old webasto dbw 46

right maybe someone can help, I have an old webasto dbw 46 came with my defender 90 (ex-mod winterised). Ive got the manuals off the internet tried what it says and im getting nowhere.

Heres what ive done so far:
when I got it switch it on no light nothing, I traced the wiring and found some corrosion on the wire to the switch, chopped that out replaced it and switched it on.

Nothing. so went on to look at the webasto control unit opened it up found 2 dead resistors 1 capacitor and a voltage regulator replaced them, switched it on.

no light on the switch (possibly just a dead LED), air fan came on immediately for 60 sec then went off. Checked the temperature sensor showing about .800 ohms, checked input voltage 12.5v, stripped the heater checked: the water pump seized (stripped cleaned and reassembled fine), fuel pump fine, air pump fine, heater felt fine. Fitted an new glow plug put it all back together switched it on.

Now the circulation pump runs for 2 seconds then the air fan kicks in again for 60 seconds, convinced it was the control unit I managed to source another unit from Germany. Guaranteed as working but used got it plugged it in switched it on.

Same, circulation pump runs 2 seconds then the air pump kicks in for 60 sec. So I've turned my attention to the temperature sensor and ordered another but from a thermo top (its the same but with a different connector). Is this the right move? or am I chasing my tail, should I just give up and admit it will never work again

thanks

It's normal for the fan to come on at the start of the cycle to clear any fumes/ vapour from the previous cycle, after that, the ignition cycle should commence followed by the fan, circulating pump and fuel pump.
I'm not familiar with the model you quote but the general sequence of operation is the same on all of them.
Ignition glowplug failure is common as is the flame detector.
http://www.telusplanet.net/public/gary2a/rack/bbw46/bbw46.pdf

Hi datatek,

Yes that's one of the manuals I've downloaded there's no mention of the fan on startup on any sequence apart from trouble shooting, I've left it for a few minutes after the initial run and it does nothing like its lying dormant

apeers said:

Hi datatek,

Yes that's one of the manuals I've downloaded there's no mention of the fan on startup on any sequence apart from trouble shooting, I've left it for a few minutes after the initial run and it does nothing like its lying dormant

Click to expand...

Does the fuel pump work? Long time since I've touched one but they work a bit like a pressure jet burner in a domestic heating boiler if they run on diesel, fan on, glow plug on, start fuel pump, bang off it goes.
they were always trouble on boats, the gas fired ones were much less trouble.