Overheat due to fan not working - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 8 (permalink) Old Oct 5th, 01, 08:01 PM Thread Starter
 
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Location: Melbourne, FL, USA
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I have a Camaro 95 V6 3.4L.
I have one Fan only and it doesn't work when the engine overheats and it will only come on when you turn the A/C on.
After troubleshooting I found the following:
1- there is nothing wrong with the fan because it works when I turn the A/c on.
2- there nothing wrong with the relay because as I said the fan comes on when I turn the A/C and I even changed the relay with a different on but still nothing.
3- I replaced the ECT (coolant temperature) sensor, even though the old one was ok.
4- I checked the temperature gage and it works even it is irrelevant.
5- the wire from the PCM to the ECT sensor is ok because I can measure +5V on the two terminals of the wire when I disconnect it from the ECT sensor
6- the wire from the PCM to the fan is ok because the fan turns on when the A/C is on and even if I disconnect the PCM wire from the ECT the fan will come on, but once I connect it back to the ECT the fan will turn off.

I ran out of ideas and I am about to go to the dealer, which I heat to do so.

Please advise.

Thanks
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post #2 of 8 (permalink) Old Oct 5th, 01, 08:09 PM
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Don
 
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Location: Houston, Texas
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Quote:

5- the wire from the PCM to the ECT sensor is ok because I can measure +5V on the two terminals of the wire when I disconnect it from the ECT sensor

Voltage should be present on the yellow wire only. Possible bad PCM.
Also you may want to check all PCM grounds.

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Don~ ZZ430DropTop
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[This message has been edited by ZZ430DropTop67RS (edited 10-05-2001).]
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post #3 of 8 (permalink) Old Oct 5th, 01, 10:49 PM Thread Starter
 
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yes i measure +5V on the yellow wire only.
The PCM controls the coolant fan relay, and there us an A/C request the PCM turns the fan on through the relay.
and as I said if i dissconnect the yellow/blak wire from the ECT the fan will turn on but the car will function in strage way.
but it might be a bad PCM.
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post #4 of 8 (permalink) Old Oct 15th, 01, 10:52 AM
 
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Location: Tampa, FL USA
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You should have a temperature controlled fan switch somewhere, I know on the 305 it is on the passenger side under the exhaust manifold. If the fan comes on with the AC it probably means that the switch is out. To test it unplug the lead going into the switch and ground the lead (not the switch)on something. If the fan comes on replace the switch. If not it is something I am not familliar with. Mine did this after I bought it. It drove me crazy, it overheated without the AC on but ran cool with it. Finally figured it out. For more tips you can check www.thirdgen.org. Lots of good stuff there.
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post #5 of 8 (permalink) Old Oct 16th, 01, 07:05 AM
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Dave
 
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The cooling fan is controlled by the PCM in your vehicle. There is no fan switch. It is possible that your ECT is sending the PCM an incorrect reading, but that is unlikely since you already replaced it. The cooling fan control circuit is a Dark Green wire that runs from the cooling fan relay to an inline harness connector pin J and then to the PCM at terminal B2. If you check the continuity of this wire and it is ok, then I would bet that the PCM is the problem.
Dave
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post #6 of 8 (permalink) Old Oct 25th, 01, 10:53 AM
 
Join Date: Jun 2001
Location: aiken,south carolina, us
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Hey I have a 88 iroc camaro that neither of the fans would come on unless you turn on the Air Conditioner and then it would just stay on for a couple of seconds. I just wired the ground wires coming from the fans to a ground on the car. Now the fans stay on all the time but the car has never been over 150 degrees now. I hope this helps.

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michael gunnells
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post #7 of 8 (permalink) Old Oct 25th, 01, 08:36 PM
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When you say the car is over heating do you mean the gauge is pegged or coolant is pushing out?Some cars now-a-days don't turn on the fans until the coolant temp is 220* or like you notice when you turn the airconditioning on.Most cars today use a thermostat rated at 195*. That is the temp it 'starts' to open.It might be 210 or so before it 'fully' opens.So please clarify what you mean by overheating.Michael with the 88 iroc you are not doing your cylinder walls any favors by running your engine so cold.The fuel is not being fully vaporized and is 'washing' the oil off your cylinders causing wear.Gm wired those fans a certain way for a reason.
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post #8 of 8 (permalink) Old Oct 26th, 01, 12:43 PM Thread Starter
 
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Thanks,
I found that the fan turns on when the Temp. is 224 and it truns off when it reaches 212.

once again thanks to you all.
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