Radiator Fan not working
Thread Starter
Racer
Joined: Feb 2009
Posts: 492
Likes: 19
Radiator Fan not working
1992 LT1, “secondary”/passenger side fan not coming in when temps reach 238. Driver side/ primary fan comes on at temp and when the A/C is triggered but the other doesn’t. The only way I can get it to work is by pinning A/B on the diagnostic port, then both fans work correctly. What should I look into next? I’ve also already swapped relays that attached to the fan shroud with no change. However like I said when triggered both fans come on so I’m assuming wiring and relays should be good throughout.
Advanced
Joined: Dec 2020
Posts: 84
Likes: 16
1987 Chevy Corvette
1992 LT1, “secondary”/passenger side fan not coming in when temps reach 238. Driver side/ primary fan comes on at temp and when the A/C is triggered but the other doesn’t. The only way I can get it to work is by pinning A/B on the diagnostic port, then both fans work correctly. What should I look into next? I’ve also already swapped relays that attached to the fan shroud with no change. However like I said when triggered both fans come on so I’m assuming wiring and relays should be good throughout.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Considering with what the information you provided the wiring, relays, power to the relays both fan power and relay power is all there and working. The wire from the low side of the relay gets grounded thru the ECM. When you connect A & B and the passenger fan starts that means all wiring is good and the ECM is grounding the low side of the relay hence closing the relay.
But for some reason during normal operation the relay does not close which is a ECM function driven by the temp sensor in the water pump and also drives the temp digital display on the speedo. So it sounds the temp sensor is OK since it is displaying normal.
Getting to the bottom line it sounds like that function of the ECM is not working which starts the fan at 238 deg.
My only other question is will the driver's side fan come on at 219 deg without the AC being on. If it does, than that function is working normal. If it does not the it might be linked to the original problem.
This holds if the ECM is stock and set temps for the fan have not been changed. But I don’t know who would make them higher. (Nomake Wan has a point).
But for some reason during normal operation the relay does not close which is a ECM function driven by the temp sensor in the water pump and also drives the temp digital display on the speedo. So it sounds the temp sensor is OK since it is displaying normal.
Getting to the bottom line it sounds like that function of the ECM is not working which starts the fan at 238 deg.
My only other question is will the driver's side fan come on at 219 deg without the AC being on. If it does, than that function is working normal. If it does not the it might be linked to the original problem.
This holds if the ECM is stock and set temps for the fan have not been changed. But I don’t know who would make them higher. (Nomake Wan has a point).
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Pop the MEMCAL cover off the ECM and inspect the MEMCAL itself, just to be sure. As the other user said I'm not sure why someone would screw up the fan activation points, but that's the only thing I can think of as being a cause if everything else in the system is working properly.
