On my 98570B later model, that number is on the label which faces you (second line up from the bottom on the left) and on a second label on the end panel which faces out to the wing.

I can confirm shorting pin 3 to ground works on my model, but obviously cannot confirm the method for the earlier one, but it seems safe to assume it is correct - so I will include it.

http://techwebasto.com/heater_main/t...hop/63378A.pdf

Dont know if this is exactly the one on the 75, but certainly looks like it.

This might help as well. You can also find service agents.

http://techwebasto.com/heater_car_light_truck.htm

Quick question.... if you drive for an hour, with the coolant temp 80+, and when you stop and turn the ignition off you can still hear the FBH running, what would this suggest?

Mine comes on and makes a noise, but doesn't appear to actually do any heating...

QUOTE=Jakg

Quick question.... if you drive for an hour, with the coolant temp 80+, and when you stop and turn the ignition off you can still hear the FBH running, what would this suggest?

If the temperature is definately higher than the 77C that the FBH is supposed to turn off at, then I would guess at the FBH being wrongly triggered by activity on the k-bus - try cutting that white/red/yellow k-bus wire.

Mine comes on and makes a noise, but doesn't appear to actually do any heating...

Try the test mode (grounding pin3 on the later model). If it doesn't go through the firing sequence - Running for a few seconds, silent for a few seconds, running again combined with the pump ticking, then the slight roar of combustion, it is probably a faulty PCB. Talk to FrenchMike about a PCB repair.

No problem at all, it is there to be used. :icon_smile:

Thanks - both links now added.

PCB's fine, already sent to Mike.

Will try cutting the K-Bus wire tonight...

I DID get a lot of white smoke when it first got cold though - guessing I need to strip mine down to service it.

Really need to get this sorted at some point!

EDIT - Cut. Will test it when I go out tonight...

When the heater has been running it will still operate after the ignition is turned off this is normal as it goes through a shutdown proceedure where ignition is cut, the internal fan then continues to cool down the burner, when cool enough the FBH will shutdown completely. ;)

Please don't go cutting the K-bus wire with no good reason, if weird stuff is happening to other electric systems then unplug the FBH, your PCB is faulty.

There for a very good reason for the K-bus, it's there for diagnostic purposes, the cars ZCS coding includes the heater, when on T4 and running a diagnostic it will look for the heater via the K-bus if this is cut then it doesn't find it and you won't be able to run a full vehicle diagnostic.

Makes the time diagnosing faults an awful lot longer because then each ECU then needs to be accessed seperately. (the same goes for anything connected to the K-bus, CAN-bus or Nav-bus.)

Russ

D'oh, bit late now... can always reconnect it if needs be. Don't see any T4 sessions in the future though...

PCB isn't faulty (Mikes already checked it).

The problem is that even after driving for hours, with the car running at 80+ (using the inline stat), the FBH will continue running when I park up (no idea if its been running the entire time).

I understand it can run on to cool down... but it shouldn't of been on at all if it'd been hot enough for so long