Hello, guys. This is the problem I am having.
2 weeks ago, my Jeep started overheating. I took a look, no MIL but it would not turn on the fan. I checked the gauges, they work, so I checked the temperature sensor then I suspected the relay under the headlight was bad, I disconnected the relay and jump the fan, it worked, so I replaced the relay with one from Napa. It worked nice, but this week the check engine light came on, code P1491 - cooling fan relay open/short circuity. I got another relay from Napa ( it was fried or defective ) and tested the amperage on the fan, it was pulling 32 amps so I replaced the fan also - it was rusted inside. Also the relay came with a new plug in the kit, so I replaced the old plug. I checked the plug installation, had 12 v coming from the relay fuse, fan would come on jumped on the plug ( < 1 amp with new motor), ground wire with 0 ohms - good ground. Now I am back to the beginning, where the truck overheats but it will not give a code, it turned on once by pressing the A/C button but it went blank after. The original relay was replaced few years ago and the first one I replaced the chip inside was toasted ( I opened up it to take a look…).
Is there another temperature sensor that turns on the relay trough the PCM ?
Would the next step be check the wire from the pin 17 to the connector ? Would anybody done that before ? Should I get a relay from the jeep dealer ?
I searched through the forum already and the internet and could not find too much info, other than this is a common problem with this Jeep.
Thank you for any help here, have a good day.
It might not be a good idea for you. But if things get bad enough to save your motor you could wire a direct switch to the fan that can turn the fan off or on at anytime. This could be a permanent fix or just long enough to fix it the original way.
Are You Sure That Faulty Fan Operation Is Now Causing The Overheating ?
I have seen situations whereby once air gets into the cooling system (not a Jeep, specifically) and rises to the high spots ( where the sensor(s) are ), the temperature indication, fan operation, and coolant flow, are altered. I’d try purging the system while refilling and see if there’s any change. If it works for a while and then reverts back, you’ve got air getting into the system.
CSA
Thank you for the answers. I tested the connector, fan works when jumped, ground is good at both sides, pcm is grounding the relay. It is a bad relay, just lasted one time, part is not good.
It appears you got things working now. Your reading of less than 1 amp of current to the fan motor seems incorrect to me. It must be more than that I would think but as long as the fan is working that is what is important here.
Thank you for your help. The problem is in the circuitry for the A/C, when it kicks on it fries the relay. So I disabled it and so far no problems, I will try to find the short later, too hot today. Thank you.
By the way, it pulls 24 amps, not <1 sorry for the mistake, Cougar.
Well, I had a failed relay. I open up the relay and there was a cut across the planar board, it is black on the attachment. So I got another one from Norwood auto parts ($46 RY330T) made by Standard - in the USA this time. It is working just fine, I isolated the A/C as the problem, but it may be just a cheap board. I soldered past the broken part on the board and I will use it to test it and do a voltage drop, I will have to redo the splice to the ground - the black wire - and see how it will work. It is pulling 24 amps on the fan side and it is not enough wire or leg on the controller to run that, I find amazing it works at all. No wonder why it fries. See the pics.