since he's not to concerned with having AC in summer anyway and it probly looks like a huge repair bill to replace the leaking AC compressor and recharge it again I would like to bypass whatever operates the fans thru the AC. Anyone help me out here or point me to something I can study.
I don't understand why the fans would not turn on if the freon level is low, design wise this makes no sense to me. Anyway if this is true then the power to the fans has to be routed through a normally open pressure switch that the freon pressure in the system keeps closed all the time. When the freon pressure gets down to low the switch returns to it's normal position (open) and the fans won't run. Still don't know why the hell a manufacturer would do that, make your car overheat to let you know that the freon is low???? If it uses 134a just put some more in yourself, it's easy and cheap. Dave Berryo No:
Sounds like something stupid that a treehugger came up with. If your leaking freeon it kinda forces you to get it fixed so the car can run again.....just another stupid thing some treehugger came up with. . Then again on the other hand...the fans should go on either way with or without freeon....are you sure its not the fan temp switch....just something to check:TU: Larry
Try this.... Don't see a 3800 listed in the '91 service manual ( vin's D, T, and X), but you might try grounding terminal "B" of the ALDL connector. Fan should run with key on and terminal "B" grounded, but you can't drive it this way because you'll be in "diagnostic mode". Wires at the primary fan relay(left side, behind radiator, according to service manual, but they've lied to me before.) are; 1; battery feed (red) 2; black/red to fan motor 3; dark green and white that the ECM grounds to power the relay and turn the primary fan on. Jumping the red to black/red will supply battery voltage (but not switched voltage) to the primary fan. Ground the green/white wire- the fan should run any time the key is turned on. Hope this helps. Fan comes on with AC to move adequate air through condensor at speeds slower than 40 mph.
Dave you might try over at WWW.TURBOBUICK.COM They have a 3800 tech forum over there, they maybe can tell you how to bypass it, cause they are modifing those SC 3800's to run 12's, Mods like the GN's get ,including overriding the coolant fan for you to control. hope this helps :grin:
Dwayne Makes sense that the fans would come on when ever the air comes on, but that should be a seperate circuit than the temp control fan switch, in parallell with, so that either circuit can start the fans. Dave Berryou: ou:
You're right They are supposed to turn on when the ECM sees 227'F. (with the A/C/ off). I've seen as high as 230' and up. Also, the ECM reading is almost always as much as 10'F (or more) less than what the factory gauge is showing. Takes a while for coolant temp to get that high when your not setting in bumper to bumper traffic and 90% humidity/ 90' temps.
