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Hydraulic Fan test/diagnosis

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AsphaltCowboy

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Discussion starter · #1 ·
During a recent road trip I started having problems with the jeep getting hot. The hydraulic cooling fan is not coming on. The fan spins freely by hand(with engine off) so it's not the bearings or motor. The fan spins slowly at idle(as it normally does) but will not speed up when the AC comes on or when the engine gets hot.

I believe it is the control solenoid and I'm trying to see how to test it. There is a 3 wire connector that goes to the solenoid however only 2 of the wires actually enter the solenoid(the other is a ground way down by the solenoid it's self).

I want to test the engine side of the 3wire connector to see if the ECM is in fact trying to tell the fan to turn on/ramp up and I'd like to know which wires to provide power to on the solenoid side of the 3wire connector to try to manually force the fan to go to full power.

I have tried unplugging the coolant sensor and that did not change fan speed.

The power steering feels fine and the fluid is clean and full. No hose leaks either.

I know what the fan looks/sounds like at medium and high speed and can say for certain no matter what the condition it never leaves it's slow idle speed. This was never a problem until the other day.

Thanks!
 
#4 ·
I know this isn't any help at all, but mine is doing exactly the same.
It originally had the CEL on due to a P1499 fault but after a swap of hydraulic fan solenoids that went away yet the fan doesn't actually work any harder under load.

Waiting to see other responses.
 
#5 ·
You mean the water pump I assume and that is the hydraulic/mechanical fan. The hydraulic part is the fan clutch which appears to be bad on yours. You have the 2 fans, an electric fan and a mechanical/hydraulic fan and it is attached to the water pump not the PS pump. Do what I told you to do above to check the fan clutch.
 
#6 ·
nickblack said:
You mean the water pump I assume and that is the hydraulic/mechanical fan. The hydraulic part is the fan clutch which appears to be bad on yours. You have the 2 fans, an electric fan and a mechanical/hydraulic fan and it is attached to the water pump not the PS pump. Do what I told you to do above to check the fan clutch.
Click to expand...
You really have no idea what you are talking about here. There is one fan and it does run off the power steering pump.

I was having power steering pump issues recently and ended up running it empty for a few days (had no choice at the time) Replaced the pump, but now my fan will not speed up either. Im afraid I may have burnt up the motor, but interested in seeing where this thread goes...
 
#7 ·
nickblack said:
You mean the water pump I assume and that is the hydraulic/mechanical fan. The hydraulic part is the fan clutch which appears to be bad on yours. You have the 2 fans, an electric fan and a mechanical/hydraulic fan and it is attached to the water pump not the PS pump. Do what I told you to do above to check the fan clutch.
Click to expand...
99 and 00 WJ V8s have a mechanical fan, 01+ have a hydraulic fan attached to the PS pump.
 
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#10 ·
ezflip said:
You didn't offend me, I was simply correcting you. But apparently you cannot take being wrong...lighten up. :tea:
Click to expand...
Some people you can never say anything right to... A new fan assembly is like $1000, depending on where you live. They don't sell the solenoid alone, so it kinda sucks. Champ and Quadratoken both part out WJ's and sell the fans. I can give you there #'s to see if they can hook you up.
 
#11 ·
Hope none of what I say angers ezflip :-/

You can run 12v to the solenoid connector (there's a connector behind the headlight) and test to see if it's working. I believe power goes to the green/red connector.

This is how I did it using speaker wire

Image


The PCM can be an issue, I'm not sure how to test it but there's a company in Florida that can test and flash a replacement for you.

If it is the solenoid that kinda sucks, it's a case of finding one from a breakers, buying a new assembly or perhaps investigating the Crown Vic one that looks like it could be modified to fit.
 
#15 ·
Pulling the engine temp connector should have forced to PCM into applying a full 12v to the fan with engine running.

Putting a external 12v on the connector going to the solenoid will reveal your next step. If it still doesn't spin faster its hyd fan unit if it sounds like a airplane its PCM or wiring between the two.
 
#16 ·
The attached pinout diagram is from an 03 FSM. Omit references to "diesel."

The OR/DG wire (pin 1) from the ASD relay carries 12V to the solenoid.

The LG wire (pin 2) brings the fan control signal from the PCM. The PCM signal on this wire is almost certainly a pulse width modulation (PWM) signal which turns on and off the 12V moving the solenoid and controlling the fan speed.

The BK wire (pin 3) is connected to ground.

With the key on, there should be 12V on pin 1. There shouldn't be a signal on pin 2 unless the engine is running. With engine running, the fan control signal, if there is one, should be close to a 5V square wave. However, you would need an oscilloscope to to view it. A digital voltmeter should give some type of response, but not very useful, if there is a signal from the PCM.

Some have indicated (see post #15) that disconnecting the engine coolant temp sensor (no engine temp info going to the PCM) will cause the fan to run at full speed. That seems reasonable because for engine safety reasons the PCM probably would default to a steady 5V signal allowing 12V to be applied to the solenoid continuously causing the solenoid valve open to the full speed position. However, if the wire to pin 2 is faulty or if the PCM is faulty, I don't believe the fan will run full speed because there won't be a 5V control signal from the PCM.
 

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