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Ask Michael Moore Your Own Question
Michael Moore
Category: Chevy
Satisfied Customers: 2956
Experience:  ASE Master/GM WORLD CLASS/GM Master/GM ASEP/Dodge Gold/Mazda cert.
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the fan on my trailblazer is running high all the time.

Customer Question

the fan on my trailblazer is running high all the time.
Submitted: 7 years ago.
Category: Chevy
Expert:  Michael Moore replied 7 years ago.

Which fan is running, the a/c fan or the cooling fan for the radiator?


Does the truck have auto hvac controls with a digital display?

Customer: replied 7 years ago.
It's the radiator cooling fan. Yes there are HVAC digital controls. The fan thing started suddenly. It is still occuring after the truck sat for several hours.
Customer: replied 7 years ago.
Radiator cooling fan is running fast at all temps. Just started suddenly. still continuing after severeal hours cool off. Ambient temp is between 30 and 50 degrees farenheit.
Expert:  Michael Moore replied 7 years ago.

Are you sure its the radiator cooling fan? This truck should have a fan that is driven by the engine belt.


Is it a trailblazer or a blazer?

Customer: replied 7 years ago.
It is a 2002 trailblazer. It is the fan that is attached to the shaft coming from the water pump. The large white plastic fan that is about 16 to 18 inches in diameter. The fan that sits right behind the radiator and helps to cool the engine.
Expert:  Michael Moore replied 7 years ago.
Sorry, I think i miss read The fan does not run with the engine off! I thinking that the fan stays on, but you are having a issue with the cooling fan staying engaged all the time. The problem is the cooling fan clutch, this is common for these trucks and the only repair is to replace the fan clutch. The fan clutch is controlled by the engine computer and a relay, you can try switching the relay with the HDM relay. They are both located next to each other in the under hood fuse box, the HDM relay and the cooling fan relay are differant then all the other relays and can not interchange with them. The HDM relay controls your headlamps, so if they stop working after replacing the relay, then that relay is bad.