Webasto Diesel Cooker - blowing fuses

[Winchweight]

Hi,

I fitted the cooker about 2 years ago and it’s been brilliant. But last weekend I tested it and it was fine, but my wife went away in it and came back saying the cooker has no power. I checked the fuse and it was blown.

So I replaced the fuse and tried again, but although it began its cycle, as soon as the fuel pump should have kicked in, the fuse blew again. I then checked all the wires from the battery up to the cooker, then removed the cooker and checked the wires on the circuitry and to the pump for chaffing etc, but all was good.

I surmised that the fuel pump might be seized, so I disconnected everything from it, then applied 12v directly to it and although it lurched slightly, it didn’t begin running. The pump is like the diaphragm pumps for a Webasto or Eberspacher heater, albeit smaller. Was this a fair test and is the pump knackered?

How else can I test it and where can I get a replacement pump as the t’interweb comes up with heater repair centres, but not cooker centres?

[Oldiebut goodie]

The pump runs via pulses the same as heaters. Applying 12v will only give you 1 click, you have to tap the voltage across the terminals. It would be odd that a pump blows a fuse, the ecu should sense that it is out of its parameters then shut down operation.
Do you have a blinking fault code? Which fuse is blowing?
I would focus on combustion air fan or glow plug.( maybe ventilation fan also)
I would work through the workshop manual rather than just jump in at odd points of the start up sequence. The manual gives you the details on the flash codes.

[Oldiebut goodie]

PS....No diaphragm in heater pumps:

[Winchweight]

Hi, the fuse is the 15a fuse. Initially it would begin the ignition sequence then blow without the pump running, but it now blows almost immediately without the ignition sequence starting. This is why I thought it would be the pump. There’s no fault code as the fuse blows before I get to see it.

I saw the ventilation fan running but didn’t notice the combustion fan running. Also didn’t look at the glow plug. I’ll look at both next weekend.

[Oldiebut goodie]

My first suspicion would be that the glow plug is shorted. Then combustion fan.

[Winchweight]

Thank you. I’ll get one in and if it isn’t I’ll have a spare. I know that Tigger Travels had a flow plug failure too.

[lloydy]

an easy test i would try is unplug the pump and let it go through the cycle. The cooker wont know the pump is unplugged, if the fuse doesnt blow its the pump. If it does blow then move onto the glowplug, then fan. Its just a process of elimination

[Winchweight]

Thanks Lloyd. Good idea.

[lloydy]

basically thats what i do on heating systems that are taking out fuses.

[Oldiebut goodie]

Oh yes it will know that the pump isn't connected. The ecu will check if the pump is connected upon switch on - as normal. If no connection it will not see the resistance thus will not start.

[Winchweight]

Oh... ok.

OBG - do you have a reliable source for a glow plug?

[Oldiebut goodie]

Try Stuart at http://www.melloronline.co.uk ( he is usually willing to help over the phone, I used to have an account with him but not any more) - list price is £43 odd + vat though, not the sort of thing that you replace on a whim. I would take the glow plug out and connect it to a fused 12v - tip should glow within 20sec if good. If shorted it should blow the fuse.

Webasto part no. is WA853513

[lloydy]

i bow to you superior knowledge on these units. unusual for a two wire pulsed supply to recognise resistance though? normally for that you would have permanent 12v supply then a 0-12v for speed which would recognise resistance

[Winchweight]

Try Stuart at http://www.melloronline.co.uk ( he is usually willing to help over the phone, I used to have an account with him but not any more) - list price is £43 odd + vat though, not the sort of thing that you replace on a whim. I would take the glow plug out and connect it to a fused 12v - tip should glow within 20sec if good. If shorted it should blow the fuse.

Webasto part no. is WA853513

Thank you.