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dustincstn82 08-28-2013 11:22 AM

WJ Raditor fan relay woes
My girlfriends 1999 4.0 had a relay go out and I've tried both that are available from Autozone and they don't last more than a week. I've even installed a heatsink to keep this from overheating because I saw that this was a problem for the relay. Iat this point I'm worrying that either a Jeep brand relay is the difference or I need to chase for a short. Any help here towards the typical problem would be great!

Frango100 08-28-2013 03:21 PM

Re: WJ Raditor fan relay woes
Welcome to the garage.
Not sure about the quality of the autozone relays, but many times the fan is the culprit. It still works, but will draw too much current, which finally fries the relay.

dustincstn82 08-28-2013 03:34 PM

Thanks! When I started this process we replaced the fan along with the thermostat

Frango100 08-28-2013 03:42 PM

Re: WJ Raditor fan relay woes
Did you check if it is not running all the time when the engine gets at operating temperature?

dustincstn82 08-28-2013 04:56 PM

Yes. It overheats rapidly because the fan doesn't turn on at all.

2005JGC 08-29-2013 03:11 PM

Re: WJ Raditor fan relay woes
If you dont have any way of measuring the current the fan is drawing then I would replace BOTH the fan and the relay with new. If it works with a new relay it is a pretty good indication that the circuit is intact. As frank said, the fan will draw too much current and kill the relay. that is the ONLY draw on the circuit, so if it works with a new relay you know there is not a short and the wires start and end where they are supposed to, the only current decider is the fan.

dino2004 03-11-2014 12:23 AM

Hi i have a 2004 grand cherokee special edition it overheat at idle only . When driving its ok so wen i stop the car and look at fan its off i changed the temp control sensor next to tge thermostate but that was for the temp gauge inside is there another sensor somewhere else that might have gone bad that tells fan go go on ?

Frango100 03-11-2014 08:03 AM

Re: WJ Raditor fan relay woes
1 Attachment(s)
Welcome to the garage.
You have the 4.0 engine? (4.7 has hydraulic fan setup, which always idles when engine runs)
Either way, there is only one engine coolant temp sensor. It gives the coolant temperature information to the PCM, which sends it to the instrument cluster for indication and uses the signal for several calculations for injection and spark, but also for the cooling fan off/on signal.
The 2004 model has two relays in the PDC (Power Distribution Center) under the hood; a low speed and a high speed relay. You could swap the low speed relay with a known good one. You can also put 12v directly on the fan motor, to check if it works ok. Many times the fan motor start drawing too much current and fries the relay (at least this happens a lot on the pre 2004 models with a PWM relay under the right headlight (As seen from drivers position))

dino2004 03-11-2014 08:15 AM

Ok thanks ill check it out

DeucesALLin 03-11-2014 09:21 AM

Re: WJ Raditor fan relay woes

In my JK I decided to use a lifetime replacement fan from Advanced for $120 instead of the $200 OEM unit. I did however install a switch to kill it during crossings. Zero failures.

I know that JK's that went to Egypt had mechanical fans and alot of the JK crowd were switching to those with dealer parts. Since WJs went all over the world, has anyone researched if this is an option?

dino2004 03-11-2014 10:00 AM

I only overheat when at ifle more than 7 minutes cause fan is not going on

Frango100 03-11-2014 10:27 AM

Re: WJ Raditor fan relay woes
If you want to check for voltage, i had added the wiring to my previous post.

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