1995 Jeep Cherokee Check engine light from the radiator fan

CHEROKEE1000

MEMBER
1995 JEEP CHEROKEE
6 CYL
4WD
MANUAL
155,000 MILES

The check engine light comes on when I start the engine on my 1995 cherokee. The OBD gives error code 35 (suggesting a problem in the radiator fan circuit). The battery is also not charging suggesting there is a short somewhere in the system.

The fan does work as it runs while the a/c is on. I am thinking it might be a problem somewhere in the heat sensor that runs the fan when the engine gets hot.

Does anyone have any suggestions of where I should look to trace the problem or the parts I should replace?

Thanks

1 Reply

INTERNETMECHANIC

MECHANIC
700 POSTS

The coolant temp sensor shows to be in the thermostat housing. I can't say that the sensor is faulty? The pcm may use a 5 volt ref signal to the sensor. The other circuit is ground. High resistance through the sensor when engine is cold. As the engine warms up, the resistance to ground through the sensor starts going down, the ref voltage starts dropping, the computer monitors the ref voltage. I can give you resistance spec for the sensor at different temps. You can use a digital multimeter to check voltage and ground at the sensor connector. With the key off, take connector loose from sensor, place meter leads between wiring connector terminals, turn the key on, you don't have to start it. If the meter reads close to 5 volts, you have voltage and ground.

Generic specs for sensor resistance, 3400 ohms at 70 degrees F, 1600 ohms at 100 degrees, 185 ohms at 212 degrees.