Electrical fan gremlins???

My wifes 98 2wd xj 4.0 has been overheating a little here and there, so i did the usual, new t-stat, cap, water pump is already new, fan clutch is good, electric fan wasnt comming on at all, relay is good, and fan works great when hard wired, my temporary fix solved overheating problem. I pulled relay and hard wired fan with a inline 30amp fuse from the switched power slot where relay was , so fan comes on when you turn the key on, no overheating now driving around today for 35 minutes stop and go with a/c on high and it was 110 degrees out, but now check engine light stays on, (no big deal) but when you turn car off it beeps like you have key in ignition and door is open and stays running for about 5 seconds then dies. all fuses and relays in the fuse block are working , Is there another relay or fuse somewhere? I would like to fix this right, any advice would be great.

First, a**uming you have a 50/50 mix ethylene glycol and distilled water. Cut it to 30 ethylene glycol and 70 distilled water, that will give you an immediate improvement in cooling.

You are getting a CEL because the PCM is supposed to be controlling the aux fan based on input from the CTS in the thermostat housing. I would put things back to the way they were and test/replace the CTS.

What do you consider to be overheating a little? How do you know the fan hasn't been coming on when it's supposed to?

ehall said:

What do you consider to be overheating a little? How do you know the fan hasn't been coming on when it's supposed to?

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fan doesnt come on at all even when temp gets near 250 and water is spilling from overflow. i scanned codes today and came up with 1491 which was fan relay, i put relay back in code goes away, also came up with 1389 which isnt in the book i have, also when i was fixing cooling problem a/c clutch was engaging then disengaging repeatedly with a/c on high, today it took ten minutes for a/c to blow cold and after another 15 minutes it stopped blowing cold and now doesnt work and now the a/c clutch wont engage, thought it might be low on refrigerant, tried filling but still wont engage, tried putting fan relay back in still nothing, the fuse for the ac clutch is good also. ac worked great before.

If it's 98 then the gauge and ECM are fed from the same temperature sensor in the thermostat housing. That means the control side of the circuit isn't working, which appears to be confirmed by your experimentation with the relay. You probably ought to replace the one you've got. Hopefully that fixes it.

Your A/C problems could be related, I'm not sure about the later models but its not uncommon for the high pressure switch to force the compressor off when temperature gets too high.

yeah i did some more research and found out the relay for electric fan controls ac clutch too. I jumped the wire for the clutch it is good, pluged it back in and started it and ac worked, made sure refrigerant was full drove it and little while later stopped working again, must be the sensor in the thermostat housing.

P1389 is No ASD Relay Output Voltage At PCM. Did you swap relays around while testing?

When we pulled the plug to the coolant temp sensor on my buddys 93 while it was running the electrical fan came on by default. He replaced the coolant temp sensor and now everything works fine. You might want to put everything back the way it was and give that a try, it would save you from all the other problems your running into now.

hubs97xj said:

P1389 is No ASD Relay Output Voltage At PCM. Did you swap relays around while testing?

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yeah put it back, i bought the sensor that plugs into thermostat housing today and wil replace it tommorrow, should do the trick.