Fan Clutch Issues on 2004 Trailblazer

gdc4sman

New Member
My '04 TB LT fan started to intermittently fully engage at 97k miles causing the jet engine noise along with sluggish power (No engine codes). Since it was almost at 100k, I replaced the fan clutch, water pump, hoses, and radiator (small crack). The fan clutch was the Hayden 3200 model and new out of the box was worse than the OEM clutch I just replaced (Extremely loud jet engine noise). I returned it and replaced it with the DORMAN model and then had the dealer update the PCM firmware. Now I'm back to square one, as the clutch intermittently locks with the same issue and still no engine codes. From reading other forums, I'm guessing that the problem might be one of the sensors not working properly (Engine coolant temp sensor, transmission temp/manifold press sensor, or A/C pressure sensor).

My first inclination is to replace the Engine coolant temp sensor and thermostat even though the engine temp gauge shows a steady 210 degrees regardless of when the fan clutch is engaged or not. Any suggestions/recommendations would be greatly appreciated.
 

Mooseman

Moderator

KNBlazer

Well-Known Member
If possible, try sticking with AcDelco or GM parts....This platform seems to be extremely sensitive to aftermarket parts....some get lucky and don't have any issues with aftermarket...
 
OP
OP
G

gdc4sman

New Member
I temporally switched the headlight relay #46 with the fan relay #45 (same part number) and lo and behold the headlight auto-shutoff did not work - they stayed on when the keys were removed. This would be consistent with a bad relay causing the fan clutch to be engaged.

I'll follow-up after I get the AC Delco relay and test.
 

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