Penglii Posted October 15, 2009 Report Share Posted October 15, 2009 I have a 1994 Grand Prix SE 3100 and the cooling fans do not work correctly. The fans never activate. Not when the coolant temp gets plenty high, and not when the A/C is on. The A/C appears to function correctly, it outputs cold air anyway... it just does not activate the fans, not even with everything on full blast and the engine warmed up. I popped the covers of both fan relays, and pushed the switches with a toothpick... which DID activate the fans So I assume the relays are good, and the fans are good too. So... I am stumped regarding what to test next. Since it is a 94, with the OBD1.5 crippled ALDL port, I cannot short the PCM to find out if that would activate the fans. I would not think the Coolant Temp Sensor / Thermostat would be to blame, because the A/C does not activate the fans either. Clearly the problem is that the PCM is not getting a signal to the relays... but without the ALDL paperclip trick ability, how can I check that? Could disconnecting the battery for a few hours remedy the problem? I don't want to start pulling the car apart to test sensors and connections before knowing if the PCM is simply crapping out. Likewise I don't want to replace the computer if it is simply a sensor or two to blame. Quote Link to comment Share on other sites More sharing options...
DavidHowell3633 Posted October 15, 2009 Report Share Posted October 15, 2009 If memory serves, there's the coolant temperature sensor and the AC hi pressure switch that both have to function for both fans to work automagically. On my 95, they just decided to one day begin working again. This is after I had rigged a switch to make them work for some time. I have since removed the switch. I can't say for sure, but I think the ECM get confused and then gets confused that it's confused. If this were Microsoft, I would ask, have you rebooted? So, and I doubt this will really help, disconnect the battery and let it sleep for 30 minutes or so. See if that helps. Besides the wiring schematic, you'll need chicken bones and tea leaves to cast out those evil demons. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted October 15, 2009 Report Share Posted October 15, 2009 the turn on temperature for the fans when the a/c if off is about 230 degrees F, and with the a/c on, about 215degrees F. I would not be surprised if you cannot observe the fans turn on in this cold weather. Quote Link to comment Share on other sites More sharing options...
DavidHowell3633 Posted October 16, 2009 Report Share Posted October 16, 2009 My nephew came over with the same complaint on his 91 CS. I told him to crank it up and we stood there talking for 20 minutes- then, the fans came on. Problem solved. Quote Link to comment Share on other sites More sharing options...
Penglii Posted October 16, 2009 Author Report Share Posted October 16, 2009 @DavidHowell3633: Thanks for the tip, I will try disconnecting the battery when I hopefully have some free time this weekend. If that does not help then I'll look closer at the coolant temp sensor and the A/C pressure switch. @Crazy K: Those numbers and the cool weather both make sense, but I think I am taking that into account in my diagnostics. The IP temp gauge can point somewhere between the 3/4 mark and the danger zone, and neither fan is activated even if I then crank the A/C to full blast. When I get home from work tonight, before I do anything else, I'll let it idle for a good 20 minutes, see what happens, and follow up here with the results. Quote Link to comment Share on other sites More sharing options...
KingVee Posted October 17, 2009 Report Share Posted October 17, 2009 Sounds like the coolant temperature sensor/sending unit, I had the same problem on my 2.8L MFI. A switch had been permanently installed by the previous owners to turn the fan on manually - that without a functional temperature gauge. I heard this is a common problem on 60°s. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted October 17, 2009 Report Share Posted October 17, 2009 results? a good idea would be to block the radiator with cardboard, and i would not trust an unverified gauge temperature reading to be accurate... because often they aren't. I've seen either sensor to be bad and cause an issue. There are two temperature sensors on your motor (and any 1995 and earlier 60degreeV6): the ECM sensor is located by the thermostat, and is a two wire. the gauge/idiot light sensor is located on the driver's side corner of the rear head, and is a single green wire. either is cheap enough to buy and install. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 17, 2009 Report Share Posted October 17, 2009 results? a good idea would be to block the radiator with cardboard, and i would not trust an unverified gauge temperature reading to be accurate... because often they aren't. I've seen either sensor to be bad and cause an issue. There are two temperature sensors on your motor (and any 1995 and earlier 60degreeV6): the ECM sensor is located by the thermostat, and is a two wire. the gauge/idiot light sensor is located on the driver's side corner of the rear head, and is a single green wire. either is cheap enough to buy and install. X2, Crazy K wins again. Quote Link to comment Share on other sites More sharing options...
Penglii Posted October 17, 2009 Author Report Share Posted October 17, 2009 @CrazyK: I never did get to let it idle for a half hour to verify the fan activation. On my way home from work the upper radiator hose suffered a blowout. Coolant started spurting out of a hole in the side of the hose... coolant was landing on the exhaust manifold heat shield and boiling away in a cloud of white. I was able to stop right away before I ran out of coolant or overheated, and right now the car is getting the hoses replaced and the radiator flushed. I get the feeling that is gonna solve my problems. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted October 17, 2009 Report Share Posted October 17, 2009 hopefully! Quote Link to comment Share on other sites More sharing options...
Penglii Posted October 18, 2009 Author Report Share Posted October 18, 2009 I'll find out sometime on Monday. Funny story... after the radiator hose committed Seppuku on Friday afternoon, I carefully drove it to the local trustworthy shop and then walked the mile or so home. I should note that since I have had the car I have experienced zero mystifying electrical gremlins (cooling fans aside). Mechanic took a quick look at it - in their parking lot - and then closed up shop for the day. This morning they go to start it and pull it into their shop, battery was dead and they had to jump it to get it going. They proceed to replace the radiator hose and flush the system. They give me a call letting me know the battery needs to be replaced too, and asked me if I had been having any problems starting the car or with the battery... I tell them that I have had no such problems but they could go ahead and replace the battery if it is shot... they tell me I can stop by in a half hour to pick up my car. I get there and the tech said, to paraphrase: "Umm... I don't know what is wrong with your car, we thought the battery was dead but the new one is not working either. We had your repair complete and the car was running great, with the new battery in, then we shut it off until you got here. Now it won't start. We are so sorry, we don't know what happened, but you are not getting your car back today. We will give you a call on Monday." So I think the shop forgot to use the correct chicken bones and tea leaves! LOL I wonder what went wrong though... did they feed the gremlens after midnight and give them a bath? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 18, 2009 Report Share Posted October 18, 2009 So I think the shop forgot to use the correct chicken bones and tea leaves! LOL I wonder what went wrong though... did they feed the gremlens after midnight and give them a bath? that is the only reasonable explanation. unfortunately i have not studied anti-voodoo, so i can't help with that. though i would suggest taking a multimeter and seeing how much of a draw there is on the battery when the vehicle is off. .03 amps would be normal... Quote Link to comment Share on other sites More sharing options...
GP1138 Posted October 18, 2009 Report Share Posted October 18, 2009 Tell them to check the auxiliary positive post nut. Quote Link to comment Share on other sites More sharing options...
Penglii Posted October 23, 2009 Author Report Share Posted October 23, 2009 Sorry for the delay in the update. It appears that the cooling fans operate correctly now The battery wires have been replaced, including the aux pos terminal, and the battery itself... and of course the blown out radiator hose. I believe the radiator has been properly bled of air bubbles after being refilled too. With good wiring and functional hoses the cooling system is back to good functioning status again. The temp gauge will now rise to slightly below the 3/4 mark, which must be 230*F, and the fan circuit will engage. Thanks for all the help, it has all been very useful. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.