help with electric fan

[soldwrangler]

its a 91 w/4.0 H.O. the fan comes on when a/c is on. is the fan supposed to come when engine gets to a certain temp. to assist the manual fan when the a/c is off?

[beakie]

the fan should come on when the temp gets high enuf, I know mine never came on unless the A/C was on... but my engine never over heated so I am not sure when it should come on.
after all that I guess I didn't really answer your question other than yes it will come on, or should at a certain temp

[langer1]

It comes on about 215-220.

[soldwrangler]

thanks for the info. thats what its not doing

[langer1]

thanks for the info. thats what its not doing

Then test the fan thermostat down on the driver side tank in the radiator.

[goodburbon]

I was under the impression that it was supposed to come on when the jeep got hot too, but the dealership told me that it was contingent upon AC compressor head pressure, and that it was normal for the fan to not operate unless the AC was on. Not a real problem here since we have to run our AC compressors year round. I manually wired mine to come on when the jeep gets hot, but my wifes....only when the a/c is on and it is hot.

[langer1]

but the dealership told me that it was contingent
Totally untrue. Depending on the year the fan either has it's own thermostat or the ECU controls it. It does come on with the AC compressor or High engine temp.

[goodburbon]

I didn't believe him either, then I read the schematic in the FSM. It is true, (for the 2000 year model at least). It(the ECM) requires both a hot signal and an adequate head pressure signal before turning the aux fan on.

I personally think it is quite a retarded thing to do on a vehicle that has such a propensity to overheat.:explosion

[langer1]

I didn't believe him either, then I read the schematic in the FSM. It is true, (for the 2000 year model at least). It(the ECM) requires both a hot signal and an adequate head pressure signal before turning the aux fan on.

I personally think it is quite a retarded thing to do on a vehicle that has such a propensity to overheat.:explosion

The way I read it it's OR not AND.

[goodburbon]

It may be that way in previous years, In fact I seem to remember my 94 xj aux fan coming on without AC. They charged me $45 to tell me that it was normal when I was convinced that the fan should come on as the AC comes on (the 2000, not the 94).

[y-townxj]

my fan wont come on and my engine is getting hot so shouldi just wire it so its on all the time

[langer1]

my fan wont come on and my engine is getting hot so shouldi just wire it so its on all the time

You could but just remeber that those fan motors are not built to run all the time and will not last as long running all the time.
Fixing the problem would be better in the long run.

[langer1]

One other thing different about the 2000 and up is if the engine over heats the AC is disabled and the fan runs until the engine temp returns to normal.

[desertrandy]

When I rebuilt my '92 cherokee, I removed the air conditioning because all the parts were either missing or broken so I decided to save money and take it out. My electric fan still comes on when the temperature reaches about 220-225 degrees and shuts off around 205-210 degrees. I believe it is activated by the sensor that is located in the thermostat housing. Since I spend alot of time wheeling in the mojave desert and death valley area the fan has been cycling on and off alot, however, once activated it does a good job of bringing down the temps. I originally had it wired to a switch but found that it works just fine plugged into the factory harness. Also, by leaving it plugged into the harness and letting it work automatically, you don't have spend half your time watching the temp gauge.