HELP! Fan Relay

Karaus · May 5, 2015

Rebuilding my 02 Liberty that was wrecked in the front. We used all new parts from an 05. My 02 has a 2 wire plug to the electric fan, the 05 has a 3 wire plug. So, we cut off the 3 wire plug and put the old female side of the 2 wire plug onto the fan and connected it to the High speed side, then then the low speed, then both together. NOTHING.

My temp gauge inside will not move past 1 needle mark before half. It was 82 degrees yesterday i let it sit at idle for 1hr and the electric fan would still not kick on. I OHM tested the coolant sensor by the alternator and it seems to be working fine.

Possibly relay under the battery box? If i unplug the coolant sensor the fan kicks on like it should. How do you test the relay?

Im still running the mechanical fan so maybe the coolant is just not reaching the correct temp to kick on the fan. BUT, it was hot yesterday, i strongly feel there is a problem somehwere.

Is there any other ways to trick the system into turning the fan on? Im at a loss.

uss2defiant · May 5, 2015

The e-rad fan only comes on at certain conditions.

OPERATION
The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relay. The PCM regulates fan operation based on input from the engine coolant temperature sensor, battery temperature sensor,air
conditioning select switch and vehicle speed. The fan is not energized during engine cranking regardless of the electrical input from the temperature sensors and ,air conditioning switch. However, if engine operation conditions warrant fan engagement, the fan will run once engine starts.

Vehicles Equipped with AC:
In addition to using coolant temperature and battery temperature sensor to control cooling fan operation, the cooling fan will also be engaged when the ,air conditioning system is activated. The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F), or , air conditioning is selected and battery temperature sensor is above 41° C (106°F). It will then de-energize when , air conditioning is selected and coolant temperature is below 92° C (198° F), or , air conditioning is selected and battery temperature is below 38° C (100° F).

Did you check the fuse to the radiator fan relay?

renegade 04 · May 5, 2015

Yes, you can trick the jeep so that you can activate the cooling fan. I did and it was a cool mod and it would easy for you because you have only one speed but you can make it work with both high and low.

Karaus · May 5, 2015

Vehicles Equipped with AC:
In addition to using coolant temperature and battery temperature sensor to control cooling fan operation, the cooling fan will also be engaged when the ,air conditioning system is activated. The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F), or , air conditioning is selected and battery temperature sensor is above 41° C (106°F). It will then de-energize when , air conditioning is selected and coolant temperature is below 92° C (198° F), or , air conditioning is selected and battery temperature is below 38° C (100° F).

Did you check the fuse to the radiator fan relay?[/QUOTE]

My fan does not come on when i turn the ac on. Im still rebuilding the jeep so it doesnt have any coolant in the ac lines. It also has the newer style 3 wire fan on it while my jeep is the old 2 wire so i was led to believe thats why the fan does not come on when i turn the ac on. True?

Also the fuse is good. ive swapped and replaced the fuse multiple times. The only way ive been able to get the fan to kick on is unplugging the coolant sensor and providing power straight from the battery.

Can you test the relay anyway? After reading the ohms of the coolant sensor it seems to be functioning fine.

It sat at idle for around 1hour at 82 degrees F outside yesterday. Surely at that temp the coolant and battery temp would be up to par for it to kick on. My temp gauge on the cluster will not move over half.

Possibility of it just not getting hot enough? Seems unlikely.

uss2defiant · May 5, 2015

False, I think it shouldn't matter if you have a 2 speed (3 wires) versus a single speed fan (2 wires).

Without AC, the fan should still come on regardless when it gets hot enough.

If I read my 03 FSM correctly, to test whether the relay is still functioning mechanically, you can apply at +12V bias to pin 4 which is the control line of the relay. I would do this unplugged from the car. So by applying +12V on pin 4 with pin 3 as ground, pin 1 and pin 3 will be connected (use conductivity test here).

On a side note, do you have a clutch fan? If so you're still okay with just that.

If the temperature gauge is not at half, not sure whether it reached operating temperature. That would be weird if it wasn't if you were just idling it for an hour. :shrug:

uss2defiant · May 5, 2015

renegade 04 said:
Yes, you can trick the jeep so that you can activate the cooling fan. I did and it was a cool mod and it would easy for you because you have only one speed but you can make it work with both high and low.

OP: renegade 04 was referring to a manual switch to control the radiator fan.

Radiator Fan Override Switch (The Easy Way) - NAXJA Forums -::- North American XJ Association

renegade 04 · May 5, 2015

yup that is the link I used but when wiring it for the libby people need to remember that the libby turns the fan relays by opening a path to ground and not by applying positive power to the relays.

uss2defiant · May 5, 2015

renegade 04 said:
yup that is the link I used but when wiring it for the libby people need to remember that the libby turns the fan relays by opening a path to ground and not by applying positive power to the relays.

mmmm please rephrase what you just said, I don't think that is entirely correct since positive power to the relay would be to the control line of the relay to energize the coil which moves the switch in the relay.

In my 03 FSM, the relay connects +12V to the output side of the relay to the radiator fan. They may have changed that in 04 but I want to say the 02 is closer to the 03 than the 04 versions.

Karaus · May 5, 2015

yes i have a clutch fan. The factory 11 blade fan is still in there. I just drove it to the store in stop and go traffic. I have a infrared thermometer. The top radiator hose is at 228 degrees, the temp gauge in dash is sitting dead in half. Surely that would get that fan to kick on. The mechanical fan works great but we get a lot of 80-90 degree days with a lot of stop and go in the city. I would feel much more comfortable knowing the fan is working.

The relay just checked out fine.

Is there a way to check the thermostat sensor? Could i unplug it and get a piece of wire and put both ends in the female side of the plug fooling it into thinking the thermostat sensor is closed(fan on when closed)?

I still cant understand why the fan will not come on when the AC is turned on. Maybe that has to do with it not kicking on?
There are 2 blue wires and 1 black on the fan. 1 blue wire does not do anything, nomatter if i bring power straight from the battery. Im assuming this would be the high speed and i dont have anough power to activate it that way. Then a black and a yellow off the relay to the fan. Ive tried multiple combinations of wiring , but yet continues to keep me guessing.

On the 2 wires coming off the relay to the radiator fan im reading 12.6V on one wire, and 5.7V on the other wire?

uss2defiant · May 5, 2015

Important part to note:

uss2defiant said:
The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F), or , air conditioning is selected and battery temperature sensor is above 41° C (106°F). It will then de-energize when , air conditioning is selected and coolant temperature is below 92° C (198° F), or , air conditioning is selected and battery temperature is below 38° C (100° F).

Does not solely depend on whether the AC is turned on.

Sorry, I'm not sure where the coolant temperature is measured.
I am assuming that is what you meant(?) since the thermostat in the jeep is inline with the lower radiator hose.

uss2defiant · May 5, 2015

Karaus said:
On the 2 wires coming off the relay to the radiator fan im reading 12.6V on one wire, and 5.7V on the other wire?

One should be battery positive and one should be ground.
Not sure why you're reading a floating voltage.
Are you reading both pins with respect to ground?

uss2defiant · May 5, 2015

Karaus said:
yes i have a clutch fan.

your jeep shouldn't overheat with only the clutch fan. I don't know how long my wife (fiance at the time) had the jeep with the e-rad fan not working.

The only thing that would be affected would be the AC which you already bypassed so it wouldn't make much of a difference.

twowings · May 5, 2015

Would a wiring diagram help?

Karaus · May 5, 2015

It is right below the intake slightly off to the left side of the alternator if your facing the front of the motor. The dealer called it the thermostat sensor. This sensor then goes to the relay. It also controls the gauge inside of the vehicle.

I wish i could find the the ohm spec of this sensor to see if its fully functional. May just buy a new one and see if that fixes it. It may be getting stuck at 50% closed causing the gauge to only read half. The ohms start at 2.000 then as the vehicle gets to operating tempeture it steadly drops to .900ohm then stops dropping.

Karaus · May 5, 2015

im reading battery positive on one wire at a time then the other lead to battery ground. The floating voltage is odd. Not sure what is causing that.

I would think the clutch fan would do the job, but pulling my pop up camper on a hot day could be too much of a task. I had the transmission go out 20,000 miles ago and we installed a large external transmission cooler in between the radiator and condensor. the fan would be a nice backup.

I think i will just wire a switch and leave the rest of the wiring as is. That way it will come on when suppose to if its still working. Thank you for that link.

renegade 04 · May 5, 2015

What I mean is the relay has constant positive power and the relay is controlled using the ground wire not positive like we normally would think.

uss2defiant · May 5, 2015

2002 fsm can be found here
Index of /manuals/Jeep/KJ

uss2defiant · May 5, 2015

do a instrument cluster test to see whether that temp gauge is working

https://www.youtube.com/watch?v=U4tgVYtyr9M

uss2defiant · May 5, 2015

renegade 04 said:
yup that is the link I used but when wiring it for the libby people need to remember that the libby turns the fan relays by opening a path to ground and not by applying positive power to the relays.

That's for the dual fan speed and not the single speed on our 02s and 03s.

Karaus · May 5, 2015

Thanks everybody for the help! Found the problem or atleast the cause of it. I replaced the coolant temp sensor and now it's working

HELP! Fan Relay

New Member

Full Access Member

Full Access Member

New Member

Full Access Member

Full Access Member

Full Access Member

Full Access Member

New Member

Full Access Member

Full Access Member

Full Access Member

Full Access Member

New Member

New Member

Full Access Member

Full Access Member

Full Access Member

Full Access Member

New Member

Similar threads