While on a run today, with the outside temperature as registered by the car at 45 deg C, the whole air system suddenly failed. No fan, no air whatsoever at any speed from any outlet and most options on the climate touch screen left hand column greyed out. The temperature buttons do adjust the values shown on the screen however but, of course, nothing happens.. No warning lights on the dash either. The two local Jag dealers are not interested in a 2007 car so don't know what to do now. Can anyone give me some pointers to get started with a diagnosis?
BTW it was not a pleasant drive home!

 

Sounds like something went wonky in the module. Reading the climate control module for any codes would be my start

 

Thanks for that. Would I need an SDD scanner or would any old one do for this? Sorry but this is the first time I have had to scan any car.

 

There is a resistor on the heater box that goes out a LOT on the 4.2 cars due to moisture. I don't personally know where it is, but there are several threads on this in this forum. Try using the search for "fan resistor" or something like that.

 

Could be the temp control module - I would check the fuse in the central junction box (located in the driver side foot well)

 

Of course it did… its hot outside.
Then follow the pinpoint tests in the workshop manual.

 

Remove blower motor (beneath glove-box). Then trace wire to what is the blower control module. Remove module. Generic replacements are available at most any automotive parts store, under $50. Just make sure the pinout is the same as yours. If you're handy electronically, module is easily disassembled and you can replace the power transistor (FET) and / or the thermal fuse. (Old technician joke: transistor blows to protect fuse).
Make sure fan is moving freely; mine seized up causing module failure.

 

Agreed it’s probably the blower motor resistor module. As mentioned it’s right next to the blower motor with 2 screws holding it in situ
The internal thermal resistor is rated around 115 degrees.
The module is the same a Range Rover one and you can get them Ebay from around £20
This fuse often blows when the blower motor has gotten stiff or rusty due to the duckbill water ingress. Is your carpet damp

You can take the Resistor module apart and change the fuse and these cost around £2 each
If you attempt this don’t do as I did and try and solder the new one on as this immediately blows the new fuse.
You need some small crimps to connect to the tails

 

Well I have checked the fan motor out of its housing and it rotates without catching anywhere although there is a little stiffness which I put down to the characteristic of a permanent magnet motor. On applying 12V to the motor terminals it works fine.
I also checked the voltage at the main connector on the heater housing which read 13.8V (CTEK connected.)
With the ignition on and the fan control turned right up the voltage at the motor connector (disconnected from the motor) was !0.6V and remained the same even when the fan control was turned to a minimum. However this may be meaningless without the motor connected as I don't understand how the resistor circuit works.
All fuses OK.
Now what to try? As I mentioned in my first post part of the climate section of the touchscreen is greyed out. Is this relevant?
I hope for some ideas.
In the meantime tomorrow I will try to buy or order a resistor unit but it may take a while to arrive.

Thanks to all for your help so far.

 

Sounds like the resistor to me.

 

I wouldn't be in any rush to buy a resistor module - do some multi-meter checks on in it first - post a pic of the greyed out screen.

Check this resistor thread out:

https://www.jaguarforums.com/forum/x...e-%245-184627/

 

I had already found that thread thanks to a previous poster and it has proved useful. I don't hink I,m up to repairing the module but could perhaps run a continuity test. However I'm having trouble at the moment getting tone of the retaining screws out as access is so difficult, not to mention the heat this afternoon.

Picture of screen is attached, if I can upload it. Everything associated with this Jag seems to be first time! I don't know how to make the picture smaller. Sorry.



Climate screen with "greyed out" sections

 

This is what's inside the blower control module, for those curious.

The FET is the squarish component. The thermal fuse (not in photo) sits nearby the FET.

 

So it's not a resistor module as it has been called.

 

If you rotate the fan knob is there any change in the display graph. Can you select any of the vent positions and change the color? - What about other functions on the screen such as valet etc and do they work?

 

Thanks for that. I will be back to you on these items. I have too much disconnected at the moment to risk starting anything just now. I have just blown the courtesy lights somehow while attempting to get that second screw out of the control module. I'll have to look into that too. There was quite a "pop" when that happened so I hope I haven't damaged much. Anyway the 'resistor@ module is out now. I haven't decided whether to investigate or just buy a replacement.

 

When you get it all back together maybe try a battery disconnect/hard reset if you haven't tried that already.

 

[QUOTE=McJag222;2770053]So it's not a resistor module as it has been called.[/QUOTE

Its commonly referred to as a "resistor module", but is a little more sophisticated than that.
A small signal voltage to the FET allows the FET to control a larger current / voltage output. It's kinda like a solid-state variable resistor, along the lines of a dimmer you might find in your house.

 

It's still not a resistor - in the same way a transistor (transfer-resistor) ain't a resistor. A light dimmer is not a variable resistor it's a dual diode that is triggered through a gate terminal at varying points of the AC cycle, it's either on or off.

 

Having opened the control module I found the thermal "fuse" open circuit. I spent several hours trying to track down a new module for either Jaguar, Land Rover or even Subaru, without success locally or even in Spain except at the JLR dealer. So it has to come from the UK or further afield in Europe with consequent delay. I will revive this when I have fitted the control module.

As to the resistor discussion I suppose it is called that because that is what they used to be in the past. However the reference to dimmers and resistors is wrong too. In the days when I was involved with theatrical lighting the lamp dimmers were all big variable resistors and gave off lots of heat usually in a small room at the back of the auditorium. I can feel sweaty just thinking about them.

Thanks for the help and especially Cee Jay who mentioned the "resistor" first.