coolant fans on 98 monte carlo - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-07-2016, 07:05 PM   #1
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Default coolant fans on 98 monte carlo

hi, on my 98 Monte carol with a 3.1 eng and the car wont turn the fans on low or high. i can turn the fans on with a scan tool or if i ground the coil side of the relay at the ecm. i pulled the harness apart and did a ohms test on the circuit one wire at a time all at .02 ohms per wire. i try to ground the black and yellow wire lead at the temp sensor and the fans did not come on.with the fans on the blow wire which is the frist wire i get battery voltage then after it goes thought the fan motor voltage dropes to 6.75 and by the time voltage goes thought fan number two it drops to less then a volt. out of opinion any one get any thoughs thank you
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Old 01-08-2016, 05:48 AM   #2
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Start the engine, disconnect the coolant temp sensor. What happens?
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Old 01-08-2016, 10:27 AM   #3
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if you can turn the fans on with a scan tool, or by grounding the relay, there is nothing wrong with the fans or relay.....either a PCM problem or sensor problem....scanned for codes?

Since you have a scan tool, what are the coolant sensor readings?

The voltage readings you are getting are normal for low speed fans with each getting 1/2 Bat voltage......
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Old 01-09-2016, 10:12 AM   #4
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Default tech II

thanks for get back to me. To answer your question I unplugged the coolant temp sensor the reading on the scan tool goes to -38, jump the yellow and black wires it goes to 284 which i know it normal. Checked pcm drivers and find the scan tool saying hot lamp driver shorted, not sure if that is referring to the lamp on the dash or not. jumped fans to run and want for a drive. check eng light comes on, find code p0401a egr not sure what the A means. thanks for you help

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Old 01-09-2016, 10:58 AM   #5
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Forgot to ask you why you are worried about the fans not coming on, is the vehicle overheating?
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Old 01-09-2016, 11:29 AM   #6
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Quote:
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Forgot to ask you why you are worried about the fans not coming on, is the vehicle overheating?
Just like to have ever thing working as it should and it does run a little worm
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Old 01-09-2016, 01:31 PM   #7
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But at this time of year, those cooling fans may not come on......I'm guessing they wouldn't come on until at least 218F?

If you have a scan tool, start the vehicle and turn heater to full Cold, and blower off......

Watch the coolant temp as it rises.....fans should come on low speed, at least by 218-220F....
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Old 01-09-2016, 04:20 PM   #8
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Last I knew, they will come on at 212 and 226.
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Old 01-09-2016, 05:14 PM   #9
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Hard to keep up with the different engines, they seem to change the specs....mine was just a guess.....

I was just throwing a number out there...in the cold weather, those fans may not even come on...but they should be on by 220.....

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Old 01-09-2016, 05:20 PM   #10
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Hard to keep up with the different engines, they seem to change the specs....mine was just a guess.....

I was just throwing a number out there...in the cold weather, those fans may not even come on...but they should be on by 220.....
Nope run the temp up to 221 and still no fan I'm thinking it has something to do with the hot light drive in the pcm just not sure how to check it or which wire it is thanks
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