Radiator Fan Troubleshooting

[TomO]

I'm looking deeper into Nancy's radiator fan problems. She's an '04 3.7L with only the electric fan.

I see that there are two relays. One for high speed, the other for low. The problem is that coolant temp starts to rise when AC is on and speed is low. Idling in the barn with AC on, the fan did not run last night. I swapped each relay with the blower motor relay and confirmed that the blower motor does power up. I also confirmed that fuse #2 is still good ( it was blown the other day ). I did see the fan run that day, but I don't know which speed it was running at.

Are any of you familiar with the logic involved in this? What conditions must be met for the low speed vs. high speed operation?

Does the ECU provide a ground through something like an open collector output for each relay coil, or does it switch +12v to each relay?

I'm trying to find some good test points to try and determine when / if a run fan signal is being sent. Any help would be greatly appreciated.

 

[LibertyTC]

The cooling fan will be engaged when the ,air conditioning system is activated. Something is not right if the fan did not come on and AC on.....
The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F) The PCM stores any fault codes and is responsible for sensing.
IF you are not overheating & your temperature gauge is mainly in the middle area and the electric fan comes on when you engage AC you should be ok. (flush system every 5 years with new HOAT)
Keep the fan blades clean on electric fan units. Your system does not have any leaks I assume/it is pressurized properly...
I will try to find the schematic for fan/relays later....off to install PML ****** pan....

 

[TomO]

Thanks for that. I just confirmed that the fan does indeed run at low and high speed by jumpering across the NO relay contacts with the relays out.

I did not allow the coolant temp to get above 200 degrees F before panicking last night. I just don't like seeing the idiot gauge above 1/2 I guess. I'm reading coolant temp with my scan tool.

 

[TomO]

Some more troubleshooting and now I believe that the fan motor is at fault. I got the temp up over 200 degrees F and saw the motor running. It shut down around 210 degrees and then did not restart as the temp climbed again.

I could measure power at the connector but still no spin so I shut off the engine, pulled the relays again and this time I could not start the fan by jumpering across the relay contacts. I left the jumper in place and gave the fan a push and lo, it took off running.

Now to find a replacement.

 

[LibertyTC]

Sometimes it is just the brushes, but getting a new one long term is better.
Let us know what happens after new one is installed.

 

[TomO]

I played with it some more. I'm convinced it's a heat problem with the motor.

When it's cool, the motor runs fine. If I heat it up, nothing. I got it up to temp and ran power straight to the motor.

Where's a good place to get one? Autozone has one for $180, PartsTrain $140, Local Chrysler dealer $300. Those are for the whole fan assembly. I see a couple of motor only options, but no one can tell me if they're the 3-wire ( two speed ) or the one speed motor. I need the two speed.

 

[LibertyTC]

Personally the OEM Fan lasts a long time. You could try taking the fan motor apart and clean it up with WD-40, this may help.
The factory year specific OEM can be purchased for $217 http://www.oemworldparts.com/jeepparts/

 

[retmil46]

Try www.rockauto.com . Looks like they have a few choices - but again, you'll have to call and ask - no indication if they're one or two speed.

 

[TomO]

I have one on order from RockAuto. I chose the one with a picture of the same connector / 3-wire motor that I have.

About $65.00 after shipping.

 

[LibertyFever]

I had a similar problem with my Libby.

Don't go to a wrecking yard. I bought one from a wrecking yard for about $100 and wound up using two motors to make a single one.

I too recomend getting a new OEM fan.