Cooling fan problems
Thread Starter
Cruising
Joined: Feb 2008
Posts: 12
Likes: 0
Cooling fan problems
Hi everybody, I'm having a problem with the cooling fan on my 85, I just have a single fan and as soon as I turn the key to start the car the cooling fan comes on? I have replaced the relay, checked the wires, coolant sensor works, the only thing I can think of is the ECM is bad? Does anybody have any other ideas? Thank you very much.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
As I recall the '85 was a one year only setup;
ECM control from the CTS with temp switch BACKUP.
In '86- '89, the temp switch controls the 2nd fan if fitted
Poss the switch is faulty; permanantly grounded so fan is on full time.Disconnect the temp switch ( not the CTS ) and see if fan still runs.
Or A/c pressure switch
Process of elimination.
ECM control from the CTS with temp switch BACKUP.
In '86- '89, the temp switch controls the 2nd fan if fitted
Poss the switch is faulty; permanantly grounded so fan is on full time.Disconnect the temp switch ( not the CTS ) and see if fan still runs.
Or A/c pressure switch
Process of elimination.
Last edited by rodj; Feb 19, 2009 at 06:19 AM.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
With a single fan setup only the ECM turns on the fan. It's possible that someone has wired it differently so that a temp. switch (in the head, probably) would be used Instead, or in parallel, and that switch would be suspect.
(Without looking back at my FSM I don't Think that a switch in the head was present in '85 with only a single fan setup.. I Could be wrong.)
The fan Could have been hot wired to stay on all the time.
Or the Relay is stuck closed.
Otherwise it's an ECM or ECM Input problem. You'll need a scan tool to look at the inputs - Coolant temp. and A/C pressure - to see if the ECM is doing what it should, or if it is turning the fan on improperly..
(Without looking back at my FSM I don't Think that a switch in the head was present in '85 with only a single fan setup.. I Could be wrong.)
The fan Could have been hot wired to stay on all the time.
Or the Relay is stuck closed.
Otherwise it's an ECM or ECM Input problem. You'll need a scan tool to look at the inputs - Coolant temp. and A/C pressure - to see if the ECM is doing what it should, or if it is turning the fan on improperly..
