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sprinkles08
sprinkles08, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 21570
Experience:  ASE Master & Advanced level certified, Chrysler Master Certified, Trans and Hybrid Specialist
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Cooling fan not working on PT Cruiser

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01 Pt Cruiser non turbo, AT. 126,000 miles, in great shape. High temp gauge reading yesterday lead to discover that the cooling fan was not coming on. Thinking this would be cut & dry I opened the PDC cover, & removed the fan relays. Put B+ straight to pin 87 in low speed relay socket = no cooling fan. Put straight B+ to pin 87 in high speed fan relay socket = cooling fan spins, I would not say at a high speed, but it came on. Checked continuity & power supply to connector, was as it should be. Both relays test good. Have I reasonably diagnosed this to just the cooling fan, or do I also need to look at the coolant temp sensor, or consider the PCM?... I didn't understand why the fan only came on for the high speed side.... thanks in advance.

Hello and welcome to JustAnswer!

 

If the temperature gauge works ok then you can rule out any problem with the coolant sensor.

 

The PCM could be a possible cause of the fan not coming on if it had a failed relay driver and couldn't turn the relay on, but that probably isn't your case. It's not common or likely, and in your case if there was a problem with the PCM that would mean you have more than one problem going on at the same time.

 

If the fan won't come on low speed when you power it from the relay then either the wire from the relay to the fan is broken or the fan motor is bad. Wiring problems are possible, but it's very likely that the low speed circuit in the fan motor is bad. This isn't an unheard of problem on the PT. Since the fan seems to run slow on high speed that's another sign that the motor has failed.

Customer: replied 5 years ago.
Thanks. I agree, & with no codes, well only a P1684 code displaying, (???), the PCM is seemingly ruled out also. And I guess that ultimately becomes my question. You are saying that there are two circuits in the fan motor, not just a single circuit with a transformer or a resistor to change rpm?.. that would be great to know & conclusive in my efforts. Obviously I'm asking as I don't have it out yet.. thanks. I'll try not to bother you further.

P1684 sets when the battery has been disconnected.

 

If there are no other codes then the wiring from the PCM to the relays is fine. The PCM itself is also very likely ok.

 

There are two circuits in the motor, hence two relays, two wires, and a three wire electrical connector on the fan motor. One wire is ground, the other two circuits come from the high and low speed relays and utilize separate circuits and brushes in the motor to give you the two separate speeds.

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Customer: replied 5 years ago.
Sweet, thanks for the confirmation. Take care.

You're welcome, and good luck with it!

 

 

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