Brief history, car parked on driveway with gradient, river beside burst banks xk8 in 4ft of water for about 4 hrs.
Hasn't run since 2008. New fuse/relay/boot module,new fuel pump (thanks to Gus for the step by step legend mate).
Full service and coolant, new seats and full electric motors and modules fitted.
New head unit and A/C controls
New central locking plus loads of niggly things. I was able to tackle all the jobs because of this site and in particular this thread.
https://www.jaguarforums.com/forum/x...ts-data-29800/
I would likre to thank everyone who contributed to it too many to mention here so big thanks.

 

So car now runs, me thinking i'm a legend calls customer to hand back car while engine running, guess what? hose explodes of the theromstat housing showering everywhere in coolant, I **** 2 different types of bricks thought i'd wrecked this guys car.

From reading around the forum i've seen its happened to quite alot of people so that eased my pain.

Anyway im digagnosing the cause, hose back on filled with water and engine goes (praise jesus).

Here's what i've done so far.

 

I've tested the thermostat by boiling it in water and it opens and closes no problem. The water is circulating ok as both hoses from and too the t-stat get hot after running.

Thats when I notced the fans wern't coming on car had been running for a good 15 mins, i tried the A/C still no fans.
checked fuses and all are good.
Fuse #12 (10A) Engine Management Fuse Box..... 12v to low speed relay
Fuse #12 (30A) Engine Compartment Fuse Box..... 12v to High speed fan
Fuse #14 (30A) Engine Compartment Fuse box..... 12v to Relays.

I then went for the cooling fan relay, the green lines are to the ecu and by back probing i was able to see the voltages to and from the relay,

[IMG]https://www.jaguarforums.com/forum/

 

I could see with my volt meter that the signal from the ecu was working as the volts dropped as the temp went up. On the relay it's self you have 8 pins with 7 populated,I noticed that the orange/yellow which connects to the left fan never got any voltage when the temp went up, the signal from the ecu should switch or pull up this wire to 12v to power on that fan, it should also pull down the green/orange wire to ground to power the other fan.

 

Relay,

 

To confirm the relay was bad I bench tested it and confirmed no continuty, I opened it up also just to double double check. Really bad water damage,old and new.

 

New relay fitted but still no fans, i used my power prode to manually turn the fans on, With a volt meter you can test the voltage at each fan, the left fan will have 2 grounds, and the right fan 2 12volts.With the relay unplugged you can give the orange/yellow wire 12 volt(powers left fan) and the orange/green wire ground (powers right fan).
So both fans worked but not being turned on by the car, even with the new relay and the A/C on still no fans. I then did the 100ohm resistance test on the ECT sensor, happy days fans a blaze.

 

Does this mean a faulty temp sensor if so would it stop the fans coming on when the A/C has been swithed on, also i read this post by Gus which is pointing me in that direction as the temp gauge on the dash works fine.

QUOTE.
I would check the fuse first then the a/c relay and then the operation pressure on the a/c system. You will need a set of gauges to do this. You might say why the pressure? You’re a/c system has a pressure switch that is mounted below and between the fans. If the pressure in not correct in the system it will not let the a/c compressor engage. This switch also controls the cooling fans. If I recall the sequence, start the car with the a/c off, turn the a/c on and the compressor should engage and the cooling fans should turn on. I had the same problem and it was the pressure switch. I hope this helps!



Is there a way to test and condem both the tep sensor and the A/C pressure switch.

 

Just back from Holiday and going from the lack of replies I haven't read/researched enough LoL.

The answer to the ECT sensor test was staring me in the face looking at it now i feel stupid i didn't spot it before. I took the sensor out of it's housing and plugged the hole. I then plugged the sensor back into its harness and with a heat gun heated the eliment for about 2 mins, this triggered the fans which proved the sensor as well as the full system is working fine.

I'm starting to think it takes to long at idle to get up to temp to trigger the fans I might have to bite the bullet and drive the car and see.

Also I have done the A/C code test preceedure and i'm getting code 12,
12 Ambient temperature sensor malfunction Harness / connector fault Sensor open / short circuit
After rectification, disconnect the vehicle battery for 10 seconds to reset the system.

And 23,
23 Refrigerant pressure switch malfunction Harness / connector fault Switch open / short circuit
Refer to PDU23 Refrigerant pressure low refrigerant charge *Leak from damaged pipe or joint
Rectify as required and recharge system.

If the refridgerant is low and causing the refridgerant pressure switch to shut of would this keep the fans off all together?.

 

Seems as if your thread got lost there for a while...but you have done an admirable job answering your own questions!

The normal temperature for the fans to come on is about 215 F. If you have an OBDII reader with real time capabilities you can monitor this.

Yes, the A/C 4-way pressure switch does affect fan operation.

 

Just to throw a spanner in the works a mechanic friend has suggested an air lock(I followed the coolant change to the letter by the how to on here), clogged rad or failed fuel pump. I'm getting my scanner back tomorrow I'll be able to see the running temp and confirm if the fans should be running. Any pointers on water pump diagnosis or checking for a clogged rad(I've noticed the rad doesn't get hot at all when engine running) so now I'm leaning that way.

**EDIT** not fuel pump water pump.

 

After sitting around that long, an internally corroded and clogged radiator seems pretty plausible.

 

Ok, i think the problem was lack of confidence. I took the ect sensor out again and put the heat on it while watching the temp on the scanner. At a little over 100*c the fans went, I opened the coolant resevior while the engine ran and I could see movement not just turbulence but moving with a purpose and in the direction of flow given in the cooling system diagram , this gave me some confidence the water pump was ok as for the clogged rad i still wasn't sure. Anyway I bit the bullet and took it for a drive while watching the scanner after it got up to 105*c i stopped and jumped out happy days the fans were on and i could now see the temp drop on the scan tool. After that i parked up an kept the engine running turning both hot and cold air on full blast the cold was cold the hot was hot .

With the air con on the engine temp rose to over 100 then the twin fans came on and it dropped down to about 90, i did this a few times and each time it worked flawlessly. By this stage i was confident i wasn't gonna overheat the car so i left it running for ages keeping an eye on the temp, finally i got a hot at the top and cold at the bottom rad which was a joyful thing.