Cooling fan module (X-Type)
 

If this thread must be in the X-Type section, can someone from the moderators move it there? Thanks.

So, after recently getting a 2003 X-Type 2.5 I discovered my cooling fan control module was not functioning. As you know the usual options are to get a second-hand one, or buy the whole fan assembly with the motors, propellers, control module, etc.

I decided, however, to check what's inside this module, so here it is:
https://lh4.googleusercontent.com/-z...o/IMG_0830.JPG

Apparently it's a circuit board with some kind of processor, for handling CAN communication I guess, and two circuits for operating each of the fans.

I could see that one of the elements at the top, which turned out to be a transistor, and one resistor were burnt. So, I decided to give it a try replacing them. The transistor is not that common (BUK9506), so finding it took a few days.

In the end, both it and the resistor were replaced and I tested the module on the car (without putting it back in the closing). It worked!!! But while fooling around the bonnet one of the transistors burst into sparks again...

Long story short, it turned out that the lower fan has problems and its drawing very high current, which overloads the circuit. This was discovered by connecting it directly to the battery with two wires. It was spinning, but the wires were getting burning hot, which was not the case with the other fan.

Anyway, the transistor was replaced again, the board was put back into its enclosure, and I decided to go "bonkers" and attached a small cooling fan for the module only:
https://lh3.googleusercontent.com/-c...o/IMG0002A.jpg
https://lh4.googleusercontent.com/-U...o/IMG_0838.JPG
https://lh5.googleusercontent.com/-z...o/IMG_0837.JPG

I got power for it from the left-hand lights. Not sure of the English word for it, but it's the smallest bulb there. The 5W one. No idea it'll help but it won't hurt for sure, as it's mandatory drive with lights on all the time in Bulgaria.

I also took the fan motor apart and one of the brushes was detached. Fixed that, and changed the bearing at the front (the back has no bearing, so just lubed it there). Put everything back together and it worked like a charm... For a while that is. It turned out the lower fan was still not running OK and eventually I guess it burnt the circuit again.

Most probably it's also related to the fact that the fan blade is cracked and it's grinding against the casing. I haven't bothered to disassemble everything again to check and test. Just unplugged the troublesome fan and left only the upper one, which works OK. (I won't be needing them anytime soon anyway.)

So, the moral of all this story I guess is that if you have a failed module, you:

1. Can repair it;

2. Check the fans as if either of them is problematic, most probably it'll fail a new control module too; and

3. If only one of the fan circuits is faulty, the other one can still function, but you have to unplug the bad one.

Thanks for checking this long read, and I hope it's useful for someone.

Cheers,
Krasi

How do you know your cooling fan control module was not working?

Well, if it starts to overheat in stop-n-go traffic :icon_cool:

Also when you switch A/C on, cooling fans should begin to work regardless of ambient and engine temperature.

Krasi, you are correct in a quasi sort of way. The fans will kick on more often, but only if you put the car into MAX A/C will the fans run all the time. You can prove this by having your car parked and turning on the normal A/C. You will see the fans kick on and off. But, you put the system in to MAX A/C, the fans will run all the time at max speed.

Well, having cooling fans switch on and off pretty much proves the controlling module works.

The "proper" way to check though, according to a workshop manual I have, is to unplug the coolant temp sensor (located above the oil filling cap on the left hand side of the engine; under the plastic cover I think), and stick a 100 ohm resistor in the plug to simulate very high coolant temperature.

What are the numbers on all the transistors? I have this same problem, I need to order a new unit. But, if I can replace the transistors I'll do it that way.
Now, 3 of the transistors are melted, one isn't. All the capacitors are good. And how did you reattach the heatsinc?

The transistors on the left and right are identical - BUK9506-55A. The two in the middle are also identical but I don't remember their names, so not sure if they are transistors or thyristors, or something else. Mine were OK.

I drilled the rivets of the heatsink and replaced them with 3mm bolts. Yep, I made threads in the case, which wasn't difficult as it's some kind of aluminium, i.e. quite soft. To top it off, I put quite a bit of thermal paste all around the heatsink and the transistors.

Question
 

So do these transistors blow because of heat, or do they blow because of a voltage spike?

Not sure, but probably both.

I'm not a specialist, but there is something strange with the design of the whole circuit. I mean, the maximal drain current of the BUK9506 transistor is 75A, while the protecting fuse is 80A:

http://www.nxp.com/documents/data_sheet/BUK9506-55B.pdf

I think with this setup and getting some 80+ degrees of the transistor (as it's next to the radiator and will be used only when the engine temp is probably above 90) it's bound for the transistor to burn first rather than the fuse, because of "blocked" power dissipation.

Or, this could all be totally wrong, as I've studied these things almost 20 years ago....

The Fans kick on low when the engine coolant is at 203 F, on high when it hits 221 F, (or when you turn on the A/C.)

So, it seems that it's a design flaw? What would happen if you put a different Transistor in there? Like one that could handle 85A? I have to admit that I know nothing about transistors...

Not sure if it's a design flaw, or it was done intentionally for some reason. But they changed this module in 2004 or 2005, so something must have been wrong with this design.

I'm not sure there are transistors with higher drain current in such casing. AFAIK, they need to have bigger bodies in order to dissipate the heat. Maybe they used such in the new version of the module :)

Quick update to the above just for completeness: there is a Jaguar technical Service bulletin on this subject which advises dealers to swap modules out even before the car is collected by the customer. Reason given is:




The cooling fan module on X-TYPE vehicles may fail under certain circumstances.
There are various root causes but the design and quality of the printed circuit board
within the cooling fan module are the most significant. The NAND gate used in the
circuit is defective causing multiple failure modes, this can result in high engine
temperature and overheating due to the cooling fans not operating.
A change has been implemented in production from VIN C91720. On these vehicles a
‘Philips’ printed circuit board has been used that has a modified voltage spike protection
strategy.

Dear,
can you share the pictures, i know this post is old but i am having this problem with my fan control module, and i would like to open it.

thank you

Older first year models module, but same basics =


There is a tool to test ANY CAR and ANY MODULE (including fan modules from low through the variable stages to full on) as well as program modules and ECU, BUT.....BUT....Holy moly, the cost!!!

thank you, i saw this one a while back, it is for the old type, starting 2004 they changed it , it no longer has cables coming out, only 3 sockets,

The other option if you are ABSOLUTELY sure the module is toast, is contact member Dr. Dome who parts out X's for a replacement.