ruglyot

Good day!

After being a ***** wagon man for years, working 20 years as a Jeep/ GM parts manager (and another 8 years with NAPA - and currently working there), I finally decided I needed something more highway friendly and decided a Cherokee was the obvious choice as I progress into the current age with Jeep.

So I just picked up what is titled as a 90 XJ, but seems to have some 91 wiring similarities. The man I bought it from did replace a door and fenders and the radiator came from an auto trans vehicle. All this is fine - $1500 for a 4.0, MT, A/C, 4" lift and 100 thousand miles is perfect for an off road rig for me(to start with!).

My immediate problem is the engine cooling fan had the wires cut 6" past the plug. Tracing the cooling fan socket from the #87 terminal on the fan relay led me to a green wire under the ECU that is about a 20 gauge and the black wire next to it, and cut to the same length, is also the same gauge ( and is indeed a ground). The problem I see is the wires from the fan motor are about a 14 ga. (and different colors - light blue and black). Is there something missing or was this the way Chrysler did it?

I appreciate any input you can give me - thanks! Russ

Willys55

Maybe this will help.......

ruglyot

Yeah, that's the same one we have on our NAPA cataloging system. I'm quite sure that I have the circuit pinpointed, but the idea of the harness going from 20 ga. to 14 ga. seems idiotic - a resistor effect and definite spot for wires to heat up. I haven't opened up the loom yet, it looks so nice all taped up and such, but I'm inclined to trace back and rewire with 14 ga.. I do get inclined to "over engineer" some times, though. The wiring out of the relay center didn't seem to have any 20 ga. wiring out of it, so it seem like it "necked-down" somewhere in the harness. Any ideas why? Does your harness have the same gauge wire back as far as you can see? Russ

ruglyot

And that diagram was listed for the 90, and mine seems to be the 91 layout with the relay in a relay center on right fender well. I'm wondering if it was a 91 with the dash(and VIN) changed from donor 90. ? Russ

Willys55

Russ are you sure the relay that you traced back is for the fan? I also know that you go up in gauge but never down on gauge. Russ


P.S. my name is also Russ..........LOL

ruglyot

I think the only way I'll know for sure is to open up the loom and trace it by eye, but it was the relay marked "cooling fan" in the relay center, and with relay unplugged and ohmeter connected to socket for #87 terminal and end of cut green wire under ECU, it showed continuity. Russ

Willys55

If it is the 91 system, then the pcm provides the ground for the cooling fan relay. Have you tested to see if the ground is provided to the relay? You mave have to turn the a/c on and set to max cool to test. If it does, then I would run the cooling fan power using 14 guage right up to the relay center, just upgrade the push pin in the relay center.

Willys55

jump a wire from battery supply to pin 87 and test the other end(green wire) for matching battery voltage

ruglyot

Yeah, good point on the power jumper idea, but no, I haven"t verified switching signal from ECU. I just found the the ohmeter verification a little bit ago as it was getting dark, and time to put kids to bed, and on ad on. So, I'll have to do more checking tomorrow. I did see one reference in a "component part locator" on Mitchell that showed the diode out in that area, which only raises more question re: gauge size. A sample '90 and '91 engine bay side by side would be ideal but have yet to find either here in town (yet...). I'm leaning to splitting the loom open so Ill know for sure. Russ

ruglyot

Well, I finally found the time - warmer temps here pretty much forced my hand-to get in depth with the wiring and I did find that the wire gauge from the relay to the fan is indeed 18 ga. The cooling fan and radiator, condensor had been replace from a donor that was running R134 and an auto trans, so it seems newer models must have upgraded the wire gauge.

So, with that knowledge in hand I attached plug, rewrapped wires and then found out the cooling fan is junk! Oh well, the next investment...P/N 52005748! Russ

ruglyot

I found out that the cooling fan on my Cherokee is the 97/- 10-blade unit (not 52005748) and ordered one from the NAPA warehouse in SLC, but ordered too late in the day - so it didn't come in today! So with nothing to loose and a hot weekend ahead, I pulled my old motor off the shroud and found it packed with dirt enough it wouldn't even turn. By bending the tabs that hold the back cover on, the cover came apart easily exposing the brush plate (also easily removed) with good brushes and filthy commutator. I lubed the front bearing/bushing with Power Lube, grease in the back bushing, Scotch-brite cleaned the commutator and a thorough blast of air to remove all the black dirt. Reassembled and yes - it works great! I'll probably keep the new fan in stock for awhile till I'm sure the repair is good. An easy repair and the brushes look easily replaceable if needed. The fold over tabs on the rear cover probably won't take too many repairs without breaking but the other areas of the rim could be bent over at that point. So, before condemning your old one, it might be worth taking apart! Russ