Radiator fan not working

Tiny
FLARON
  • MEMBER
  • 2012 FIAT 500
  • 1.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 93,000 MILES
I replaced radiator. Fan system and thermostat unit. Fan does not kick on either low or high. I checked relays and fuses and all good. Ran wire directly to fan from battery and it turned on. Checked voltage at relay and fuse panel all good. Check fan resistor soldering since it's new built in and all good and got resistance. Checked voltage where fan plugs in and no voltage but think voltage only occurs when fan is needed. Temperature gauge rises to halfway mark. I ran engine without cap in case of air locks. What is causing it not to kick on?
Friday, May 14th, 2021 AT 12:33 PM

1 Reply

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
We need to backtrack a little and find out how you checked the relay. You have two relays one for all speeds but high. Then you have a relay just for high.

We need to find out what the voltage is at each of the numbered places.

https://www.2carpros.com/articles/how-to-check-wiring

Starting with number 1. You can either check it at the PCM or at the PDC, where ever is easier. However, you need to check for ground and not voltage.

The PCM grounds this circuit to close the relay as power is supplied from the BUS bar in the PDC. So if power is supplied then it needs a path to ground.

So you need to check this by putting your red meter lead on battery positive and then the black lead on this circuit. Then run the engine until it is warm and your meter should read 12 volt when the fan should be on.

If it does then move onto number 2. This is the fuse that should have power on both sides of the fuse at all times.

Lastly is number 3. If the fuse is working, and the PCM is grounding the control circuit, and the relay is working then you will have voltage here. We can assume you don't since you checked it at the fan already and it is not there. So that means we have an issue with the PCM, fuse, or relay.

Please let me know what questions you have. Thanks
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Sunday, May 16th, 2021 AT 6:37 AM

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