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Stumped!!! Cooling Fan Won't Turn On!

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Old 03-08-2011, 06:09 PM
200Kclub 200Kclub is offline
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Default Stumped!!! Cooling Fan Won't Turn On!

I have a 2000 Dodge Grand Caravan that has 195,000 miles. My radiator fan won't turn on and I'm stumped!

The issue presented itself with a check engine light and the radiator cooling fan not turning on. The trouble code indicated the cooling fan relay was faulty. In all cases below, I tested the radiator fan by turning on the air conditioning (thus forcing the cooling fans to run) and also for it to come up to a high temperature coming close to the danger zone.

1. Fuse - first tested the fuse and it was OK. Had to start with simple things first.

2. Cooling fan relay - I replaced the relay which has a reputation for failing on the Dodge. Still the fan did not kick in.

3. Cooling fans - tested the cooling fans and the motor was seized. Replaced the cooling fans and tested them by jumping them. The cooling fans still do not turn on. There is no voltage leaving the cooling fan relay and coming into the cooling fan harness.

4. Wiring - tested the wiring between the relay and the fans. They checked out OK (good continuity and resistance check). There is no voltage leaving the cooling fan relay. Now it's getting more complicated... I unplugged the wiring harness from the ECM and tested the wiring between the ECM and the cooling fan relay. A-OK.

5. ECM - it is unclear how to check the ECM for functionality of the cooling fan. There are 3 wires (supply, ground, and switch wire?) The supply voltage and ground is good, but I don't know what voltage the switch wire should be. I've read that it is pulse width modulated so I can't measure this with a simple voltmeter. I've also read that the switch wire goes to ground thus triggering the relay. I don't know which is correct.

Several mechanics I talked to were skeptical that the issue is with the ECM, they knew of very few instances of this being the culprit. I even replaced the new cooling fan relay with another new cooling fan relay on the off chance that the replacement was faulty. Also because I was running out of ideas!

Did I miss something in my logic and diagnostics? I've run out of ideas and have resorted to wiring a switch directly to the cooling fans and toggling them on and off. Any help in diagnosing this problem is greatly appreciated! Thanks!
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Old 03-08-2011, 11:58 PM
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master tech master tech is offline
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Welcome to DF
The caravans also had a problem with Fan modules too. Ck the power and ground with a test lite.
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Old 03-09-2011, 01:44 AM
Cougar41 Cougar41 is offline
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Checking fuses is always step one.

Just to clarify, are you getting 12vdc at contact 4 of the fan relay connector at all times, key on or off? Do you have solid continuity at contact 1 to ground? Jumping contacts 3 and 4 at the connector still gave you dead fans?

Remind me. What was the fault code?
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Old 03-09-2011, 12:33 PM
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The radiator fan relay is a module the PCM controls and can run the fans at variable speeds. There is 12v fed to the relay and ground. There is an output wire to the fan motors and the control wire from the PCM. Check for power and ground at the fan relay connector with a test light and you should have a very bright lamp. Jumping 12v to the fan motor wire should run the fans, if not, problem with wiring or motors. If all of those are ok, check the relay control wire for opens, shorts to ground or power. If all that is ok, then lean toward the PCM being faulty.


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Old 03-10-2011, 05:38 PM
vitual vitual is offline
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Try grounding the switch signal to relay at different levels all the way backward to ECM.
go to following for complete diagnostic steps
http://dodgeforum.com/forum/2278384-post5.html
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Old 06-21-2011, 10:31 PM
ausmcvet ausmcvet is offline
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Default stumped 2!!

I'm having many of the same issues. Check engine light on--I do not know the code however. Cooling fans do not run--I didn't try and check the condenser fan, as the AC has been broken for years. When this first presented the fuse was blown, i installed another one and it blew as well. Got more fuses.... Here's what I have done so far

1. Replaced the cooling fan relay.
2. Replaced the temp. sensor.
3. Replaced the cooling fans.
4. Checked the wiring between the relay and fan motor connectors-good.
5. When I jumped 12 volts directly to the old cooling fans they would not run.
When I jumped 12 volts directly to the new cooling fans they worked fine.
6. I hooked up new fans to their connectors and jumped terminals 3 & 4 at the relay harness and the fans ran fine.
7. I checked resistance between pin 2 at the relay and PCM pin 73--less than 5 volts.

Yes I did replace the fuse and they are not blowing anymore. Fans will not run when I let the car come up to temp.

Looking at some of the other answers here I followed the troubleshooting procedure as far as I could, but then did not know where some components were located--IPM2 and IPM3??

Any help would be appreciated--it's my wife's car and she is on vacation and carless-not a happy camper

Last edited by ausmcvet; 06-21-2011 at 10:33 PM.. Reason: Added clarification
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Old 06-21-2011, 11:57 PM
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Welcome to DF
First thing I would do, is hook up a DRB3 and actuate the fan. Or a scanner that can actuate the fan.
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Old 06-22-2011, 01:00 AM
steak59 steak59 is offline
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Check the ground circuit of the Relay, Pin 1 to ground. use a test light, 1 end to B+, and stick the other end into Pin 1, see if it lights up.
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Old 06-22-2011, 11:12 AM
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Ok, thanks I'll try that.
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Old 06-22-2011, 11:15 AM
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Thanks steak. I already checked the ground and it's good. I forgot to put that in my original post.
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Old 06-22-2011, 11:15 AM
 
 
 
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