Webasto fault finding

[weegaz22]

Hi guys, i have a webasto DBW46 fitted to my van and it wasn't working when i bought the van it off the previous owner, I am in the process of attempting to fault find the issue/issues and was wondering if i could get some tips, so far i have taken the end cap off the webasto and found there is no fuel getting to it, so took i took off the fuel dosing pump off and checked that it was pulsing by connecting 12v across it, that soleniod pump seems to works fine, i re-installed it and changed the fuel pipe T piece orientation as the way it was would was pointing up and would end up causing an airlock,now it is gravity fed and not trying to pull fuel uphill, again i tried turning webasto unit on and nothing happening from fuel pump side, the glow plug doesn't seem to attempt to get warm, the only thing that happens is the relay next to the webasto control unit triggers and the blower motor comes on, the display itself also looks corrupted so am i looking at a new control unit and display? i also disconnected all the plugs from control unit and display still looked corrupted like in the pic below


So, any of you webasto guys know what the hell my problem is?? cheers in advance

[scottbott]

oldiebutgoodie is your man to ask for these sort of problems

[Oldiebut goodie]

I don't deal with the water heaters but,
Are you following what the start up sequence is doing from the manual. It is no good stabbing wildly in the dark at possible errors, actual failure point must be noted to achieve the correct diagnosis.

[weegaz22]

Cheers oldiebutgoodie, that will give me something to start from, i will no doubt get back to you once i establish what is or isn't happening

on figure 3.1.1 i take it to "turn it on" you press the little flame button? never used a night heater before so i'm assuming that's how it is turned on

[Oldiebut goodie]

Yes.
Do you have the manuals? You will need them if you want to do anything at all with diagnosis. PM me your email address if you want copies.

[weegaz22]

Yes.
Do you have the manuals? You will need them if you want to do anything at all with diagnosis. PM me your email address if you want copies.

manual(s)? there is only one that i have and its this one

http://fourbyfourclub.com/Manuals/BBW46RepairManual.pdf" onclick="window.open(this.href);return false;

My email should be in my profile info

[Oldiebut goodie]

That is as good as you can get - the others that I have are the installation and service parts ones.
Pay attention to the timing of the failure point and check against the manual.

[weegaz22]

ok, had a look today, looks like i am getting stopped at glow plug activation stage, the circulation pump runs but the glow plug does nothing, i took the glow plug connector off the back of the glow plug and it is getting 12v to the plug, but glow plug does nothing, BUT if i connect the glow plug to a 12v supply it glows in a few seconds, glow plug resistance is 1.5 ohms, it will just sit there running in that stage till i turn it off

[Oldiebut goodie]

How do you know that the glow plug does nothing? Are you running it with the glow plug outside of the heater? 1.5 ohms seems a little high - with those type of glow plugs I would expect around 0.8 ohms. What is the resistance across the fuel pump terminals?(disconnected)
Check the resistance of the flame sensor also. Also check that the voltage isn't dropping below 10v at the heater whilst the glow plug should be glowing.

4.5 Kw is a bit OTT for these little vans, I am surprised that your van has one unless your van came from colder climes like Finland, Norway etc. I know that it was factory fit upon request. They aren't really a night heater more a travelling one.

[weegaz22]

How do you know that the glow plug does nothing? Are you running it with the glow plug outside of the heater? 1.5 ohms seems a little high - with those type of glow plugs I would expect around 0.8 ohms. What is the resistance across the fuel pump terminals?(disconnected)
Check the resistance of the flame sensor also. Also check that the voltage isn't dropping below 10v at the heater whilst the glow plug should be glowing.

4.5 Kw is a bit OTT for these little vans, I am surprised that your van has one unless your van came from colder climes like Finland, Norway etc. I know that it was factory fit upon request. They aren't really a night heater more a travelling one.

I have the end cap off where the burner fleece goes from when I was trying to diagnose if it was getting fuel in through the end cap fitting, glow plug is still in the body of the heater

Van is a German import
Fuel pump resistance is 10.3 ohms

I'll get back to you on flame sensor resistance, vans all locked up for the evening, crawled under it to get fuel pump resistance, when you say check its not dropping below 10v at the heater is there a particular pin/wire colour i should be checking? iirc i think it does 9 something volts at the glow plug but i think thats for the sampling part, it then jumps to 11.5 or there abouts

[Oldiebut goodie]

Take the voltage between the power going to the ECU and one of the brown earth connections on the heater.
The fuel pump resistance is fine.
BUT:
Just thinking about this heater - you have no manual temperature control for it and it runs when the coolant temperature is low enough. At present temperatures the temp will be far too high for the heater to operate! I have a feeling that they do not start until the temp is something silly like 5 degrees C.... might be higher, I can't find any reference to temp control other than what the temperature sensor in the coolant does.
You may have to wait until winter to see if it works. ( you may be able to fool it into firing up by replacing the coolant temperature sensor with a resistor around 750/800 ohms which would make the heater think that it is around 0 degrees - that is what I would try anyway)
As I said, I don't work on the coolant heaters at all so I am not au fait with them.

[weegaz22]

Take the voltage between the power going to the ECU and one of the brown earth connections on the heater.
The fuel pump resistance is fine.
BUT:
Just thinking about this heater - you have no manual temperature control for it and it runs when the coolant temperature is low enough. At present temperatures the temp will be far too high for the heater to operate! I have a feeling that they do not start until the temp is something silly like 5 degrees C.... might be higher, I can't find any reference to temp control other than what the temperature sensor in the coolant does.
You may have to wait until winter to see if it works. ( you may be able to fool it into firing up by replacing the coolant temperature sensor with a resistor around 750/800 ohms which would make the heater think that it is around 0 degrees - that is what I would try anyway)
As I said, I don't work on the coolant heaters at all so I am not au fait with them.

Surely if you have the option to manually turn it on it will just run up till its max operating temp then shut off rather than requiring a minimum temp?

apparently these were also installed in land rovers and i haven't really seen anyone mention or say it needs to be X temp before it will actually turn on, just press switch on dash and it will run till it hits its temp limit.

any reason why i would be getting 12v to the glow plug's end connector but not getting any actual glowing? does nothing when connected to GP loom but glows like nobody's business when connected to a 12v battery. duff plug?

[Oldiebut goodie]

You could be getting 12v at the glow plug during the component check phase but you are not getting current flow at the full 16A for the glow operating. As I have said twice - I don't work on the coolant heaters so I don't know.

[weegaz22]

You could be getting 12v at the glow plug during the component check phase but you are not getting current flow at the full 16A for the glow operating. As I have said twice - I don't work on the coolant heaters so I don't know.

the flame sensor reading i am getting is 2.94 on the multimeters 20k resistance setting, is that within a spec you would expect? i realise you don't work on these, but you are the only person i can talk to that has any understanding of how these kind of systems of work, i am fairly unfamiliar with them so just because i am asking "why" about something i don't mean to come across rudely as expecting you know or to diagnose it, i am just trying to figure out where mines is failing

[Oldiebut goodie]

If it is like the flame detector used on the HL32/Airtop32 I would expect to see around 10000 k ohms + ie effectively close to infinity this dropping to the region of 70 to 90 k ohms when heated to cherry red. From the manual it appears to be the same type. Check yours by observing that the resistance drops considerably when heated to cherry red.
I presume that you have checked the temperature fuse for continuity and also the temperature limiter.
You will need to check also that the temperature sensor for the coolant is within the range in the manual.