Overheating Issue
 

I have a 1996 Cherokee Sport that blew the heater control valve. Replaced that but still over heating. Replaced thermostat and then it wouldn't start like the fuel pump failed. Got it to cough to life and eventually the idle settled out, and a check engine light came on with it. Temp gauge started waving back and forth between stone cold and 210. Noticed that electric fan was not coming on. Checked relay by swapping with a known working relay still no fan. Found a blown fuse for blower motor(cavity5 30 amp) and replaced. Check engine light went off. According to temp gauge it was running at 195 or so but electric fan never came on. Took for test ride and got temp to rise to 210, still no fan action, 30 amp fuse not blown. Now I am not sure it the temperature sending unit is bad, or my fan has just died, or my Jeep has gremlins. Hoping someone here might have some advice to offer. Thanks in advance.

Hey, Russ, welcome to the forum. :cheers:

Sorry to hear you replaced the heater control valve. It's much better just to put in new hoses (one 5/8" and one 3/4") and cap the vacuum lines that used to control the HCV. It's not needed. 97 and up don't have it, and lots of forum members have removed theirs, even folks who live in hot climates.

Okay, sounds like you had a bit of a roller coaster, but all is well. The fan doesn't come on until about 218, IIRC, so it's no problem that it's not coming on. If you turn on the AC (assuming that's all working correctly), it should also come on. Typically, these beasts run about 210 if all is working correctly, so, no problem.


You might want to jumper 12v to your fan just to be sure it's functional. Polarity won't matter for this test - if it's wrong you'll just spin the fan backwards. It won't hurt anything. There's a connector near the fan; you can just unplug it and run some jumper wire (18 gauge should be fine for this) from the battery to the fan.

Electrical work is not everybody's favorite thing, so if you need more details on that, just holler. That's what we're here for! :thumbsup:

Does the fan come on when you turn the AC on? Unless you have the AC on the fan shouldn't come on until the temp gets around 215* or so.

Thanks for the replies, I appreciate it. I had already decided to do away with the Heater control valve after reading up on it here. A/C does not work for cooling, but the fan did, until I just went out to check, now its out of commission but fuse not blown oddly enough. I'm through fooling with it today, had too much fun already. I'll give it a fresh start after a strong cup of coffee in the morning. I used to volunteer on a race team back in the day, and the team owner is going to help me out tomorrow with the electrical troubleshooting. I really love my old Jeep, and will conquer this problem one way or another, I'll update this thread if anything of interest takes place. Thanks again fellas, this is a fantastic community and resource.

I'm willing to bet you still have air in the system which should eventually burp out. You can also loosen the coolant temp gauge at the back drivers corner of the head to let the air out. Should be sticking straight up with a single wire to it.

I'm familiar with that coolant temp gauge, that's a good idea. Thank you.

My jeep is all squared away again. Thanks for the advice/help. All issues resolved, running like it always has, great.

so what was the issue?

There were no electrical issue's as far as the fan goes. While tracking the coolant system issue the radiator cap got "vacuum suctioned" onto the radiator, and the rubber seal developed a tiny tear. I replaced that and the thermostat. I followed lawsoncl's advice to burp air out of system. The temp gauge going back and forth briefly is still a mystery to me. The idle issue settled out after all coolant system repairs, and the check engine light went off the next and remains off. It now runs a few degrees cooler than it used to as well. I will remove the heater control valve from the system this weekend to do away with that guaranteed future failure.

Thanks for the update. Good job tracking down the issue.

Yessir. Thanks for the interest and help, as I said this is a great "place" to be..