1999 Pontiac Bonneville Electirc Fans INOP

COMPG

MEMBER
1999 PONTIAC BONNEVILLE
6 CYL
FWD
AUTOMATIC
161,000 MILES

Just dropped a new motor in this 99 from a 95. Switched all the motor electronics. Kept same fans in the 99. Dont know if they worked b4 the swap. Didnt unplug any of the wiring. Do they run on relays? There appears to be a module on the left fan and they are wired in series. Do these commonly go bad? Wiring is my low point dont even know where to start.

2 Replies

JACOBANDNICKOLAS

MECHANIC
108,310 POSTS

The fans are actuated by a temp switch that tells the computer that engine temp. From there, power is sent to a relay which turns the fans on.

The first thing I would recommend trying is to rin a wire directly from the battery to the fans to see if they will work. If they do, then we know the motors are good. Also, check in the power distribution box for the fan relay. See if there is another relay with the same part number and switch them to see if the fans turn on then. If they do, the get a new relay. If they still don't work and you know the motors are good, then move to the temp switch (near thermostat housing). Check for damaged wires, corroded connector. If all is good, replace the switch.

Let me know what you find.
Joe

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Wednesday, December 16th, 2009 AT 8:25 AM

COMPG

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3 POSTS

Ok I jumped the relay sockets and got the fans to kick on. High and low. I benchtested the relays and got them to click. The fans come on when the defrost or ac comes on. At the temp sensor in intake there is power and ground, and the correct 5 volt on the pcm wire. Fuses are all good. I havent tested resistance in the sensor from cold and hot temps yet struggling for time. But the temp sensor I bought new when I swapped the motor. Not much to a temp sensor really. If I test it and its good then what is the only poss? The wire from pcm to relays or fuses (not sure which is first) is bad right? Is there two wires from pcm one for high and low?

I've ran it to operating temp and above a few times to make sure the cooling system was full. Both times I did I ran it to prob 250 range, fans never came on. Unplug the temp sensor they kick right on. Fig thats a safety that if ur pcm isnt getting a signal it kicks the fans on high automatically. If thats the case then I would assume the pcm wire to relays would be good?

Btw thank u very much for ur time and assistance on this. I really app. Jus cannot afford to take it somewhere right now at all.

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Thursday, December 17th, 2009 AT 11:41 PM