Hi all I need some help.
I have a 3.2 1997 x300 and I have an issue that I just can’t not get my head around. I’ve only had the car for a few weeks so I am still learning here.
The issues is the water temperature gauge. On the drive way or in heavy slow traffic the water gauge reaches the normal mark ( half way point on the scale) when I get going and at any speed over 50mph the needle will full and sit in the blue cold section and if I slow down it moves back to the normal mark. The hot air coming out the vents will mirror the gauge. When the gauge is low and reading cold the air from the vent goes cold and so on. This points to a stuck open thermostat but I have now fitted three new ones and placed the vent hole at the 12 o’clock position but it’s not helped or changed this issue. Now both the upper and lower radiator hoses get nice and hot so I’m guessing it’s not a thermostat issue?
I have tested all three thermostats and they all open around the 88°C mark. I have not yet changed the water temperature sender mainly because the temperature of the air from the vents was following the gauge so I’m guessing that the sender is working. All so I have not seen either of the cooling fans kick in. The AC on this car is super cold but it’s not that warm outside. Has anyone got any ideas on what could be wrong?
Cheers all

 

The instrument cluster gauge is not very accurate , it is a dummy guage

The temp sensor for the gauge is the single wire on top of the thermostat housing

The 2 wire is the engine ECU that brings the engine into closed loop efficient mode , 88 C

The copper crush washer on the single wire sensor can be sanded to conduct better

The instrument cluster can and has been moded to be more accurate and resposive

 

The AJ6/16 thermostats fail OPEN!!!!!!!!!!!!(the V8 thermostats fail CLOSED/OVERHEAT)

Replace the thermostat and DO NOT USE the O ring that sometimes comes with it. (flat gasket for the AJ16)

 

To test the radiator fans with the engine not running or warmed up , key in run position

Remove the 3 wire connector on the rear aft car's left of the radiator

With a paper clip jumper one of the white wires to the black and you will get low fans mode

Remove the clip and install between the other white wire to the same black and you will get high fans mode

This is a low current section of the circuit so no arcing hazard

Caution on removing the fan motor connector if done so as the plastic connector lock on tab can break if levered too far , so just enough

If you have the factory TSB done you will have the 2 wire freon pressure switch connector removed and the 2 wires jumperd

14-04 (jagrepair.com)

 

Hi all thanks for the replies. I have tried three different thermostats all rated at 88°C and this has made no difference at all. I have noticed that the fuse number 11 in the left hand side engine bay has popped. It is a 30Amp one. I replaced it but with minutes of the engine running it popped again. All I know is that this fuse runs the fan. Fuse 17 which is also a 30Amp fuse also runs the fans and this one is ok. I will do the paper clip check later on today but the fans have never come on but I’ve only had the car for two weeks now. The fact that the fan speed fuse position 11 keeps popping does this mean that the fan or fans are dead?

 

New update. Disconnected the radiator switch and tested the fans by bridging the wires. I only got the fan to run at one speed if I tried the other white wire the fans will not run. Now with the radiator switch disconnected if I put the key in and turn it both fans run and the fuse does not pop BUT if I reconnect the switch the fuse will pop and both fans stop. So is it the radiator switch or the relay that has failed?

 

Got a good one

The jist of the TSB is they don't want both fans at the same time to from stopped to starting with the starting current being the highest as the electric motors start up

To go from low to high is OK but not zero to high

Your Fan Control Relay module should be white in color and not black like later V - 8 1998 and on , located under the car fwd of the left fwd tire

It should not be mounted upside down as water can get in

The connector / wires should be down

The fans are controlled in 2 ways , the coolant temp switch on the radiator and the Freon pressure switches

The problem accurse when the 4 wire freon pressure switch is closed


Do you have the jumper plug on the 2 wire freon switch saying the TSB is done ?

 

hi there
my car has had the TSB done and has the shorting wire fitted. I will have a look at the relay tomorrow to see what colour it is.

 

I’m guessing it will be ok to drive the car with the radiator switch disconnected?
the fans will be running all the time but only in the slow speed setting which is better that not having any fans running at all like it was

 

No

You have no engine overheat protection as it goes high but with the fans in low mode you have some

The engine cooling capacity is overbuild and the coolant temp getting that high requires the engine run really hard

The freon pressure switches ensure the fans give adequate air flow across the A / C condenser independent of the engine coolant needs

You can have the cabin heat on full heat temperature and cabin fans on high to make up for radiator heat dissipation shortage

there is no overheat warning light . the instrument cluster gauge is a dummy gauge in respect to its accuracy but is a rough indication

 

No as in do not run the car with the radiator switch disconnected?

the problem is if I connect the radiator switch back up it blows the fuse and I will have no fun’s at all. If I leave the switch disconnected the fans will run continuously ( as long as the key is in the ignition) so I will have some cooling

 

You can run the engine with the fans running and switch disconnected with hard engine running precautions , and cabin heat on full hot temperature setting , cabin fans on high , windows down to keep the cabin heater matrix drawing the max out of the coolant fluid

 

Thank you for your help 👍🏻

 

You can put a meter on the 3 wire coolant temp switch and see what it is doing

You can remove it and test with boiling water

closing points are 86 and 100 C , you only need to cheek 100 C FOR HIGH FANS MODE

you can read it from the module connector to be easier as the small size White / Blue color wire ( pin position 7 ) to car frame ground

The low temp closing is irrelevant with the TSB done

The high temp should be open with cool fluid , Switch can remain installed

The color of the large Fan Control Relay module may be correct but damage done from water intrusion , I cut mine open to see contacts corroded / fused closed , mine was mounted with connector up as a broken mount lug / ear so hanging from wire loom

Item # 5 if you click the + icon

Genuine Relays For Jaguar Xj 1995 - 1997 (from 720125 To 812255) (x300) Classic | Jaguar Land Rover Classic Parts

 

hi there I’ve got a little confused. I have unplugged the radiator temperature switch and now when the AC is on both fans will briefly kick in for a few seconds and then turn off again in a stable pattern this never happened when the radiator temperature switch was plugged in. So I now the fans work but I can not get the fans to work if I put a paper clip linking the black wire and either of the white wires, any idea what this means? Also if I plug the radiator temperature switch back on it just pops fuse 11.

 

give me a bit as multitasking

 

As the A/C compressor first starts the compressed freon ( liquid ) must pass through the thermoexpansion valve after the 2 separate pressure switches

This is a restriction that keeps the pressure high in the freon lines until the system ( lines ) come to equilibrium / stable

Keep A / C off

" So I now the fans work but I can not get the fans to work if I put a paper clip linking the black wire "

The Module is changing condition as something rattling around loose

Clean Black wire ground stud

 

I may have missed something, but was the problem not that the car is running too cool, even without the fans running?
Presumably with the fans running, it is now running even cooler?
As to the question of whether it can be driven, the answer is surely yes, unless it is low on coolant. (You have checked the coolant level…?) . Running with the engine too cool is inefficient and in extremis would increase wear, it shouldn’t be a short term concern.
Coupled with the cabin temperature fluctuations, your initial diagnosis of the thermostat is straight out of the textbook. As has earlier been suggested, you haven’t fitted the O ring by any chance when you replaced it?

 

hi there. Yes I agree my problem is getting messy. I will start from the beginning and clear things up a little.

I noticed that the water temperature gauge was fluctuating and at first it was linked to road speed, the faster I went the colder it got and so on. I decided to replace the thermostat ( three different ones have now been fitted) but this has made now difference. Over the next few days the temperature gauge was reading colder and colder and now it will read stone cold most of the time but if I come to a stop it will start reading some temperature. Every now and again the gauge needle will hit the half way point but it will not stay there it will always fall back to stone cold.

next issue was that the hot air coming out of the vents would follow the temperature gauge needle. So that also points to the thermostat not working correctly but even if the thermostat failed in the open position surly the temperature gauge would not read stone cold?

the next issue that I found out yesterday was the fuse 11 in the front left engine bay which is a 30 Amp fuse for the fan speed had popped fuse 17 which controls the other fan speed was ok. I replaced the popped fuse and started the engine. As the engine warmed up you saw both the fans kick in for less than a second and the number 7 fuse popped again.
I unplugged the radiator temperature switch that controls the relay and bridge the black wire with one of the white wires and both fans ran but I couldn’t get the fans to run when i bridge the other white wire. With the radiator switch plug disconnected I turn on the ignition and both fans were running but that has now stopped happening but if I put a high demand on the AC system both fans will cycle on and off. I tried connecting the radiator plug again this morning but it just popped the fuse again.

This morning I had a stone cold reading from the temperature gauge BUT I did have nice hot air coming out of the air vents in the cabin.

the radiator is nice and hot, the upper radiator hose takes time to get heat and the lower radiator hose is always the last hose to warm up.

I hope this has made my issues a little clearer. Even I was struggling to understand what I had written

Also I have no O ring fitted on my thermostat, I have just used the two hole gasket to seal the thermostat cover to the housing, is this correct?

 

I would agree that your symptoms are classic Thermostat, but if you've replaced it 3 times then it might be time to think laterally - not sure what though.

Here's a couple of tests you could do to confirm that the temp gauge is actually telling the truth.

1. Use Live Data on an OBD tool to look at the engine temperature. This is the ECU feed of temperature and comes from a different sensor to the the gauge. Does it correlate with the gauge?

2. AFAIK both temp sensors work on a variable resistance to ground. If the main engine ground strap is loose/corroded then that would give a high resistance which would impact on both readings. Use some jump leads to bridge between the engine block and a good ground on the body as a test.


The fact that you get cool air out of the vents when the temp gauge reads low could be that the system is clever enough to shut off the heater solenoid valve if it thinks the coolant is cold? I don't know this, just trying to think of a reason that isn't the thermostat.