splouie

Hi,

So this 2000 Grand Cherokee 4.0 is notorious for having a cooling fan issue. Had it 10 years ago, and have it again. The electric cooling fan wont turn on anymore at 210 please help, and than overheats at low speed unless I drive faster to move the air.

I changed the radiator cooling fan relay
I changed the fuse in the box in the hood.
I jumped the fan to another battery and it spins
Have no engine codes

Have not changed the coolant temperature sensor, but there is no code for it.. any thoughts on why this fan wont turn on.. the only thing left is wiring and cant beleive that would ever break..

dave1123

Welcome to CF!

The cooling fan relay is controlled by a low voltage signal from the PCM. Check that there is no corrosion in the plug or wiring. It's only a pulsing 5V signal on low speed or a steady 5V on high.

OR.....You can just hot wire it. You could put a temp sensor in a sleeve in the upper rad hose and a separate relay to control it. There are several write-ups on the forum for this.

splouie

Ok so assume its not getting the voltage.. How can i test that.. I have not used a test light in 25 years... and dont want to short things out.. if i remember.... negative side of test light to metal on the car, turn the ignition key to on, and than touch the test light to the positive prong on the relay harness? is that correct... if thats the issue, what would cause the low voltage other than corroded wiring and how to fix that the right way so it gets voltage? thanks

dave1123

No, unfortunately that circuit is only hot with 5 volts WHEN THE ENGINE IS HOT in excess of 210*. You can only read it with an analog voltmeter. If it's in pulse mode, a digital won't follow the changes quickly enough. That's why the dealer gets the big bucks to play with it. They have a specialized scan tool for this. I'm not even sure which terminal it is on the connector. This is a RELAY circuit that switches on the fan with 12V when the relay is activated by a 5V signal from the PCM.

As I said before, you could hot wire it to a toggle switch temporarily so you can drive it while you figure it out. You could also mount a clutch fan in place of the electrical one but you'll need the shroud from a ZJ as well. The water pump hub will except the clutch fan mounting bolts. The reason they went to an electric fan was to regain the parasitic hp loss of driving the cooling fan.

The only way to test the continuity of the wiring is by disconnecting the harness at BOTH ends and finding which pins are connected and IF they are.

splouie

I think i am going to get the harness for the cooling fan relay, i here the plug breaks all the time causing the voltage issue u describe... have you seen a coolant temperature sensor go without an engine code?

dave1123

I've never seen it pop a code, but I have seen it in the VIC.

maxxtreme

Hi everyone, in my little experience, i had this trouble with a WJ i used to have, and i just replaced the electric fan with a fan clutch and vent from a dodge dakota and no more hot engine even with 101° F. cheers!

dave1123

Thanks! That's just what we need, someone who's done it already. If it ever happens to mine, that's exactly what I'll do. If it's not enough, I'd put a small booster fan in front of the A/C condenser.