webasto whirring still!!

[goldie75]

I posted a few days ago about intermittant whirring from under the bonnet and its def from the webasto box.I've been advised to disconnect the kbus wire to it[cheers greeners] but I assume this will mean the heater no longer works.What with the winter coming[-15 in ayrshire last year!] I really need it working so just wonder what my options are.What will actually happen if I leave things as they are and what will a repair/new box cost? Thanks for all the help as per usual and apologies for lack of knowledge! Del

[Matt1960]

You need to try disconnecting the kbus lead (pin2) from the webasto 6 pin connector, as this just might be the problem. You just have to snip it somewhere along the cable. (You can always use a bullet connector to connect it back up if necessary. But its function is only as fault diagnosis on a T4 (I believe). The webasto will work perfectly well without it.
Matt

[Matt1960]

The other thing to initially test is the wire to pin1. It is just possible that the temperature sender has gone closed circuit and then the webasto will work anytime the car is running until the coolant temp gets to 72c. If then you had a main thermostat that was not functioning correctly (highly likeley) then the webasto would keep working.
So after snipping the kbus wire, and ruling this out, you need to stick a pin in the pin1(or cable coming from it) and put a voltage test meter or 12v bulb across to earth whilst the temp outside is greater than 5c, and turn the ignition on. If you get voltage, this may be the problem.
Matt

[al_dente]

Is this advice correct on all webastos? I know on the earlier cars (like mine) the pinouts are different.

Al

[Matt1960]

The main difference on the pins on the two types is that on some earlier ones, they will work with 12v on either pin1 or pin3.
The later ones will fire up with 12v on pin1 or an earth to pin3.
So either will work with 12v on pin1.
Matt

[goldie75]

Thanks Matt.Just been reading thru loads of old threads.Is it as simple as removing fuse 8 to see if that stops the whirring or do I really need to cut the wire??

[Matt1960]

Removing fuse 8 will stop the webasto as its the main power supply to it.
But I would advise at least trying to sort out the problem. At this stage we dont know whether the problem is an easy fix or expensive and difficult one.
So, if it were me, I would snip the kbus wire first, just to see.

By the way, you should not be worrying if the webasto continues to run for a few minutes after the engine is turned off. Maybe up to 5 mins.
This is quite normal and essential to cool the unit down after it has been on. It is just the fan expelling any unburnt diesel (you may see some smoke) and then cooling the unit down.
If you pulled the fuse soon after leaving the car it could overheat the webasto.

Matt

[goldie75]

Thanks again Matt..will have a look at it tomorrow..Del

[James.uk]

Try contacting "FrenchMike" he is our resident expert on the FBH... :}
...

[goldie75]

Hello chaps.Well i've cut the red and white cable and lo and behold it seems to have stopped the random whirring.The heater/aircon seems to be working ok aswell so thanks for all your help-this site is an amazing wealth of knowledge.. thanks to everyone involved...much appreciated Del

[James.uk]

I just pulled the plugs on mine till I get the PCB sorted. FrenchMike has it as we "speak". :D
...

[Matt1960]

Del,
Thats good news.
But, what you might find now is that your temp guage might not get up to the half way mark, as the webasto may possibly have been compensating for a thermostat failure.
The other thing is to find out whether the webasto is going to work when the ouside temperature gets to 5c or below. As the webasto is an absolute necessity to heat the coolant up quickly when its very cold.
Fingers crossed for you.
Matt

[Greeners]

The KBus is a weak point on the FBH and is only used if you want to run the diagnostics using the webasto software. The T4 doesn't like it.

There is a sensor under the radiator that closes at 5 degrees or colder, and will fire the engine up once running. (the 12v comes straight from the alternator)

You can add a switch or remote to fire it up when stopped but you do run the risk of a flat battery if you let it run too long.

HTH

[James.uk]

Hiya Matt. :} Whilst the FBH is a very welcome addition to our cars, it isn't essential, I got through last winter with no problems. My car got nice and warm within 3-4 miles and my FBH was NOT working. .. (I had unplugged it).. :D :D
...

[Matt1960]

Hiya Matt. :} Whilst the FBH is a very welcome addition to our cars, it isn't essential, I got through last winter with no problems. My car got nice and warm within 3-4 miles and my FBH was NOT working. .. (I had unplugged it).. :D :D
...

Yes, of course you are right. Not essential, but I would guess you would rather have yours working than not:D
Matt

[FrenchMike]

The KBus is a weak point on the FBH and is only used if you want to run the diagnostics using the webasto software. The T4 doesn't like it.

There is a sensor under the radiator that closes at 5 degrees or colder, and will fire the engine up once running. (the 12v comes straight from the alternator)

You can add a switch or remote to fire it up when stopped but you do run the risk of a flat battery if you let it run too long.

HTH

Based on my own experience i would say if the Kbus is disturbed by the PCB ,it PROVES
That the PCB is faulty and then the FBH don't work correctly anyway!

Mike

[goldie75]

Just an update on the webasto.I travelled over 100 miles today,the heating seemed to be working ok[quite cold up here this morning] and the temp gauge was at its usual slightly below the halfway mark but reached halfway a couple of times.Does this mean problem solved? Hope so.....:bowdown: Del

[James.uk]

Once warmed up your guage should read a constant 9 O'Clock, sounds like your thermostat is on it's way out.. :)
...

[Jules]

Just an update on the webasto.I travelled over 100 miles today,the heating seemed to be working ok[quite cold up here this morning] and the temp gauge was at its usual slightly below the halfway mark but reached halfway a couple of times.Does this mean problem solved? Hope so.....:bowdown: Del


Gauge reads in the middle (9 O'clock) between 72 - 118 Deg so you can't go be that!

Run the OBD dash diagnostics 19 log off test No 7 :smilie_re:

http://www.the75andztclub.co.uk/forum/showpost.php?p=479038&postcount=1

[FrenchMike]

Just an update on the webasto.I travelled over 100 miles today,the heating seemed to be working ok[quite cold up here this morning] and the temp gauge was at its usual slightly below the halfway mark but reached halfway a couple of times.Does this mean problem solved? Hope so.....:bowdown: Del

Hi,Del

I think there is misunderstanding ,
Your Webasto stay inactive as long as the external temperature is more
than 5 degrees C.
On winter it only helps your engine to get it's temp quicker :)

Nothing to do with heater/aircon

And i still think your webasto don't work.


Mike

[Matt1960]

Hi,Del

I think there is misunderstanding ,
Your Webasto stay inactive as long as the external temperature is more
than 5 degrees C.
On winter it only help your engine to be hot quicker :)

Nothing to do with heater/aircon

And i still think your webasto don't work.


Mike

Del
Yes I have to agree,
I suspect the fbh may be faulty, and the test will be when it is very cold.
The fbh was there initially to speed up the very slow heating of the coolant, because of the thermally efficient engine.
This is particularly noticable when the temp is freezing or below.

But yours was working when it shouldnt, and this can sometimes mask a faulty thermostat, as the fbh gets the coolant up to 72c, which shows as normal on the guage.
Your coolant should get to 88-89c with or without the fbh, but may be much slower to do this without.
The diagnostics temp will show whether your thermostat is failing, as Jules has said.

Matt

[FrenchMike]

As,already said,

In doubt,one can test the FBH irrespective the external temperature is,
engine stopped ,ignition OFF !

6649

Mike

[goldie75]

Hello again folks.I've just travelled another 900 odd miles in really cold weather and the temp gauge stayed mainly between 8 and 9 o'clock [occasionaly hitting 9 for a wee while]I realise that it should really be sitting at 9 once fully warm.I'm concerned what damage I am doing the car when the tempo not reaching fully 9'oclock.The car seems to be driving fine.Its due a service[prob on Tues] so will get the thermostat checked then.Thanks again Del

[Rammie]

Hi Del,
If your FBH was working, and with the temps where you live, it should be, you would hear it! It sounds like a Tornado Jet Fighter on takeoff!

Also, if you lift the bonnet, and carefully touch the exhaust pipe, and I mean carefully! cos they get extremely hot, this should give you an idea that it is working, as others have commented, I suspect it's not.

I had similar problems to you where the whirring noise was there even when I opened the bonnet or opened a door. The fault was the PCB. I replaced this and since then it has been working fine and warms the car extremely quickly on cold mornings.
Oh, I did disconnect the KBus lead too from the plug.

Hope this is of some help.