Cooling Fan Problem
Thread Starter
Intermediate
Joined: Apr 2009
Posts: 48
Likes: 0
From: Lincoln Nebraska
Cooling Fan Problem
I am struggling to get the cooling fan in my 85 to function properly. Neither of the fans are turning on causing the car to overheat. At first I assumed that the problem was my cooling fan switch, so i replaced that with a new unit that turned the fans on at around 209. This fixed the problem for a short while, but again neither of the fans are turning on at any temp.
I replaced the switch again with no positive results. I have been running the fans all the time by grounding the wire that leads to the switch. I have tested the switches, the wiring and the connectors around the switch and they all seem to be fine.
Any ideas as to what the problem could be? Could this be an ecm or a relay problem?
I replaced the switch again with no positive results. I have been running the fans all the time by grounding the wire that leads to the switch. I have tested the switches, the wiring and the connectors around the switch and they all seem to be fine.
Any ideas as to what the problem could be? Could this be an ecm or a relay problem?
Le Mans Master
Joined: Jul 2007
Posts: 5,356
Likes: 2
From: No HOA, New Hampshire
Cruise-In X Veteran
St. Jude Donor '09
I am struggling to get the cooling fan in my 85 to function properly. Neither of the fans are turning on causing the car to overheat. At first I assumed that the problem was my cooling fan switch, so i replaced that with a new unit that turned the fans on at around 209. This fixed the problem for a short while, but again neither of the fans are turning on at any temp.
I replaced the switch again with no positive results. I have been running the fans all the time by grounding the wire that leads to the switch. I have tested the switches, the wiring and the connectors around the switch and they all seem to be fine.
Any ideas as to what the problem could be? Could this be an ecm or a relay problem?
I replaced the switch again with no positive results. I have been running the fans all the time by grounding the wire that leads to the switch. I have tested the switches, the wiring and the connectors around the switch and they all seem to be fine.
Any ideas as to what the problem could be? Could this be an ecm or a relay problem?
If that doesn't help, check the wiring backwards to the ECM.
Thread Starter
Intermediate
Joined: Apr 2009
Posts: 48
Likes: 0
From: Lincoln Nebraska
I have a new relay on the way to try. I don't understand wiring very well, could the problem be the relay or the computer even though the fan works fine when the switch wire is grounded?
This may be a stupid question but what exactly does the relay do?
This may be a stupid question but what exactly does the relay do?
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The relay supplies 12v to the fan motor when it is turned on. The ECM turns on the fan relay from info supplied by a temperature sensor. You can test the relay and fan motor by grounding the green/wh wire on the fan relay with the ign sw in run. The relay should close and the fan should run. You can hear the relay click when it closes and you can use a voltmeter to see if 12v is at the fan motor. You can also check the fan motor by unplugging it and connecting 12v to the fan motor wires. Fan motors don't last forever, they have brushes that wear out. It is a lot cheaper to test the circuit than to just start replacing parts!!!!!! More intelligent too.
