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Ron, ASE Certified Technician
Category: Chevy
Satisfied Customers: 35485
Experience:  35 years experience with ASE Certs
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How to trouble shoot radiator fan not coming on when hot.

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How to trouble shoot radiator fan not coming on when hot. I've checked fan direct with 12 volts and fan runs. I've also checked with ac on and does not come on when engine is running too. Need to know how to check other sensors.

Hello. My name is ***** ***** I am happy to assist you today. Give me just a moment to review your post, and I'll be right back with the help you need.


Have you scanned the computer system to see what the fault code and or codes are that should be setting?

Customer: replied 9 months ago.
No I haven't

Okay I am sending you the steps to pinpoint the cooling fan and the system. See the steps in the link below. Have a look and post back if you have more questions and or need more help and we can work from there.

See the wiring diagram in the link below as well for testing reference.

Customer: replied 9 months ago.
Okay, so the fan module died again. I replaced it and it's only been 3 days. What else could be causing this?
Customer: replied 9 months ago.
When I first tested the fan while still mounted on car it didn't work but when I took fan shroud off car tested it it worked. So I assumed it was good. So I changed fan module. Changed fan module and it worked. Ac on fan worked fan worked fine no overheating. Now fan stoped working again car runs a little hot.

Are you getting proper and ground to the module?

Customer: replied 9 months ago.
How do I check for ground on the module?The module is mounted on a plastic shroud so if there's a ground it's in the wire harness. I took the fan off again today and tested fan and fan runs ok. Check wiring conecters it's plugged in good. Your wiring diagram did not come thru couldn't get it up. I had a reading on the check engine light P0691. Help I'm stumped.

The cooling fan system gets its ground from the G105 located at the left front of the engine block. See the location in the link below, its #4 in the diagram.

Customer: replied 9 months ago.
Is there anyway to check the fan module? Omh meter for resistance?I kept my old one and I can test it against the one I replaced if there's a way to check the fan module. Send picture and diagrams if possible. So if I have good ground then what? I mention that the read out was P0691.

Are you sure the 60 AMP fuse for the cooling fan is not blown. Its located at position 1 in the under hood fuse block. Did you check it?

Customer: replied 9 months ago.
The cooling fan fuse is a 40amp its good . When I check the p0691 code it keep referring to a relay but there is no relay for the cooling fan circuit. I'll check the 60amp fuse too. There's only one 60amp fuse in the box.

Okay , I have also enclosed test step for the code P0691 in the link below.

Customer: replied 9 months ago.
Thanks Ron I'll work on it and let you know what happens. Will get back to you.

Okay , Im here most day if you need me.

Ron and other Chevy Specialists are ready to help you
Customer: replied 9 months ago.
Ok Ron I'm stumped. Is it possible the fan control module the new one I bought went bad too? When I installed it everything was good for 2 days then the fan went out again. I've check everything that I could. I don't think it's possible there's a short if so it should cut the fuse first. It's kind of costly to purchase another module just to try to find out if that's not the problem. Anymore suggestions.

It could very likely be defective if it worked okay for two days. If the testing looks okay that may be the case. If the module only lasted two day I would see if they will replace it under warranty.