Bypassing factory Electric Fan

I've done a lot of research lately on the electric fan on my 2001. I've seen quite a few write ups on adding a manual switch to the wiring to control it. I can't get the fan to kick on for the life of me, AC and enough pressure it does not turn on. I can't get it hot enough to test it either.



What I would like to do instead of having a manual switch is a separate thermostat switch, either a probe style or one added to the radiator hose to kick on and off the electric fan sooner than the 212 degree or whatever it is it comes on now.


I've tried this with a probe style switch (where the manual switch would go in the diagram) but got a CEL and the fan never turned on.
https://www.cherokeeforum.com/f51/right-way-install-manual-switch-your-e-fan-212243/



My next step would be to bypass the entire factory harness adding a separate relay and thermostat switch connected to the factory fan. Is this possible to do without getting a CEL. There must be a way to tricking the computer into thinking the fan is still connected?

Can't you just unplug the fan to see if you get a cel light.

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The best way to avoid all the issue is to have the PCM re-programmed for the new temp setting. That's what I had done for my 2000 stroker.

RCP Phx said:

The best way to avoid all the issue is to have the PCM re-programmed for the new temp setting. That's what I had done for my 2000 stroker.

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The dealership can do this? Was not aware of that. I knew they could possibly reprogram it to come on with the AC like the 99 and downs

Evan03 said:

Can't you just unplug the fan to see if you get a cel light.

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It does trip the CEL.

A dealership "should" but there are only a hand-full that do custom tuning in the US.

Fans draw a ton of amperage on start up... first things first, have you checked fuse and relay? Put 12V directly to the fan?

I added a thermal switch to my radiator. 1/4” NPT I think, or 1/8” NPT. From Summit. I spliced in to the switched ground for the fan relay. So, the ECU signal should still work if the thermal switch fails-open.

Drivetrain is 1994 and I am not sure if there is a factory application for the radiator.

Next weekend is the trial run.

RynoMJ said:

..... I can't get the fan to kick on for the life of me, AC and enough pressure it does not turn on. I can't get it hot enough to test it either.

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For 1997-2001 OBD-II to test the e-fan circuit, unplug the wire connector from the Coolant Temperature Sensor on the thermostat housing The fan should start in 5-10 seconds and the Check Engine Light should turn ON.

RCP Phx said:

A dealership "should" but there are only a hand-full that do custom tuning in the US.

Click to expand...

Yea I doubt the one by me will.

Tim_MN said:

For 1997-2001 OBD-II to test the e-fan circuit, unplug the wire connector from the Coolant Temperature Sensor on the thermostat housing The fan should start in 5-10 seconds and the Check Engine Light should turn ON.

Click to expand...

I’ll have to try this when I get home.

VAhasnoWAVES said:

Fans draw a ton of amperage on start up... first things first, have you checked fuse and relay? Put 12V directly to the fan?

Click to expand...

Yep fan works with 12v directly to it

I wire tapped into the positive side of the efan and ran it to pos battery. I've been manually operating it like this for nine months. No issues. If you want automatic, then run appropriate gauge wiring from the battery along a fuse and thermal switch. Probably want to add a relay to engine-on, so it only runs while the key is in on position.

But a RCP Phx said, getting the ECU reprogrammed is less work, but it will be more money.

I did the same thing that RCP Phx did. My e fan turns on at a much lower temperature now after I got my stroker tuned by Chris Jensen. [email protected].

The 00-01 JTEC+ is hard to fool, it would be nice if someone made a "Fan Simulator" like I had to but for my MSD ignition.