I have spent most of the day in here reading the previous posts and I have not run across the same headache that I have got. A big Thank you to those that help.
The Jeep:
1995 Cherokee Sport (Stock)
4.0 L 6 cylinder
269,000 miles, but as you know a vehicle that makes it that far has been taken care of. Engine was rebuilt at 155000 miles, transmission is original.
The problem: 1995 Cherokee likes to over heat in traffic, today it was 52 degrees and it almost overheated waiting for two lights. Once moving the temp comes right back down. The Aux fan will not come on at 220 degrees.
Parts Replaced with new:
Radiator, Fan clutch, water pump, heater core bypass valve, All coolant hoses, installed new spring in bottom radiator hose, coolant, temp sensors, vacuum lines, transmission lines, transmission and transfer case were serviced.
Trouble shooting so far:
I have had a leak down test performed on the cooling system and over night it did not drop any pressure. I also tested for a head gasket with the chemical test and it came up negative. Compression is in 160's across all cylinders.
I have tested the Aux fan by jumping across the relay and the fan powers up. So I know the Fan is good. I tested the relay and it was good, however I replaced it to be sure and both temp sending units. I then was not sure about the temp gage so I put in an auto meter temp gauge that had its own sending unit. (I replaced the sending unit in the back of the head for the auto meter unit. The dash gauge no longer works. This was expected.) The ground to the control side of the relay is good. The power side goes from 0-.055 volts, which is basically nothing. The relay never gets a signal
I learned in here that if I disconnect the 2 wire sending unit that the fan should power up. It does not. Also with a 470 ohm resistor in the connector the fan does not turn on. One thing that was odd was when I disconnected it, with the motor running it almost died. I then read I shouldn't unplug it with the motor running. Also this did not turn on the check engine light, which I believe it should have. Fan does not run when I turn on the ac, however the compressor is out on the ac, so I don't know if it should still kick it on or not?
The status on the Fuses, all checked and tested.
When I shut off the jeep after it has warmed up, I can hear what sounds like running water. I have not lost any coolant since it was changed.
Nothing I have read in here discusses the diode for the aux fan control. When I went to just buy one they did not know what I was talking about. Does it actually exist for this year of jeep? If not then what would you look at next? How do you test the ECU?
Thanks again for reading this!
The Jeep:
1995 Cherokee Sport (Stock)
4.0 L 6 cylinder
269,000 miles, but as you know a vehicle that makes it that far has been taken care of. Engine was rebuilt at 155000 miles, transmission is original.
The problem: 1995 Cherokee likes to over heat in traffic, today it was 52 degrees and it almost overheated waiting for two lights. Once moving the temp comes right back down. The Aux fan will not come on at 220 degrees.
Parts Replaced with new:
Radiator, Fan clutch, water pump, heater core bypass valve, All coolant hoses, installed new spring in bottom radiator hose, coolant, temp sensors, vacuum lines, transmission lines, transmission and transfer case were serviced.
Trouble shooting so far:
I have had a leak down test performed on the cooling system and over night it did not drop any pressure. I also tested for a head gasket with the chemical test and it came up negative. Compression is in 160's across all cylinders.
I have tested the Aux fan by jumping across the relay and the fan powers up. So I know the Fan is good. I tested the relay and it was good, however I replaced it to be sure and both temp sending units. I then was not sure about the temp gage so I put in an auto meter temp gauge that had its own sending unit. (I replaced the sending unit in the back of the head for the auto meter unit. The dash gauge no longer works. This was expected.) The ground to the control side of the relay is good. The power side goes from 0-.055 volts, which is basically nothing. The relay never gets a signal
I learned in here that if I disconnect the 2 wire sending unit that the fan should power up. It does not. Also with a 470 ohm resistor in the connector the fan does not turn on. One thing that was odd was when I disconnected it, with the motor running it almost died. I then read I shouldn't unplug it with the motor running. Also this did not turn on the check engine light, which I believe it should have. Fan does not run when I turn on the ac, however the compressor is out on the ac, so I don't know if it should still kick it on or not?
The status on the Fuses, all checked and tested.
When I shut off the jeep after it has warmed up, I can hear what sounds like running water. I have not lost any coolant since it was changed.
Nothing I have read in here discusses the diode for the aux fan control. When I went to just buy one they did not know what I was talking about. Does it actually exist for this year of jeep? If not then what would you look at next? How do you test the ECU?
Thanks again for reading this!
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