I have a 94 3.5 with an overheating problem. It only gets hot when driving slow or idling so I thought this might be a radiator fan problem. Sure enough when I checked, the fans were just sitting there off. I replaced the coolant temperature sensor and it still does not come on. I also ohmed out the two fan relays and they are good (75 ohms). I also swapped them with the wiper relays which are the same part number. When I turn on the AC, the fans work fine so the fan motor is good. When I run the AC, the whole car stays fairly cool and doesn't overheat so the fans must be running okay. What could be causing my fans to not come on? I figure the sensor tells the onboard computer to turn the fans on and then it goes through the relays and straight to the fan motor....? I replaced the sensor and checked the relays, so I do not know what else could cause it besides the PCM. Any help would be great.
I also checked my connections to the fan and the Radio Frequency Interference module. I also cleaned the contacts to the Coolant Sensor and the Fan connector. The wires look okay from a visual standpoint.
Welcome to the site Rowdy, have you tried to change the fuses for the fans? Mine went out and because I was careless, eventually took the water pump with them.
If I had to take a wag, I'd point towards the PCM too. If I remember correctly, the PCM has control of the fans. If it's turning them on for the A/C but not for a hot engine, then it may need reflashed or replaced possibly. You may have to go to a dealer and have them hook up the scan tool to see why the PCM isn't signaling the fans to activate properly.
Thanks for the welcome guys. The only fuses for the fans that I know of is the one fuse located in the Power Distribution box. It was good. If there was another fuse in the other fuse box, I ohmed all those out and they were good. I don't think there is anything wrong with the wiring, although there could be....
I would have to assume the PCM as well. I was just wondering if there was some other switch that I may have been missing or perhaps the Air Conditioner condenser switch was causing it. I may have to take out the fan assembly and look at all the connects. I don't have a wiring diagram in my Haynes that shows me the wiring path from the coolant sensor to the PCM-relays-fans.
I have the exact same problem,,, and for me it already took out the waterpump,and i had to have it replaced,, so out of frustration i just manually ran a wire from the fans to the dash, and if the fans dont come on,, i wired it up to the high speeds,,, and i can turn them on and offf whenever i want,,, i guess desperate times call for desperate measures ;-) however if u find a solution please be sure to post it,,
Are you sure you are letting the engine get hot enough?
Cars with electric fans have to go way above thermostat temperature to turn on and then go down to almost thermostat temperature to turn off.
I think my car has about 6 graduations between H and C.
Normally it runs on the 2nd line from C.
If the compressor is on the temp will hover just slightly above the 2nd line from C.
Without airflow through the rad it will rise to almost the 3rd line before engaging the fan.
My Shadow runs 1/3 between H and C and needs to hit 2/3's to kick in the fan.
Good point jfs. I am not sure about anyone else here but that does bring up a question for all of us. I am curious as to the rest of everyone when there fans kick in. I cannot honestly say, but I thought the fans kicked in fairly quickly, but maybe I am mistaken. The reason why I thought the fans were not being turned on was due to the fact it only overheats while idling or creeping in traffic and when I turn the AC on, it stays cool no matter how long I sit. I drove one day with the car pretty hot and close to H and I looked under the hood and the fans were not moving. When I turned on the AC, they quickly came on and cooled the car down.
Yep, my fans rarely come on if at all in the winter. My fans do turn on if the temp gauge starts to creep above the halfway mark though. If your gauge is approaching the H mark and the fans still don’t activate, then there is definitely something going on....
the problem with my car is that they dont come on at all sometimes,,,,, when they do come on its just a hair above the half way mark,, but if the fans dont come on,, it will quickley warm to the H. i tried pulling the codes and i did get one that explains that i have a problem,,, it pulled a code 35, which means: Radiator fan control relay circuit fault ,,, whatever the hell that means. anyway im going to keep flying with the manual switch,,,
Have you ohmed out your high/lo speed fan relays? You can also swap them with the wiper ones since they are the same and try that.
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