Fan relay problems - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 19 Old 06-20-2017, 09:22 AM Thread Starter
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Fan relay problems

hey. some time ago i noticed my jeeps temperature going up, and upon further inspection, i realized the fan relay had gone bad, so i replaced it. and, i kept a spare in the glove box, just in case....

well, about a month ago, i was at a stoplight, when i noticed the temp almost at 3/4 and increasing... so i quickly grabbed the spare relay, and replaced it there at the light... this immediately turned ON the fan and lowered the temperature...

now, yesterday i was driving on the highway, when again, the temp was increasing... this time i wasnt as quick, as i couldnt stop immediately, and the HOT TEMP light went ON.... since i had no spare now, i pulled a relay from my aux lights and replaced the one of the fan, and again, the fan turned ON immediately...

so, Im wondering, why are the relays blowing?? maybe the fan is not running smoothly and this causes more amps to pass through the relay?? i dont know if it matters, but when it happened last month, i was pulling my bassboat, and yesterday i was also pulling a trailer and i was going uphill.... besides yesterday the air temp was 110+ here in the Chihuahua desert just south of Texas....

what could i do, besided having lots of spare relays??

2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....

Last edited by shu2kill; 06-20-2017 at 11:36 AM.
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post #2 of 19 Old 06-20-2017, 09:43 AM Thread Starter
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from what im reading, i replaced the high speed relay, the one behind the drivers headlight...

also, yesterday i had the A/C ON at max.... one month ago, it was OFF, as it normally is.... yesterday it blew within the first 1/2 hour of driving it...

2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #3 of 19 Old 06-20-2017, 10:51 AM
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You talk of relays, then suddenly ask why are the fuses blowing.
So I'm not sure what you are dealing with.

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post #4 of 19 Old 06-20-2017, 11:37 AM Thread Starter
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Quote:
Originally Posted by ronjenx View Post
You talk of relays, then suddenly ask why are the fuses blowing.
So I'm not sure what you are dealing with.
sorry, i just edited... no fuses are blowing, only relays are going bad... thats what happen when i think slow and type fast...

2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #5 of 19 Old 06-20-2017, 11:47 AM
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Have you looked at the bad relays to see if it's the coils or the points that are burning out?

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post #6 of 19 Old 06-22-2017, 07:50 PM Thread Starter
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I didnt check on the previous ones, but on this last one, blade 87 seems like it melted a bit, ill post a pic later tonight
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post #7 of 19 Old 07-06-2017, 07:22 PM Thread Starter
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today it happened again... i had a spare, so i replaced it before the temp reached 3/4 of the gauge, but still, i need to fix the problem asap...

this is the relay i removed. blade 87 seems melted...


2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #8 of 19 Old 07-06-2017, 09:07 PM
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Quote:
Originally Posted by shu2kill View Post
today it happened again... i had a spare, so i replaced it before the temp reached 3/4 of the gauge, but still, i need to fix the problem asap...

this is the relay i removed. blade 87 seems melted...

Photobucket no longer works. Can you post the picture through another hosting site?

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post #9 of 19 Old 07-06-2017, 09:25 PM Thread Starter
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One more try... not the best picture but you can see the melted plastic...
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2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #10 of 19 Old 07-06-2017, 10:47 PM
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Next step would be take the cover off and see what's going on inside.

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post #11 of 19 Old 07-11-2017, 10:51 AM Thread Starter
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well, i took it to a mechanic, and he says the problem may be the low speed not working, so it makes the high speed work a lot, until it burns the relay....

i guess this could be correct, because i can hear the fan turning ON very frequently, sometimes within 30 seconds it will stop and then star again...

so, is there a low speed relay or something?? i found on another thread someone mentioned a low speed fuse in the fuse box, but i checked and its not blown....

the mechanic said the problem could be the plug located on the top part of the fan, on the pasengers side. this one: (not my pic, but the same piece)


2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #12 of 19 Old 07-18-2017, 05:40 PM
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Your problem is not the plug, but may be the voltage divider that is behind the plug. Your JEEP is a 2007 which has a two speed fan. The relay you are burning out is the high speed relay. The fan is designed to come on in stages to minimize over-current shock load. If the low stage is not coming on, the in-rush will be too much for the relay to handle. Check your voltage divider output for current operation.
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post #13 of 19 Old 07-21-2017, 12:35 PM Thread Starter
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Quote:
Originally Posted by JohnPShoe View Post
Your problem is not the plug, but may be the voltage divider that is behind the plug. Your JEEP is a 2007 which has a two speed fan. The relay you are burning out is the high speed relay. The fan is designed to come on in stages to minimize over-current shock load. If the low stage is not coming on, the in-rush will be too much for the relay to handle. Check your voltage divider output for current operation.

thanx!!

any pointar as to where is the voltage divider, and how to check it??

2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #14 of 19 Old 07-23-2017, 08:07 PM
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It's a cylindrical resistor(?) near the plug in the picture you posted. Has a screw holding the assembly onto the fan shroud.

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post #15 of 19 Old 07-25-2017, 03:47 PM Thread Starter
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Quote:
Originally Posted by MicroMark View Post
It's a cylindrical resistor(?) near the plug in the picture you posted. Has a screw holding the assembly onto the fan shroud.
thank you!!

is there any way of knowing if it is faulty or working properly??

2007 JKU, 2.5" Rock Krawler lift, 285/70 17 mud terrains....
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post #16 of 19 Old 10-27-2017, 12:38 PM
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I hope you figured out your problem, but I am also dealing with a fan mystery.

Apparently the resister drops 12 v power to 8v on the GREEN wire, so the fan runs on low speed. When the TIPM and computer think the fan needs to run on high speed, the high speed relay kicks in, sending 12 v to the other wire. Thatís what I have gathered thus far. My fan operates normal, low and high, until on a rare occasion, it will simply not come on at all. I turn the Jeep of, turn it back on, and it runs on high to cool itself down, then operates normal again. I have learned very quickly to keep an eye on my temp gauge!
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post #17 of 19 Old 10-28-2017, 08:28 AM
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yep. Itís a thermistor or voltage divider setup that is a cheap means of causing a single wound ( single speed) fan to operate at dual rates based upon the current step-down by the resister component. When that thing gets really dirty or just brittle and the ceramic cracks, it can cause crap like OP experienced, fwiw ( and a little late to the thread)




(edit: if you care about heat and ride your jk hard it is a good upgrade to go with a greater CFM fan that is waterproof. Spal makes awesome fans a lot of us run on these 3.8l JKs)






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Last edited by j3ff3ry_j33p; 10-28-2017 at 08:32 AM.
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post #18 of 19 Old 10-28-2017, 02:17 PM
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I had a similar issue with the fan running intermittently. The cause was the connection into the actual fan itself. Although there was resistance when plugging it in, the earth contact was loose, evident by burn marks on the terminal. Something to check.
I'm running the OEM fan on a Hemi swapped unit and fan does a top job of keeping her cool. Nothing wrong with these units unless mud is your thing...
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post #19 of 19 Old 10-27-2018, 07:37 PM
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