Cooling Fan Relay

[Graboon]

I bought a 1991 Cherokee 4.0L and suffer the same overheating problems found in various other threads here. One of the troubleshooting tips in the shop manual I bought says to check the cooling fan by connecting it directly to the battery. I tested it and the fan worked! I had NEVER heard this thing move before. When trying to figure out why this fan doesn't turn on when needed, I noticed that the spot for the Colling Fan Relay in the fuse/relay compartment (under hood) was empty.

Can someone tell me if my relay is missing, or is there not supposed to be one there?

Thanks

/\/\...

[Dale Aeppli]

Originally Posted by Graboon

I bought a 1991 Cherokee 4.0L and suffer the same overheating problems found in various other threads here. One of the troubleshooting tips in the shop manual I bought says to check the cooling fan by connecting it directly to the battery. I tested it and the fan worked! I had NEVER heard this thing move before. When trying to figure out why this fan doesn't turn on when needed, I noticed that the spot for the Colling Fan Relay in the fuse/relay compartment (under hood) was empty.

Can someone tell me if my relay is missing, or is there not supposed to be one there?

Thanks

/\/\...

HI TAKE ONE OF THE OTHER RELAYS AND PUT IT IN SEE IF THAT WORKS THE REYAYS ARE ALL THE SAME NAPA SELLS THEM $8 DALE
[email protected]

[Graboon]

Thanks Dale - I'll pick one up to test it out.

Still- I'm curious to know if there was ever a relay in that spot. If so, I wonder why the previous owner took it out without replacing it!?!?

[Dale Aeppli]

Originally Posted by Graboon

Thanks Dale - I'll pick one up to test it out.

Still- I'm curious to know if there was ever a relay in that spot. If so, I wonder why the previous owner took it out without replacing it!?!?

IF YOU LOOK UNDER THE LID IT TELLS WHERE AND WHAT RELAYS ARE FOR THAT CARS EQUIPMENT DALE [email protected]

[jeep!_r]

Under all the cherokees hoods I've owned, all my relays were a;lways there. Try turning the AC controlls to AC and see if the fan comes on. If not, put another relay in the empty spaces spot and try it again. If it works, then theres your problem. Fan is suppose to come on when AC is on, and when the temperature of the coolant reaches above 212. If it works both times(test above), then chances are you have a bad coolant temp. fan switch. Test this by jumping across the two wires(in the same fan plug oppose the fan....red and black wires I belive). when jeep is above temp, or remove and put in a pot of boiling water, and watch the temp. Hook an ohmeter up to the switch and see if it makes contact above temp.
B

[Graboon]

Originally Posted by jeep!_r

Under all the cherokees hoods I've owned, all my relays were a;lways there. Try turning the AC controlls to AC and see if the fan comes on.

Unfortunately, my Jeep is not equipped with A/C
I've phoned both Napa Auto Parts and Canadian Tire -- They couldn't even find the part number in the computer inventory. One guy told me there is probably no relay needed, just temp sensor switch. I found it strange that Jeep would have a spot for the relay if they didn't need it. Perhaps it is only meant for Jeep's with A/C?

I'm considering buying a regular on/off switch and manually controlling the fan. Any tips on how to do this right?

Cheers

[jeep!_r]

That's why you're missing a relay then. If you don't have AC, then there wouldn't be a need for an ac relay! Anyhow, chances are almost 100% that it would be your temp fan control switch. To test it, get your jeep hotter than 212, and see if the fan comes on. If not, unplug the switch(drivers side of rad, by the lower rad hose), and put a jumper across the plug that does not go to the switch(black and red wires), and see if the fan comes on. If so the switch is your problem. You can be sure by boiling water hot enough, and seeing if the switch makes contact above 212(on the stove). I would say its your switch as they have been known for going out. I myself would find a good working switch(stove test), and just keep it original. But if you must putting a switch in would be easy. Cut the wires on the switch side(so you can use the plug), and run the two wires back to the dash, and put a switch in. Piece of cake. Whats your jeeps problem?? Is it always overheating??? What kind of weather are you driving in(temp), and what sort of conditions(stop and go???). Theres a chance if the weather is cooler out, then your thermostat might be sticky or not working well. I ran my jeep through las vegas a couple of weeks back when it was 112, and it ran warmer than usual, but never overheated, that was with a factory 195 thermostat. If you live in warmer climates, you can go away from OE and getting something liek a 170 or 180, which would greatly help. If you live in a colder climate though(like montana), then you might wanna switch it back to factory during the winter. Email me directly if you have anymore Q's
B
Bozeman, Montana

[Saudade]

Echo what Jeep!_r said about the switch going out but first verify that your coolant level is correct in the bottle. Then, when engine idles, you should see coolant circulating back into the coolant bottle. If you see nothing until you rev the engine, your coolant level is low. Slowly add until level is corrected.

Test it first by jumping across the fan side of the connector and see if the fan starts. You can do this with the engine off but key on. Then connect an ohm meter across the switch side. It should read as an open circuit (infinite resistance). Then start the car, let it idle and get hot (do not race the engine). Once it reaches around the middle of the temp gage the ohm meter should register low resistance showing conectivity across the terminals. If nothing, keep idling and let it get hotter but DO NOT LET it overheat. Still nothing, then your switch is bad.

I had to replace mine. Cost $30 new from a local Jeep dealer. Removing the electric fan gives you enough access to the switch. However, coolant will rush out so be ready with the drain pan. Add coolant back to proper levels and test again.