Ok, went to the shack today and they only had 470 Ohm resistors. The test called for 450 but I'm sure these will do just fine. When I get a chance I'll try it today. (I'm at work)

 

Have you tried just unplugging coolant temp and starting the motor fan should come on .

 

Good work.

The test does call for a 470 Ohm resistor.

 

Honestly... No I didn't do that. With an open circuit there there computer will think it's hot enough to need the fan on? I'm going to try it with the resistor before I get outta here

 

Freegdr,

I've seen this unplugging process mentioned many times in the forums and I still can't figure out what pupose it would serve (other than testing the PCM's ability to trigger a CEL).

Can you school me on this?

 

Back when I was working garages a quick test for bad coolant sensors was unplug them circuit goes into a fail safe mode triggering cooling fan to come on .

 

Just unplug the coolant temperature sensor at the thermostat housing. No fancy test or resistors needed. If it still doesn't come on make sure the fan works by unplugging it and running 12volt jumper wires from the battery, if it doesn't come on then, the fan is dead. You're making this way to hard on yourself man, easy 5 min job to check if that

 

But if you read the thread you would see i already used my power probe to do that. The fan is good. This is way deeper than just seeing if the fan works. I wouldn't make a thread for that...

I'm going to use the resistor and test it tomorrow morning. I already bought it and just unplugging the sensor and the fan coming on doesn't make much sense. But I'll try that after I test it with the resistor in place and see if that trick actually works.

 

If you do this be prepared to clear the DTC code P0118 (ECT Sensor Voltage Too High) when you're done.

 

Ok, I performed the test and the fan came on and went off as it should. No CEL from this test.

I did not try the other method... I could have just erased the code with my scanner but the resistor worked oerfectly actuslly.

So I guess that answers my questions. The fan works as it should, it's not coming on when I have the a/c on because of low pressure in the system, and I haven't noticed it in traffic because the jeep just hasn't gotten hot enough to engage it! Thanks even big thanks to CCKen!

With all of this new found info I'd say I'm well prepared to diagnose and repair my friends aux fan problem too. When I get a chance to look at it ill add more info to the thread!

 

X2^^^^

 

Excellent.

If you need indepth troubleshooting help with your friend's fan circuit let us know. That is to say it fails the test.

Edit: I like the evidence of the temp gauge pic.

 

This isn't the correct way to test it though...

 

Sounds good. Thanks again! And I just wanted to include some good pics if anyone has this problem down the road on the off chance they use the search key. Lol

 

Theres more than one way to skin a cat ,some take 5 minutes and others take 3days . Get our point ....