Fbh
 

After a recent retrofit, my new (to me) FBH fires up like a dream, runs nice and quiet and keeps running for a full hour but does not heat up beyond 48c, in the hour running. I have read it should reach min 74c in approx 20 minutes. Anyone have any thoughts?
The PCB has been to visit French Mike.
Everything appears to operate as it should.
Extremely slow heating up only obvious issue.
Heaters and cooling system fine with engine running.
Thanks.Lee.

I suggest this out of ignorance, is thermostat stuck open in the cooling system?
I know you say fine, how long did car take to heat up before?

macafee2

Inline stat fitted mate. Opens at 87c temp falls to 84/83 then rises again. FBH getting nowhere near opening the stat temp. Thanks. Lee.

Any smoke from the exhaust? The fbh May need a service and a decoke.

It does chuck out some white smoke, not constant but was still same after an hour.Does appear more smokey than Id expect as It's been stripped and serviced I'm told by the seller. I'm assuming it will need to come apart for a decoke is there a How too on here?
Thanks Lee.

This is a good "How to" which I have used successfully.
https://the75andztclub.co.uk/forum/s...d.php?t=205271

This is a good "How to" which I have used successfully.

Thank you for that mate.
Lee.

I bought my car supposedly with a working FBH which I was unable to use due to the billowing clouds of white smoke emanating from the exhaust and of course it wouldn't get up to any sort of heat.

The boys in the Midlands sorted it out for me after describing it as the most coked up, sooted up one they had ever worked on.

Unfortunately when refitted there was still loads of white smoke emitting from it caused by the fact that the exhaust / silencer was also chock a block full of soot which meant that the exhaust had to be exchanged for a new/2nd hand one.

Once that was changed it has worked perfectly with no smoke coming out at all when it is on.

So it might well be that your exhaust is also sooted up and needs cleaning out before you are able to get rid of the white smoke and get full operation from the FBH.

If it is running nice and quiet for a hour, then it is only idling, because it is up to what it believes is about 79 -85c, and is keeping it running at 48c. You more than likely have a thermo sensor problem, and need to try another PCB

Lee, i believe there is a thermal measuring component on the PCB which judges what temperature the water has reached, possibly it is not working correctly, or part of the measuring circuit is suffering with the corroded resistor issue.

You might find a mmber with one of the webasto test boxes which might tell you what the heater thinks it is doing. I would guess the heater thinks the water is at the required temp but in fact it is not, as your car is telling you.

The other thing to check is if the FBH supplied actually did come out of a 75, and not out of a different application. These things are fitted to all sorts of cars, boats and other stuff which maybe should work at lower temperatures.