XSeries-forum

Well I am a newbie to the X5, but not to BMs. A search showed a very long thread, so please forgive me if I ask for a pointer without ploughing through that whole thread...

I rather assumed that the (Diesel) heater was working at the time of private purchase (1 week ago), as it seemed to fire up as soon as any door, including the rear hatch, is opened. It shuts down maybe a minute later. If a door has been left open, and it has  shut down, closing a door causes it to fire up again. By fire up, I mean the air fan kicks in, and cold air exits the heater exhaust. Fuse 59 20amp is present and good. This frequency of starting does not seem right, and starting the engine does not alter this behaviour

By coincidence, I have largely completed the install of a petrol version into my E38, so I have dismantled and serviced the earlier Thermotop S version, so I am reasonably familiar with the unit, fuel pump etc. and the whole E38 set up, but not the X5. My X5 does not have a Telematic remote, and has the basic MID, no widescreen.

Since 12v must be present at the unit for the air fan to function, I am leaning towards a check order of the heater water pump, burner unit, glow plug, fuel pump, pcb. I also have INPA working.

Am I on the right track with this?
Is there a resistance value available for the glow plug?
When the fault is identified, is it sufficient to clear any codes with INPA, or is there another sequence, such as battery disconnect for x time, remove / replace fuse(s)?

Grateful for your help....

Welcome

Certainly doesn't sound right.  It should only run if the outside temp falls below 5C or if you have auxiliary heating installed when you require it.  At this time of year nothing should happen at all.

Putting 12V on pin 1 will cause it to start and run through the cycle.

Do you know if the system has been played with and someone has tried to incorrectly enable aux heating?

Well worth having a look to see if any faults have been stored and/or the wiring has been played with and/or there is a control module for aux heating plugged in to the boot mounted modules area by the battery.

Richard

Thank you Richard, that was quick.

This car does not seem to have been molested at all. I presume you mean pin1 at the heater?
Are the modules you refer to in a box behind the battery? - If you are think of the Telematics module, I think that is similar to the E38, and I can recognise that..

Pin 1 on the Webasto, yes.

Down by the battery yes.  It could be called a 'telematics' module.  It was a Webasto T70/T80 or T90 remote control module if memory serves.  Expensive and hard to find nowadays.

Richard

As standard the webasto would only operate when you start the engine (or turn ignition to poss2) and outside temp is less than 5deg and coolant temp less than 15deg and battery voltage ok and there is sufficient fuel in the tank...

Aux heater function is not an European spec (only US) as standard.
It can be enabled so that you can set a timer (or two) on the MID which will cut the heater in, and turn the interior fan on to defrost and warm the car.
Will need appropriate interface and program to enable it.

Thank you both. Since the o/s temp criterion is not met, there must be a problem-is this picked by the cars own o/s sensor-I've not checked that?  I put 12v onto the heater water pump last night and that's running fine. After the commute home, the aux heater was certainly hot, so coolant appears to be flowing through it. Tonight I will check the glow plug resistance which I believe should be 0.3-0.6 ohms? Also see if 12v will get the fuel pump to tick. Then we'll see..

By the way most of my Thermotop S parts came via ebay.de-all sorts there.

You might see an error in the car fault logs.  Otherwise a trawl through the thread, or a search on those who have fixed/repaired their Webastos may give you clues.

Richard

I'm 99% sure I know what the issue is as I had exactly the same symptoms with mine.....

The fault almost certainly lies with the PCB in the Webbasto itself, that's not to say another component may be defective but I would certainly look at the PCB first. I repaired mine myself by fault finding the PCB & replacing 3 defective components. I've also repaired 3 other forum members PCB's also. I'd be more than happy to take a look if you so wish 

[quote="Stevejspm"]
I'd be more than happy to take a look if you so wish 
[/quote]

That's what this forums all about! 

Couldn't agree more Sanj, if I need some help or advice this is the first place I come to....doesn't hurt to give a little back 

[quote="Stevejspm"]
I'm 99% sure I know what the issue is as I had exactly the same symptoms with mine.....

The fault almost certainly lies with the PCB in the Webbasto itself, that's not to say another component may be defective but I would certainly look at the PCB first. I repaired mine myself by fault finding the PCB & replacing 3 defective components. I've also repaired 3 other forum members PCB's also. I'd be more than happy to take a look if you so wish 
[/quote]

Thank you for this kind offer! I may take you up on that  This is what I have achieved so far:
Air fan runs as a door opened - so OK
Tested secondary water pump by direct connection - OK
Tested glowplug resistance = 0.3 - OK
Removed the burner and cleaned - quite a lot of carbon removed.
Hooked up INPA which shows a short to earth -255 times! - cleared these in case they were old codes. Also allowed INPA to test the dosage pump - OK.

I will now remove the control unit - does the problem lie with capacitors - I seem to remember a reference to this elsewhere?

The air fan shouldn't run when you open a door, this is a sure sign of the Webasto PCB at fault. All the ones I've repaired have at minimum 2 defective resistors. Others (such as mine) have had 3 failed resistors & 1 failed capacitor. It's a bad design flaw by Webasto, they used a resin to secure the 2 large electrolytic capacitors which over time causes the components close to the resin to break down & fail.
Let me know if you want me to take a look

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