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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29519
Experience:  GM Grand Master Technician 2007. 14 years experience.
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The fan comes on all the time even if its not hot, changed

Customer Question

The fan comes on all the time even if its not hot
JA: What is the model/year of your Chevy?
Customer: changed the ETS and therm
JA: What year is your Chevy?
Customer: 2008 trail blazer 4x4 4.2l vortec
JA: Are you fixing your Blazer yourself? What have you tried so far?
Customer: yes doing the work myself
JA: Anything else you want the mechanic to know before I connect you?
Customer: yes lights dim when pulling the window buttons up
JA: Just to clarify, what are the exact lights you're talking about?
Customer: in the vech and headlights
Submitted: 9 months ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 9 months ago.

Hi there, I am Cam. So the engine fan comes on at times when it should not, am I understanding that correctly?

Customer: replied 9 months ago.
no the fan comes on all the time. lights dim head lights and inside lights when i pull the windows buttons up.
Expert:  GM Tech (Cam) replied 9 months ago.

OK, Which fan, the fan inside the vehicle or the engine fan?
And the lights, that happens when you add the load of the power windows?

Customer: replied 9 months ago.
The engine fan
Expert:  GM Tech (Cam) replied 9 months ago.

Ok, Does the dash show the check engine light as well?

Customer: replied 9 months ago.
Customer: replied 9 months ago.
are you still there ? had a internet problem
Expert:  GM Tech (Cam) replied 9 months ago.

Ok so its likely that your fan clutch has failed or the relay that controls the fan has failed. There is a device much like a relay and that looks similar to a relay for the engine fan in the under hood fuse. This is common for failing. There is another one for the Low beam headlights. Swap these to see if the fan acts normally or if the low beams go out. If so then the relay is bad. . The numbers on the top are 15016745. That is also the part number to order if that if the lights come on.

If that does not correct, then you likely have a bad fan clutch. This electrical load could be made worse by using the windows and such resulting in your other issue.

Customer: replied 9 months ago.
ok, going to check what you said out. thank you very much,have a blessed night
Expert:  GM Tech (Cam) replied 9 months ago.

You are most welcome.

Customer: replied 9 months ago.
took the relay fuse out the light turned off .
Expert:  GM Tech (Cam) replied 9 months ago.

Ok but did you swap the 2 relays to see if the issue remained the same?

Customer: replied 9 months ago.
i took the relay out the 15016745 and the headlights went out fan still running the low beam fuse was a 10 fuse,couldnt switch them. the relay fan fuse was listed as HDM # 46 on fuse box?
Customer: replied 9 months ago.
still where we started... any more ideas?
Expert:  GM Tech (Cam) replied 9 months ago.

Ok if you removed the fan relay and it stayed running then it confirms your fan clutch has failed.

And sorry for the delay, I am also a paramedic and I got busy.