tommy88

Hi all,

I have a 94 xj 4.0 i6, auto.

My electric fan doesn't come on with temperature, it does, however, come on when I turn the A/C on and when I unplug the coolant temp sensor (CTS).

I put in a new CTS today and let it idle all the way up to about 235 degrees and it still won't come on.

Any ideas?

car5car

Check fan, wires and relay.
Current is pretty high, check connectors.

mehoff_400

had the same problem...changed the relay fixed it

tommy88

Thanks for quick replies! Will check relay next. Is the AC relay the same? In other words, can I plug the AC relay into the fan spot and check if it works that way to make sure it's the relay?

Also, do I need to put RTV sealant on the CTS? I did on the threading just in case, but if the CTS wasn't the problem, I'll return it and put the old one back in.

tommy88

Actually, doesn't that diagram you attached show that if the fan is turning on with the AC that the relay is fine? The AC is still activating the fan through the fan relay, right? and not directly from AC relay?

Sorry if my questions are dumb, I'm pretty new at this..

I'm also going to get a voltmeter to test CTS resistance at different temperatures to rule out that the new CTS I got is also bad. If the CTS is good, the only explanation I can find is bad ECU...

reyeskid

you hit 235 idling? damn

tommy88

after about 30 mins, yea

car5car

All relays are standard. If they look alike and have same number of pins switch it.

car5car

Yes

tommy88

I got a multimeter and measured the resistance of the new CTS directly at the CTS by unplugging it from the harness and testing the pins inside the connector. I got about 670 ohms, which is within the range for the operating temperature.. however, the electric fan only turned on when the gauge went all the way up to the 3/4 mark (i think that's 235)..

Is that a sign of a bad PCM? Or just that the gauge reading is off because of a bad coolant temp sending unit? (which is the one that the gauge reads from, located on top rear driver side of engine). Gauge operation seems completely normal other than that...

tobtech

I have a 1998 Cherokee and my electric fan only comes on with the AC as well. I think it has been this way for a long time. I just figured it never got hot enough to come on, usually the hottest it will get is 220 on rare occasions. So I guess I have the same question, is there something wrong?

And also I would like to wire a switch to manually trigger the fan relay so for slow driving or off-roading I can turn on the fan. This diagram is great. I should be able to wire a switch to throw a ground to the Dark Blue/with Pink tracer. Has anyone ever done this? If the computer does not like seeing a ground on that wire when it should not be there, I can throw a relay on the wire so that I only send ground into the fan relay.

Thoughts?

Jay420

Done it on my 92 Cherokee and works awesome. No codes.

tobtech

Thanks Jay! Then I'm gonna do some wiring this weekend then, aux fan switch and some new lighting

djb383

I presume u won't be using a/c while off-roading. So, if u unplug the a/c clutch relay (in fuse box on passenger side fender), a/c will not work but the rad efan will when u select a/c with the vent selector switch on the dash. When u want a/c, pop the relay back in.



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xjfirefighter

Wish I found this thread sunday