# Jeep Cherokee Cooling Fan Doesn't Run



## RandySaint

I have a 1993 Jeep Cherokee 6 Cyl that is not getting any power to the electrical cooling fan. I hooked up a volt meter to the connector and I get no voltage when the car is running A/C on or off, nor when the car gets hot.
I've checked all the fuses and they are good. I've swapped the relays so they don't appear to be the problem.

Would you have any suggestions on what to do next?

Thanks in advance,
Randy


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## Volt-Schwibe

you say you swapped the relays, does that include the one at the bottom of the radiator that is temp regulated?

this could become a serious problem if you drive it.

i would like to help you resolve this as soon as possible.


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## Volt-Schwibe

here is a diagram of what you should basically be encountering.

keep in mind, this is a basic illustration of a typical AMC cooling fan wiring diagram.

i drew this up using other jeep wiring diagrams as a reference, and it seems that they all follow this pattern, even though the parts are sometimes located in different places.

but it all boils down to this.

the big red fat wire has a fusible link on it, and is the most probable cause of this fan simply not running. a fusible link is only a few bucks, and on your year, it should be connected to a small junction block near the drivers fenderwell.


this might help.


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## RandySaint

Thanks for your help, but I'm still not finding it.

The wire that powers the fan motor is green and is connected to the fuse box that's under the hood (which also houses the relays).
I've checked continuity on the green wire and it is fine all the way back to the relay. I've swapped the relay with the starter relay (which I know works) and am still having no power for the fan.

I've attached a couple of photos. The one of the passenger side, shows the battery, and where the fat red wire comes off the positive terminal (red arrow). That wire connects to the fuse box (green arrow). I didn't see a fusible link in that wire, and I would expect if that's where it is, I wouldn't have power for anything. 

The other photo is the drivers side, where I tried to find something that I could identify as "a small junction block near the drivers fenderwell". In the photo, there's a 1.1 Ohm ceramic resistor (green arrow) that tests good. There's a bunch of wires that go into a box near the front (yellow arrow), but I'm thinking this might be the electronic control. Also, there's a bunch of wires that go down to the back side of the under-dash fusebox (red arrow). Included in these wires is a fat red one, but I don't really have access to it to see if there's some type of fusible link on it.

For that matter, I'm not even sure what a fusible link would look like. I assumed it would look like a cylinder in line with the wire that could be separated to pull out a fuse from within. However, the Haynes book says "Fusible links cannot be repaired, but a new link of the same size wire can be put in its place." Where then it talks about how to solder a new one in place. 

Any help you could give me would be greatly appreciated.
Thanks!


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## Volt-Schwibe

yes, fusible links must be replaced.

basically, think of a fusible link as the "weakest link". they make the wiring system, they calculate in all the fuses, and then they take the spot closest to the starter or battery, (some juntion at the starter) and add in a short segment of smaller wire. this is done so that if it were to overload, the failure will happen exactly where they wanted it to.

they are about 8 bucks, and you crimp them in place, and then solder them, and wrap them as waterproof as possible.

i will try to find a picture of one, but it doesn't look much like a fuse.

be back in a few minutes.

here is a link to a decent explaination and a picture. http://www.autoshop101.com/trainmodules/circuitprotection/118.html

ok, what i was meaning about junction blocks may not apply to your model of jeep. many of them use the positive lug on the starter, and some use a part like in this picture, it simply attaches to the firewall somewhere, and all the main power leads attach to it.

sometimes, like in a ford, the starter solenoid is on the firewall, and they use that as the junction.


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## Volt-Schwibe

P.S., i have noticed your post on the jeep forums, and it doesn't look like you are getting any bites.

i'm going to make a phone call, and try to get a diagram of your vehicle emailed or faxed to me.


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## JamesO

Here is a specific link on the Jeep fusable link:

http://www.autozone.com/servlet/UiB..._us/0900823d/80/15/3e/6c/0900823d80153e6c.jsp

The ceramic thing on the drivers side with the green arrow in your picture is the ignition system ballast resistor. Nothing to do with the cooling fan.

Check this link for the wiring diagram:

http://www.autozone.com/servlet/UiB..._us/0900823d/80/15/3e/8f/0900823d80153e8f.jsp

I was not able to find the specific diagram and did not know the engine size, from the picture it appeared to be a 4cyl? Seems they leave out the cooling fan circuit, just the feed from the ECM to the cooling fan relay is what I found.

Do not rule out the ground side of the circuit!

Have you tried to bypass the fan control circuitry and hot wire if from the relay location to make sure the wiring from the relay location and the fan actually works. Should be able to do this by pulling the relay. Be careful not to backfeed any of the circuitry and make sure you use a fused sorce in case something is shorted.

Also keep in mind testing with a Voltmeter can be misleading. There may be a bad connection that shows Voltage, but will not pass enough current to operate the device further down the line. Test lights tend to be a better test tool in the automotive world.

JamesO


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## Volt-Schwibe

nice work james, those seem like perfect links.


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## james robinson

I see it suggested that you that you bypass(hot wire) this . I would say it may be a good thing .To put an inline fuse in any peace of wire I was using this way. Not knowing this perticular system . There is normaly a plug in the radiator with two wires to it if you joined the two wires (with a fuse) put the spade conectors onto the fuse .That would eliminate the switch in the radiator as a problem. It leaves the fan running all the time ,and should only be used as a get you to the nearest switch supplier. For some reason I had to do this with afew cars i had .Hope this makes some sence and helps.


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## Volt-Schwibe

heh, i used this method once too....

although not exactly like this, it wasn't a radiator.

i might add, that with the relay, that switch should only need a 5 amp fuse at most.


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## woodnymf333

*overheating '89 cherokee 4.0 I6*

I've a similar overheating problem but those diagrams don't match what I'm seeing under the hood. I've tested the cooling fan by hotwiring to the battery and it runs. I've tested the temp sensor at the left top of the block while the engine was cold with an ohm meter and got 700 ohms. The chilton I have says that the sensor should be over 1000 but I figure lower the resistance the better right? So i figure the sensor is good.

How do I test the cooling fan relay? There are two wires coming out of the cooling fan, black and red/black, and this goes to a relay on the left engine wall but I don't know which how to hotwire it. I can't find the ECU either. Help!


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## larcou

*thermo switch*



woodnymf333 said:


> I've a similar overheating problem but those diagrams don't match what I'm seeing under the hood. I've tested the cooling fan by hotwiring to the battery and it runs. I've tested the temp sensor at the left top of the block while the engine was cold with an ohm meter and got 700 ohms. The chilton I have says that the sensor should be over 1000 but I figure lower the resistance the better right? So i figure the sensor is good.
> 
> How do I test the cooling fan relay? There are two wires coming out of the cooling fan, black and red/black, and this goes to a relay on the left engine wall but I don't know which how to hotwire it. I can't find the ECU either. Help!


well read all the info and traced my problem to the thermo switch in the radiator..not sure what temp it is supposed to close but doesn't seem to want to..so i jumpered the two wires leading to the relay and it will work with ignition on for now..hot here so cooling is most important..thanks for all the clues..


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## valeriej

Jeep Cherokee Sport 2000:

I'm having cooling fan issues, too, though the fan works on high but not on the lower settings. There's plenty of freon (we recharged). Running the fan on high all the time seems to overheat everything. So . . . AC is basically on the fritz and now my power windows aren't working, stuck in the closed position. It's starting to get warm and I'm getting no air . . . 

1. My haynes manual says to do several things, including checking the fuse (no diagram for the panel on the panel door OR in my owner's manual) or circuit breaker
2. Inspect actuating switches for broken wires and/or loose connections
3. Remove inside door panel and check wires there, also glass for binding

I'm planning to do #'s 1 & 3, if I can find a diagram to the fuses.

My dealership service department says it sounds like the regulator in the door . . . to the tune of $237 for the part and whatever for the labor. I really think this is electrical, as it affects ALL windows and my power sideview mirrors. 

I'm going to cross-post this to another message about the windows . . . since I covered two issues in this post. This is my first time here--I'm a 50-year old very active, usually competent do-it-yourself-er on minor car things and around the house. 

THanks,

Valerie


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