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Old 10-25-2013, 11:31 AM   #1
Reddawg67
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Question Cooling fan runs all the time

Hi I'm new here & also to posting. I have a 93 pontiac grand am 3300 V6 with auto tranny. My problem is cooling fan starts running as soon as car is started. AC not on or defrost. In turn doesn't allow engine to reach normal operating temp. I have replaced both the ect sensor & gauge sending unit. I've noticed there's a red light with temp symbol in lower left hand corner of instrument panel that stays on & won't allow ac to come on. Also if I unplug fan relay & allow engine to come up to operating temp the light hoes off. Until the engine drops below 200degrees then it'll come on again. It has just the one fan & I have ruled out the fan relay cause I replaced with a new one. Also if anyone has access to wiring diagram for the rest of relays on firewall & as to what they control would be greatly appreciated as well. Thanks for your time & any thoughts as to what the next step would be.
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Old 10-25-2013, 07:31 PM   #2
Tech II
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Re: Cooling fan runs all the time

Have you checked for codes? there are some codes that will cause the cooling fan to run constantly when a code is set....

The fact that your temp light is on, is another reason the fan is running......

Have you replaced both coolant temp sensors? One is for the ECM(computer), the other for the temp gauge in the cluster....

From the diagram, you can see that the fan control relay is controlled by the computer, ECM....
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Old 10-25-2013, 09:12 PM   #3
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Re: Cooling fan runs all the time

Yes I've checked for codes & all there is 12 which I believe is for battery. Correct me if I'm wrong. I did however find out what the red warning light was for & in the process of checking wires to see if there's a short or anything of the sort. I've gotten a better diagram than what was in my Haynes manual. Still running wires & testing so hopefully tomorrow I can find out what's causing this problem. It's my uncles car & supposedly been doing this for quite sometime so I'm wondering if computer is part of problem also & if any wires are shorted. Thanks for the info & diagram. All help is greatly appreciated. Will start again in the morning & see what I find & will let you know.
Thanks again!
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Old 10-25-2013, 09:17 PM   #4
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Re: Cooling fan runs all the time

By the way I have replaced both the ect sensor & temperature sending unit for gauge. Thanks for all input Tech II!
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Old 10-26-2013, 07:33 AM   #5
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Re: Cooling fan runs all the time

The way these sensors work, is by resistance, high resistance should produce low temp readings by the ECM....low resistance, creates high temp readings.....

So if you have a short in the circuit to the sensor, this makes the ECM think you are overheating, and would cause the fan to run constantly......

But the only true way to diagnose this is with a scan tool.....you can go to a place like Autozone, and they can hook up their scan tool, and read the coolant data.....if it is reading very high, even though it's not, then you would have to check the circuit between the sensor and the ECM for a short...if it is ok, then you need an ECM...

code "12" has nothing to do with the battery....it means that the diagnostics of the ECM are working properly....When the red temp light is on, what is the temp gage reading in the dash? This should be compared to the coolant temp reading of the ECM.....

Surprised a code "14" is not set....which could mean an ECM problem.....
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Old 10-27-2013, 04:50 AM   #6
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Re: Cooling fan runs all the time

Tech II I found why all this was happening. Pulled fuse cover & the ERLS fuse had been hot & melted area around the fuse & wires coming out of this circuit had the insulation melted. You could just imagine the damage & I'm surprised it hadn't caused the car to catch fire. It's a 10 amp circuit & there was a 15 amp fuse in it. Long story short, I've traced & in process of replacing wires & damaged connectors just hope it hasn't damaged any circuits in ECM. I really appreciate all your input & I'll post back after all repairs to let you know it's all working properly. Thanks again I really appreciate people such as you with reliable information to help someone in need. Which in my case was car owner negligence to replace with proper fuse & also have problem diagnosed properly to start with. Hope you have a great day!
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Old 11-19-2013, 05:13 PM   #7
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Re: Cooling fan runs all the time

fuses and relays, first things to check besides for trouble codes.
good call Tech II
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