I think my aux electric cooling fan may not be working. As I am a neophyte trainee in the realm of Jaguar systems I wanted to be sure I understand how it works.

From looking at the electrical guide it seems that a thermal switch forces a relay to close/open at certain temperatures which in turn starts/stops the fan. It appears that this is the only control of the fan operation?

My understanding is that the thermal switch is located in the top left hand side of the radiator, is that correct? Can I access it without moving the air box?

I have already confirmed that the fuse and relay are working. My plan now is to first jump pins 30 and 87 of the aux cooling fan relay and see if the fan comes on. If the fan doesn't come on, I'll check the wiring to the fan from the relay and if that is ok, I will assume the fan motor is bad and will replace it.

If the fan does operate, I'll work the other way and check the wiring to the thermal switch and the switch itself.

Does all that make sense or am I missing something?

Also does anyone know what temps the switch should turn on and off?

Many thanks,

Allan

 

Hi Allen,
Makes perfect sense in what you are proposing to do.
Before putting a supply onto the motor, check the resistance of the motor with a meter. This will also give you an idea of whether the motor is good or not.

 

Well the fan works when I jump the relay. I will try and get the engine good and hot and check the temp with an IR thermometer. Does anyone know what temp the switch should activate? I'm guessing the switch may have gone kaput but I'll check the wiring too.

I can see the switch behind the air box so I'll have to remove it. One thing I did notice, the wires coming out of the switch are white and white with blue rings. The wiring diagram calls for a white and a green/brown. The diagram does not show a connector or splice between the switch and the relay but I must have one because the wire going into the relay is a different colour. Is that usual? I'll check but perhaps the connection is bad?

Allan

 

I don't know. It's was set for 94ºC on (at least some of) the older models. It's not unusual for temp switches of various sorts to have the rating stamped into the part itself, somewhere. Might not be easy to read, though. Worth a peek.




Cheers
DD

 

Hmmmm, well I'm not sure yet if I even have a problem!! I drove the car around for about an hour to get it good and warmed up. Temp needle of the dash is right on N. Actual measurement of the radiator top hose shows a temp of 196.6F which seems quite normal. Here is a pic cruising along.



I then did everything I could to get the radiator coolant hot enough to to initiate the thermal switch. The trouble is I could only get the temp up to 204F and the needle shows a good bit past N but still well within the N range.
Here is a pic at the highest readout.



Doug mentioned that the switch was thought to come on at about 201F but I would think that 204 would be within the wiggle room?

The outdoor temp is only 80F today so maybe I'll wait for a hotter day but for now I'm not sure if the switch is working or not.

It is interesting though that there are many posts regarding high readings of the temp gauge, I'm wondering if that really is no problem at all and why Jag changed the N mark to a wide range?

What do you think?

Cheers,

Allan

 

@Allan

As a V12 owner, I am an avid temperature gauge watcher, so I understand how you may feel uncomfortable about the gauge. The reality is I think the temps you are recording with the IR gun are fine, meaning the car isn't running too hot currently. You mentioned you jumped the fan at the relay, which is a good way to rule out certain pieces of the system from malfunction, but if you jump the switch itself on the side of the radiator, then you rule out absolutely everything apart from the switch.

Here's what I would do next........ get the car as hot as you can (so the temp gauge looks like it does in the second pic, then jump the fan (either at the switch or as you did last time at the relay... for this test it doesn't matter how you do it, you just need to get the fan running). Leave the fan running and watch what happens to the temp gauge and at the same time check your IR readings...... my gut feeling tells me when the fan starts running the temp gauge is going to move cooler, and your IR readings should follow that.

Post back how that goes......

I had a quick look for a fan switch online for the 4.0 cars and it appears to be out of stock and on back order, but I didn't look really, really hard.

On my car I replaced the temp switch with one rated at a lower temperature, so my fan comes on at 84 and goes off at 77. Maybe someone knows if this is available for the 4.0 cars....... In normal cruising conditions my fan doesn't run, but when stopped in traffic, or under heavy load, the fan comes on..... the gauge then drops, then the fan goes off again. This cycling then continues. I have rigged an idiot light in the cabin so I know when the fan is running. For me, I'm not too interested in where the needle on the gauge is pointed because I know the gauges are quite flaky, but the main thing that keeps me sane is seeing the gauge get cooler when the fan comes on.

 

@Sarc,

I'm following you and jumping at the switch would certainly prove the wiring to the relay is good. However, I'm not sure that would necessarily prove the switch is bad as I can only get the temp up to about 204F at the moment. If I could get the temp up to say 208-210 without the fan kicking on, then I would say the switch is probably bad and replace it. I'm quite confident that if the fan kicks on the temp will drop somewhat but like you I just want to know when and how much

I like your idea of getting a switch that kicks on a tad earlier, although I'm quite comfortable at the range I'm at right now. I just would like to prove to myself whether or not the switch actually works

I'll keep you posted as to my findings.

Cheers,

Allan

 

This isn't convenient, but it would do the trick

Remove the switch and suspend it in a pan of water on the stove....of course you want only the probe part in the water.

Attach an ohm meter or simple self-powered continuity checker across the terminals

Turn up the heat. Use a thermometer to monitor temp.

Your ohm meter will show zero resistance, or your continuity tester will glow, when the switch closes.

Cheers
DD

 

Heh heh, right you are Doug, that would certainly do the trick

I was just hoping for the easy way out by getting the engine coolant hot enough. It should be warmer tomorrow I will try again.

 

I personally would rather try the "pan" method or just replace the switch altogether if I suspected something before I tried to get my V-12 "really hot" or "as hot as you can" as a means of trouble shooting...one minuet your out a temp switch and the next your pulling a head for a dropped valve seat. Heat cycling is not something these engines are known to tolerate well. "Keep your cool" (pun intended ) and just check the switch outside of the car as Doug described.

 

Does your fan turn on when the AC is on? Because my Aux fan only comes on when the AC is turned on. I have never seen nor heard my auxiliary fan run when the AC is off and with the gauge this high.

My mechanic confirmed that the fan will turn on when the AC is off if the temperature trips the sensor. He tested by applying a heat gun on the temperature sensor.

 

For my car (1994 4.0L AJ6), the fan activation is ONLY controlled by the thermostatic switch in the radiator and the cooling fan relay, as you can see below. The A/C on/off has no bearing on it.



Cheers,

Allan

 

Smart mechanic! So long as you don't go hot enough to melt any wire covers!

 

Good evening,


I'm facing the same issues with my 96. Did you ever resolve yours? Did you verify that the switch on the radiator with the white/blue wires was really the radiator thermal switch? My manual says the switch is located on the water pump inlet but I can't see anything there. I'm also skeptical because the wiring diagram shows a green/brown wire leading from the relay to the switch. I've very confused by all of this and would really like to know what you finally found out/did.


thanks, Mitch

 

i see that in the pictures the highest temp is with the speedo bottomed out but it was at the N at 50 mph. Definitely indicative of a aux fan.

Honestly my temp switch went out and I just straight wired it to come on with my ignition. Sure it means my fans life will be half as long, but its like a 30 dollar electric fan off ebay, not a big deal and works better for me (as a student) than a 70 dollar temp switch and the original POS they call a fan.

 

Allan,

See my latest reply to Fesiwig today on the same subject:

https://www.jaguarforums.com/forum/x...73/#post973245

Don't worry about the white and white / blue wires. They change at the next junction plug to black and green/brown.

Switch still available from Jaguar.

Cheers

Paul

 

Cheers Paul,

I actually sorted through the whole mystery of the fan switch and posted what I think is the definitive answer in this post https://www.jaguarforums.com/forum/x...-answer-98660/

I'm glad the switch is now available again, when I had checked with Jaguar last year it was NLA. It is quite rare that these switches go bad. Many owners replace them because they do not turn the aux fan on until the temps are quite high but this is normal and as designed by Jaguar. The temp needle on 94MY cars will get to about halfway between N and H before it kicks on as in this pic.

 

There's also a mod that will turn on the aux fan anytime you turn the A/C on. I did that on my car and I am quite happy with the results.

If you need to get the car hot, make sure to run the A/C while doing everything else you did.

 

There are Thermo switches that will turn the electric fan on at a cooler temperatures. I removed my original 85C temp switch and replaced with a 82C switch. Just do a google search and you will find all the info that you need...

 

Yep, as I pointed out in the thread, just about any M22 x 1.5 threaded switch will do but my interest was to understand how the system was designed to work and why. Then it was easy to decide what I wanted to do