1994 XJ6: Cooling Fans Not Working

I’m having one issue after the other in trying to get the car back on the road.
It has been about 4 years since I last drove the car due to fuel system contamination.
And those 4 years of sitting up has consequences.

The cooling fans do not work at all. I have found out that there is
no power anywhere in the cooling fan circuit. There’s no power to
the big green relay plug, no power to the thermal switch on the bottom
of the radiator.

I have also found that the thermal switch is corroded as well as the thermal
switch plug. So i will be replacing the switch and hopefully the plug can be cleaned.

Can someone who is familiar with this problem on the 94 cars point me in the right direction
for a fix.

I forgot to mention I have checked the two cooling fan fuses on the driver side fuse panel and they are good. I have two cooling fan relay modules but with no power to the relay base haven’t been able to test them for proper operation. What could be causing the loss of power.

Although you have checked the relevant fuses have you checked that they have power? The fuse boxes sometime develop dry joints and fail to flow power through the fuse.

I have checked and they are getting power but I do not know if they are in fact distributing power. I do not know how to check for that…if you could advise me that would be great.

Also, I looked at the car again this morning and checking the connectors; I found that the plug for the thermo switch is corroded from the harness. When I grabbed it it just came apart in my hand. Im now trying to source a plug and I have ordered a new thermo switch.

I have an extra, working set I bought for my car that if you want them I’ll make you a deal.


can you clarify what the working set is…thanks

Cha Cha …

One quick tip on troubleshooting your fuse boxes.

Take your multimeter (you must have a multimeter if you own this car) and place the black lead to a good ground and probe the two receivers that the fuse plugs into with the red lead. One of them should give you 12v (make sure the ignition key is in position 2). That will tell you if power is flowing to the fuse. If it fails this test almost certainly the problem is in the fuse box.

If it passes now test the continuity from the other fuse pin to the first relay in the circuit. You may need a long jumper wire depending where the relay is. Remember now we are testing for continuity not voltage. If it passes this test the fuse box (at least the circuit that you just check) is OK.

The above is just a generic relay with the points to be tested.

Ok, I just reread my post and an even easier why to eliminate the fuse box as a problem with the circuit would be to simply turn on the ignition and probing the relay with the red lead on pin 87 and the black lead on pin 86 or any good ground. You’re checking for 12v. Sorry if I confused you.

just making sure we are on the same page: I need to test the fuse box even though according to the fuse it is getting power. Also, if I am correct the first relay in the cooling circuit is the big green relay correct.

also I could just the check the relay socket for continuity as there is no pin 87 on the cooling fan relay. Please advise and thanks for the help

With these fuse boxes, the fuse will show good at both sides, in and out.
In my experiece, the problem is usually after the fuse, i.e. getting the 12v OUT of the fuse box and into the wire.

ok…please excuse what maybe simple questions and procedures to some but im new to diagnosing electrical issues on cars even though I have a good working knowledge of residential electricity.

So by testing the actual slot that the fuse plugs into this will tell me if there is power actually leaving the fuse box. so Im guessing these fuse boxes in the back are just like plug n play sockets in that the wiring harness plugs into the back of the fuse box. Is that correct.

No, not exactly. Yes a harness plugs into the back. Between the fuse and the plug there are two circuit boards and many solder joints. These solder joints can crack due to the flexing of the circuit boards and can also corrode due to water ingress.
Common treatment is to remove fuse box and re-flow the solder joints.

Cooling fans for a 1994 XJ12

ok…not sure if i need them yet. still waiting on parts. I will definitely get back with you if the fans are shot

They are radiator cooling fans for a 94 XJ12 I bought and ended up not needing. Will fit 6 cyl. or V12 car