2005 Chevy Silverado 5.3. Fan motors turn on mysteriously and with AC on the motor misfires


Asked by Aug 25, 2015 at 11:35 PM about the 2005 Chevrolet Silverado 1500 SS Ext. Cab Short Bed 2WD

Question type: Maintenance & Repair

I'm back to square one. My battery died and had a replacement installed. Next
day, with the AC on the motor began to mis-fire.  Fuel smell was all in the
truck. Took it to my mechanic who ordered a tune up, replaced all plugs and
wires. Mis-fire continued. Got the truck back and drove it for two days. Truck
would not start. The motor fans began to run in the middle of the night and
drain the battery. Back to the mechanic and a new computer was ordered,
flashed to my VIN and installed. Less than a week later, the truck is back to
same issues: mis fires with the AC on and fan motors are running without key
in the ignition. Is is a bad computer part?  Ignition? Something else?

2 Answers


This is just a guess but I'm thinking bad engine ground. The fans, a/c compressor, and ignition system all need good engine grounds to work correctly. When you have a bad ground sometimes current will "leak" through other circuits to find a ground. Also, both the a/c compressor and the cooling fans run when the circuit is completed to ground. Either by you pressing the button on the dash (a/c) or by the PCM. HTH. -Jim

Tom Harmon

What did he find on the first repair? Change a computer is almost insane ... since the introduction of Boeing's 777 there is not one mechanical linkage from the pilot to the control surfaces. The plane is "Fly by wire" .. my point is that over 500 people's lives are dependant on that computer not failing. To have 1 fail in a car is very,very unusual but to have 2 fail with exactly the same failure is unbelievable. First thing you have to do is find a mechanic instead of a "Parts Changer"

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