HELP. 86 LG4 overheating, erratic fan operation` - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 3 (permalink) Old Jun 9th, 99, 05:39 PM Thread Starter
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Join Date: Mar 1999
Location: College Park, MD USA
Posts: 42
I need help troubleshooting the cooling system on an 86 IROC with an LG4 V8. The engine is overheating and I've determined that it's because the cooling fan isn't functioning properly. It's an electric fan, and obviously controlled by some kind of relay or sensor that tells it when to turn on/off. The problem is that it functions sometimes, and other times it doesn't turn on at all. I've tried "jiggling" the wire running to the fan, and that seems to have no effect.

I need to know what electric/mechanical/electronic system controls the operation of this fan. Is the cooling fan controlled by the ECM and the associated coolant temperature sensor? Does it operate on some kind of relay attached to the sending switch? Is it the same sensor that controls the temperature gauge (which is functioning normally)?

Please, if anyone can help me determine how this unnecessarily complex system works, or what in the system may be causing my fan to malfunction, I would appreciate it. This car's my daily driver and I need it working ASAP.

I suppose if worse comes to worst I could short the switch and have the fan run ALL the time, or run to the box and put a hand-switch in the cabin for manual shutoff when warming up, but I'd much rather avoid the trouble and correct the problem properly.

Thanks in advance.

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post #2 of 3 (permalink) Old Jun 17th, 99, 05:58 PM
Join Date: Jun 1999
Location: ST.LOUIS MO. USA
Posts: 1
Your fan is controlled by the ECM. It works off a coolant sensor . It should turn on around 228 degrees and back off at around 214 degrees. It also comes on when the A/C is turned on from a high pressure switch. These both go through a relay mounted either on the front passenger side of the core support or on the right side fender, towards the front.The fan does not run all the time.I beleive it stays off above 30mph unless you have an overheat condition.What exactly is the system doing? Also check to make sure the undercar airdam is in place. If it is missing it will cause your car to over heat. It is not controlled by the same sender for the gauge.This senor is in the intake [front]Should be a yellow wire and black wire.

[This message has been edited by DAV43 (edited 06-17-99).]
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post #3 of 3 (permalink) Old Jun 25th, 99, 04:51 PM Thread Starter
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Join Date: Mar 1999
Location: College Park, MD USA
Posts: 42
Thanks, I appreciate the help...but as it turns out, I had a bad fan motor. I replaced it and it works least it DID work fine until my water pump started leaking.

Seems like with this car the challenge is to repair one problem in time to deal with the next when it pops up. Oh well...water pump isn't too hard, is it?

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