AC Cooling fan interaction
07-29-2021, 10:15 PM
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AC Cooling fan interaction
Alright, ill try to be thorough with the description of my issue, and hopefully you guys can help me out.
1986 944na. LHD
Hit a raccoon about a week ago at around 60mph, hit the front right valence, busted foglight, and bent a couple of the brackets the valence bolts onto.
Get home and take off the valence, go to straighten one of the brackets in front, and accidentally puncture my condenser (not a good moment), emptying my ac system of the R-134.
Go to take it for a quick drive, as it still runs and drives fine, and upon idling up my driveway, I notice that my temp is creeping up and up, and no fans coming on (they had been working perfectly prior to the raccoon run-in)
Well ****. After performing Clark's test by jumping the pins on the plug that goes into the thermoswitch, all signs point to the thermoswitch being bad: relay passed with flying colors, turned the fans on and off as it should.
Replaced the thermoswitch the other day, and fans are still not coming on, even when idling up over the second white line on the temp gauge.
I know my fans physically work, I know my relay passed the Clarks test, although maybe it could still be bad (although that would seem unlikely to me), my coolant system is bled well with no air bubbles, and I have a new thermoswitch installed.
in my mind, it can't be a coincidence that my fans stopped right after hitting the raccoon, and emptying my AC system (oops). Given that none of the fan wiring runs on the right side of my car, I don't really see how the impact would have affected my fan's functionality. I also don't understand how emptying my AC system would have led to the fans not working, as it is a separate system. (fans do still turn on at low speed when I turn the AC on). Currently when cruising on the highway, in 85F temps, my temp stays right above the first line on the temp gauge, so stays in a normal range as long as I am moving.
I am beginning to think the thermoswitch I put in could maybe be bad, because if the clarks method of testing the plug by jumping it shows that everything down the line from the thermoswitch is doing its job, that would point back to the thermoswitch being the issue. I am having my ac serviced this Thursday, but I don't expect my fans to come back on when my AC is fixed.
Hopefully someone could shed some light on any ideas of what my issue may be, or have input for how to run tests to find whats wrong. Thanks
EDIT*****
Got my AC serviced, and back from the shop. I had the thermoswitch plug jumpered when I took it in to run the fans on high with the key on, and when I got the car back, and turned on the key, only the passenger side fan was on, and barely turning, so I quickly took out the jumper. When I turned on the AC, only the passenger fan ran. Got it home, and went to use clarks method to test the fans. Relay failed the part where you jumper the 2 and 3 plug spots, as instead of both fans coming on, only the passenger side came on. Relay passed the other tests. Fans still won't come on to cool the car even when idling up to the red. The weird part is, if I turn the car on and let it run, and turn the ac on, the passenger side fan runs, and the driver side fan comes on and off, on for maybe 10 seconds, and then off for 10. Is that normal fan operation for when the AC is on? I thought they were both supposed to turn on at the same time.
Overall, it would seem that the AC being charged DID have an effect on things, as looking at the wiring diagram, the AC pressure switch is connected to the thermoswitch circuit.
My current opinion is that either my new thermoswitch was bad from the start, my relay went bad somehow (maybe cuz I had it jumpered when the AC was fixed??), or I have issues in my wiring between the relay and the fans. Kinda seems like a relay issue at this point, but I'm really not sure about anything at this point. Heeeeeeeelp
1986 944na. LHD
Hit a raccoon about a week ago at around 60mph, hit the front right valence, busted foglight, and bent a couple of the brackets the valence bolts onto.
Get home and take off the valence, go to straighten one of the brackets in front, and accidentally puncture my condenser (not a good moment), emptying my ac system of the R-134.
Go to take it for a quick drive, as it still runs and drives fine, and upon idling up my driveway, I notice that my temp is creeping up and up, and no fans coming on (they had been working perfectly prior to the raccoon run-in)
Well ****. After performing Clark's test by jumping the pins on the plug that goes into the thermoswitch, all signs point to the thermoswitch being bad: relay passed with flying colors, turned the fans on and off as it should.
Replaced the thermoswitch the other day, and fans are still not coming on, even when idling up over the second white line on the temp gauge.
I know my fans physically work, I know my relay passed the Clarks test, although maybe it could still be bad (although that would seem unlikely to me), my coolant system is bled well with no air bubbles, and I have a new thermoswitch installed.
in my mind, it can't be a coincidence that my fans stopped right after hitting the raccoon, and emptying my AC system (oops). Given that none of the fan wiring runs on the right side of my car, I don't really see how the impact would have affected my fan's functionality. I also don't understand how emptying my AC system would have led to the fans not working, as it is a separate system. (fans do still turn on at low speed when I turn the AC on). Currently when cruising on the highway, in 85F temps, my temp stays right above the first line on the temp gauge, so stays in a normal range as long as I am moving.
I am beginning to think the thermoswitch I put in could maybe be bad, because if the clarks method of testing the plug by jumping it shows that everything down the line from the thermoswitch is doing its job, that would point back to the thermoswitch being the issue. I am having my ac serviced this Thursday, but I don't expect my fans to come back on when my AC is fixed.
Hopefully someone could shed some light on any ideas of what my issue may be, or have input for how to run tests to find whats wrong. Thanks
EDIT*****
Got my AC serviced, and back from the shop. I had the thermoswitch plug jumpered when I took it in to run the fans on high with the key on, and when I got the car back, and turned on the key, only the passenger side fan was on, and barely turning, so I quickly took out the jumper. When I turned on the AC, only the passenger fan ran. Got it home, and went to use clarks method to test the fans. Relay failed the part where you jumper the 2 and 3 plug spots, as instead of both fans coming on, only the passenger side came on. Relay passed the other tests. Fans still won't come on to cool the car even when idling up to the red. The weird part is, if I turn the car on and let it run, and turn the ac on, the passenger side fan runs, and the driver side fan comes on and off, on for maybe 10 seconds, and then off for 10. Is that normal fan operation for when the AC is on? I thought they were both supposed to turn on at the same time.
Overall, it would seem that the AC being charged DID have an effect on things, as looking at the wiring diagram, the AC pressure switch is connected to the thermoswitch circuit.
My current opinion is that either my new thermoswitch was bad from the start, my relay went bad somehow (maybe cuz I had it jumpered when the AC was fixed??), or I have issues in my wiring between the relay and the fans. Kinda seems like a relay issue at this point, but I'm really not sure about anything at this point. Heeeeeeeelp
07-31-2021, 05:31 PM
#2
Rennlist Member
The cooling fan relay isn't just a normal relay: it's got electronics in it. When they go bad from age, they can cause all manner of weirdness. I'd start diagnosis with a known-good relay. (It wouldn't hurt to have a spare as the cars age anyway, so even if it turns out to be something else you can put the spare fan relay in your glove box with your spare DME relay.)