FBH The end of the SAGA ?

[FrenchMike]

Originally Posted by David Lawrence

It was a solder joint this time. It seems the chewing gum has attacked the joints on the resistors which was very confusing because when measuring the resistors on the top of their caps they read fine, but when I scraped away the varnish on the pads and measured there, they read open circuit. Ended up replacing 2 x 4.7K resistors and 1 x 10K one.


That chewing gum has a lot to answer for.

Yes,chewing gum + temperature

[stevejspm]

I would like to offer my sincerest thanks & gratitude to FRENCHMIKE for sharing his knowledge on fixing the Webasto. I have a BMW X5 & as a result of following his diagnosis & repair procedure I successfully repaired mine today.

Well done FRENCHMIKE & a big round of applause to you! Thank you so much.

[FrenchMike]

Originally Posted by stevejspm

I would like to offer my sincerest thanks & gratitude to FRENCHMIKE for sharing his knowledge on fixing the Webasto. I have a BMW X5 & as a result of following his diagnosis & repair procedure I successfully repaired mine today.

Well done FRENCHMIKE & a big round of applause to you! Thank you so much.

Very happy for you Steve and glad saving
all these condamned webasto's...

Mike

[mashby]

Originally Posted by FrenchMike

MY STORY:

I came upon this Forum 3 years ago after my in tank fuel pump broke.
I found advice here to have my pump quickly and cheaply repaired.

I too also had the strange Fuel Burning Heater (FBH) behaviour caused by the K bus.
(Which I have since disconnected.)

As a regular reader, I have noted lots of threads about FBH issues and in particular
that the PCB was reported as being non repairable.

The cold days made me inclined to study the question. I began by trying to collect information about the circuit diagram etc, (not very easy)

At first I thought the Interface IC bus was the culprit.
I ordered the genuine interface IC bus (ELMOS 10026B) from Hong-Kong,
but one month later, nothing ;they forgot to ship
Meantime, I bought the Riesler interface Bus describe by Keith Alexander .
I discovered than his Interface Bus IC was a (Melexis TH3122) similar
and more easy to get.

Next, I built up a test bench and established communication between my laptop and
the Webasto PCB.
However, there was a combustion air fan error. (running at max speed).
Tracing the PCB ‘tracks’, I discovered than the power Mosfet’driver was always
ON although the Micro bus line concerned was live .The link is in fact a SMD (surface mounted) resistor well hidden under a kind of sticky sealant (looks like meringue.)
The resistor was marked 4.75 kOhms but my multimeter showed infinite !
Strange ,I had rarely seen that before in my professional live.

Anyway, I quickly replaced it and …..everything worked …..

I opened a new thread on the forums to tell the news.

So, the only possible cause, was that the resistors were being attacked by a chemical agent from that paste (meringue).

(can you imagine how many Webastos this may have affected all over the world !!)

I would like to freely publicise this valuable information, in the true spirit of the ‘Forum’ and it’s ethos of sharing information.

Most members will be able to do the work for themselves ( or know a man that can!).
However, I can do the repair for others who don’t feel like tackling the job themselves

TOOLS NEEDED:

Low power soldering iron with thin tip correctly earthed.
Table magnifier,
Solder
SM (surface mounted) resistors 4.7 Kohm ; 47Kohm


PROCEDURE

Extract the PCB from the FBH (5 screws)

Pic 1


Remove that sticky white paste and clean the area to show the resistors.
Take a measurement of them: two 4.75 Kohm and one 47 Kohm.


Pic2



If possible, built a test bench for checking out all the parameters before fitting on car.

Pic3



Results

Pic4



Enjoy your warmer car :lol:

Mike

Mike,

I have a 2005 E53 with a erratic running combustion fan motor. It will start OK run for about 2 minutes then run erratically & shut down with INPA message Fan interruption. Have read about faulty 4.7k resistors in PCB but could it be clogged combustion chamber causing flame out? Can you repair BMW PCD's. I am capable of changing resistors but don't want to start until sure that fault is PCB?

Would appreciate your thoughts

Mark A

[FrenchMike]

Hi Mark,

You have to know that i can't test entirely the BMW one's for the cycle is
depending on the Kbus 'car.

I only can test the driving of the external components .and read the recorded
errors.

The Rover's are more easy to test ..

However,i can still have a look

Mike

[cowmanmick]

my fbh wont fire up it runs but doesnt fire is it the pcb i would like french mike to have a look at it have anyone got a contact address for him ,or can mike please contact me himself,i would be apreciated for any help

[klarzy]

Originally Posted by cowmanmick

my fbh wont fire up it runs but doesnt fire is it the pcb i would like french mike to have a look at it have anyone got a contact address for him ,or can mike please contact me himself,i would be apreciated for any help

just click on his name and send him a PM....

[mashby]

Mike,

Do you still do PCB repairs?

[wolfdoguk]

Hi, and happy new year to everyone. My first post after being a member for ages, apart from P.Ming big russ and having him remap 2 ecu's. I don't really want to impose on the good people here, but I feel I need some answers from the boffins here! I have ploughed through endless threads and posts, but just got mesmerised, so I hope it's ok to post here!

I have a unhealthy obsession with fbh's, especially after reading the endless information on this site about them, and past experience with cab heaters in my trucks!
I have one already fitted to my saloon, but I bought one complete with pump, and retro- fitted it to my 52 plate tourer.
As soon as I put fuse 8 in, the fan motor burst into life and ran a few seconds. I couldn't get it to run at all after that, it was dead, tried resetting it by removing the fuse, but still nothing on earthing pin 6. I replaced the fuse a day or so later and it fired up and ran! I was a happy chappy! However, after a week it just started running the fan and the water pump, but it just wouldn't fire. I tried resetting again, but nothing.
I have a perfectly good one, which I know works on my 75 saloon, swapped them round, it did the same thing when connecting the battery to the saloon, only this time it burst into life, only to cut out and just run the fan, blowing cold air out of the exhaust and circulating water. Fired up the known good one on the tourer (originally off the saloon) and it worked perfectly!!..... For a week.... Now, Monday, that one has started the same game!! Although, this one doesn't start running on connecting the fuse, symptoms are the same, i.e. running the fan (a little faster than usual) and water pump, but not firing!I also bought 2 gsm's off ebay after reading all about them on here, but they aren't without their faults either!! one doesn't quite work as it should, although, i have no instructions apart from what's on the listing and what i can squeeze out of the guy by asking! and the other didn't work at all!!!!I also fitted the maplin relay on the heater
too, as done by another excellent life-saving-member, it was lovely while i had it all working "to a fashion"! Now, someone mentioned that they aren't very good as anchors or doorstops, but I'm liking the idea of donning my steel toe cap boots and launching them like rugby balls, or, a splash of petrol and a match to activate them....I hope the other genius aka FrenchMike reads this, because, surely it would be an unlikely coincidence that both pcb's fail, and in the same way in such a short time? unless it's something that is blowing the resistors, but there's only the 5c temp wire, dosing pump and pin 6 earth activator fitted, the k-bus is disconnected.On another note, i removed the first pcb, cleaned off the gum around the capacitors and found the furthest right one was black on where it had sat on the resistors I also took out the pcb for the other fbh, but surprisingly, this one is almost charred under the blob of gum,on the right of the pcb. Now, another God "HarryM1BYT" shows a picture of a different resistor marked as one of the" failers" to what FrenchMike shows in his picture, unless I'm looking at it wrong, but does anyone know what type the other resistors are and what size they are in that area on the board, under the blob? and what particular size they are, ohm, wattage and physical size etc, or doesn't it matter? if a reading can't be found with a multimeter (i just bought a new one, and both my old one and new one don't show any readings, as if they are open circuit, so how do we know what to replace them with?! i'm not a big electrical wizzard, in fact i've never tackled anything as small and fiddly as these resistors) I've just ordered a table magnifier in the hope of doing these myself....
Even "if", by some miracle I get them fixed, I'll still be worried about putting it back on the car in case it blows again!
I've attached a couple of pictures of the bought pcb (first one to snuff it) which seems to show one of the offending resistors looking suspect and the pcb from the known good one (well, was a good one...) Showing the charred area around the right hand capacitor where the gum was.
Any pointers and/ or ideas would be gratefully received.

Thank you very much!
Paul

[wolfdoguk]

Originally Posted by FrenchMike

Hi Paul,

it seems you get several issues ; you have to know for safety reasons a error
is produced in case of:

Battery voltage lower than 10.5 volts
-Glow plug open or short circuit
-Circulation pump open or short circuit
-Combustion fan open or short circuit
-Fuel pump open or short circuit
-PCB defective

Check separately each component.

Attachment 43798


Never remove power (fuse or 2 pin plug) before removing the 6 pin connector.

For test at any temp , connect pin 3 to earth (NOT pin 6)

Good luck

Mike

Thanks for that Mike, much appreciated.
Yes, silly me, I meant to say pin 3 of the 6pin plug, I use this to activate it via the gsm.
I wouldn't think there would be anything wrong with the fan, pump and glowpin, as it would be a coincidence to have the same fault on two different burners, but of course it can't be ruled out, I would suspect the fuel pump wiring, but not too sure how to check it. The batteries on both cars are very healthy, showing over 12.5 volts.
I'll try your test when I get chance, thank you for that.
What would you advise on resistors there, as they look pretty fried on the second pcb?
Thank you very much.

Paul