1999 Chrysler Town and Country radiator fans won't run after lots of work?*&

ALDEN

MEMBER
1999 CHRYSLER TOWN AND COUNTRY
6 CYL
FWD
AUTOMATIC
160,000 MILES

I've replaced the fan relay, bolting it down where it goes, I've checked/replaced/wiggled the 40a fuse in the fuse box under the hood; I've wiggled the connectors on the fans. I've wiggled the connector from the fans that goes to a big clump of wires. I checked the power to the fan relay: of the 4 wires, one wire has power going to it and one is grounded (has continuity). I've hot wired the fans and they do run so the motors work. What's left? Is there another fuse or relay I'm missing?

Saturday, February 19th, 2011 AT 6:20 PM

7 Replies

CARADIODOC

MECHANIC
34,330 POSTS

Locate the two-wire coolant temperature sensor near the thermostat housing on the passenger side. Unplug that sensor while the engine is running. That should command the Engine Computer to turn on the radiator fan. If it does, the system is working.

Caradiodoc

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Saturday, February 19th, 2011 AT 6:37 PM

DOCFIXIT

MECHANIC
18,828 POSTS

Relay gounded by PCM to power fans possible fault with Coolant temp sensor see diagram

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Saturday, February 19th, 2011 AT 6:38 PM

ALDEN

MEMBER
4 POSTS

I have just replaced the coolant temp sensor. So when I unplugged it while running the engine like you suggested, the fans ran very weakly. I could feel the motors humming under my hand but one barely ran and the other not at all even though it hummed like a motor straining to work. Indeed they don't spin very freely when I just try to turn them. Sticky motors might be part of the problem. Before I just got code P1491. After I unplugged the coolant temp sensor I also get error code P0118. And I can't clear it even with the thing plugged back in. So now my radiator fans don't work and I have TWO engine codes. Now what? Thanks, A

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Saturday, February 19th, 2011 AT 8:50 PM

CARADIODOC

MECHANIC
34,330 POSTS

The coolant sensor code will erase automatically after 50 engine starts. That one normally does not turn the Check Engine light on after subsequent engine starts. You might have to cycle the ignition switch off and back on to turn the light off.

The humming / vibrating fan motor is a dandy observation. Some people actually complained they could hear the fan running when stopped in traffic. To address that concern, the engineers started using this "electronic fan relay" that you replaced already. It varies the duty cycle of the voltage that runs the fan motor to run it at the slowest speed possible that will still get the job done. "Duty cycle" means the voltage to the motor turns fully on and fully off many times per second. The percentage of on-time is varied to adjust the average voltage and speed. It's that rapid switching that makes the humming sensation.

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Saturday, February 19th, 2011 AT 9:06 PM

ALDEN

MEMBER
4 POSTS

So the fan motors are not faulty? Should they feel stiff/sticky or should they be very smooth/spin freely with the motor off?

Also my first question still stands - yes unplugging the coolant sensor made my fans start (sort of) but how do I FIX my problem? The fans don't run normally @#$% &*!
Thanks, A

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Saturday, February 19th, 2011 AT 9:15 PM

CARADIODOC

MECHANIC
34,330 POSTS

Sorry I wasn't more clear. Yes, the fans should spin very freely. When they don't, they draw excessive current and that's what led to the failure of the electronic relay and its fault code. You found the problem when you noticed how tight they are.

Caradiodoc

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Saturday, February 19th, 2011 AT 9:33 PM

ALDEN