Cooling fan not working
Thread Starter
Racer
Joined: Sep 2022
Posts: 338
Likes: 67
From: Escondido, CA
Cooling fan not working
My main cooling fan is not running but the aux fan is. I removed the relay next to the fan, applied power to the red/black wite and the aux fan runs only. Is there a different location to test-run the main fan? I’ve already confirmed the fuse is good.
Instructor
Joined: Jul 2020
Posts: 227
Likes: 43
From: New Jersey
Are you using the A/C or the defroster? On my son's 1990, I believe the ECM will turn the aux fan will on whenever the A/C pressure on the high side is above 190psi. Perhaps this could be sufficient airflow that the ECM never needs to turn the primary fan on? I think if you jump A&B terminals in the ALDL connector it will turn on all ECM-controlled accessories - including both fans.
Thread Starter
Racer
Joined: Sep 2022
Posts: 338
Likes: 67
From: Escondido, CA
Thanks, I’ll try that. I found the main fan wasn’t running because the car was heating well over 250F and when I popped the hood the main fan wasn’t turning. Once it cooled down, the next day, I did this test.
Thread Starter
Racer
Joined: Sep 2022
Posts: 338
Likes: 67
From: Escondido, CA
So I put it into Diagnostic mode and the main fan runs. I start it up and the temperature usage on the dash climbs fast. The aux fan doesn’t go on until it hits 260. Pretty soon it’s at 299! But I can touch the valve covers. It just doesn’t feel like it’s even up to temp. This is all in the span of about 10 minutes. Putting an oven temperature probe on the intake manifold measures 150. And the Low Coolant guage is on.
Ya know, I made an error where I got oil into the coolant. I’ve since cleaned it out but It’s wonder if the sensors are somehow spoiled?
Ya know, I made an error where I got oil into the coolant. I’ve since cleaned it out but It’s wonder if the sensors are somehow spoiled?
Last edited by Shunyun; Jul 14, 2023 at 09:59 PM.
Intermediate
Joined: Mar 2024
Posts: 44
Likes: 2
From: Indiana
welcome the the world of c4's...these cars run hotter than other cars that you are used to. The main fan does not turn on until the car reaches around 220 r so the the aux fan will kick on around 230...on a hot day cruising in town expect the temp to be high...if it get around 220 or more and the fan has not kicked on just get out on the open road and the natural air circulation will cool it down.
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