Webasto problems (winter drawers on!))

[broadnorfolk]

I've got an ageing Webasto warm air system fitted which I have managed to partially resurrect (by scrubbing contacts clean) from complete no go to doing everything but heating air. When I wind the switch round to 'start' it ticks away merrily, the yellow light comes on ok, then the fan starts up, but I'm getting no combustion (or green combustion light).

When it ticks round to full heat the fan cuts out - I'm guessing there's a thermocouple in there somewhere to stop it running without combustion (?). The plug seems to be heating up (hot to touch from outside), though I'm wondering whether this is just due to electrical resistance.

I also notice that there is a drip of diesel from underneath the unit when the combustion sequence should be starting - is this meant to happen? I'm guessing it is the unburnt diesel running out from the combustion chamber.

So theories so far are either that the plug isn't heating up, or that there is a leak in the diesel line inside the unit and the fuel isn't getting to the plug.

I did read in another post that the old systems might need the engine running up to start them, so I'll try that and then a new plug

Any other suggestions?

 

[VMALLOWS]

I don't know the Webasto specifically, but believe it is very similar to Eberspacher.

From your symptoms it sounds as if it simply isn't igniting within the maximum time allowed, or before the voltage at the control unit drops before a low-voltage threshold. I have had the latter problem several times due to either the battery being low, or high resistance contact in the supply fuse to the heater. In these cases starting with the engine running will often raise the voltage enough to get it to fire. The easiest way to check would be to measure the voltage at the glowplu during the start-up. It should be a bit lower than the voltage at the battery, but not lower than, say, 11v. I note you've had contact problems and it may be that there's still a high resistance somewhere.

On the Eberspacher, the sequence won't start at all if the glo-plug is open circuit (or the over-heat switch has tripped, but can't be certain for the Webast./

 

[Footpad]

Had a similar problem with our ancient Ardic (Volvo) and was recomended to try starting it with the engine running as above and it did the trick. However we discovered other problems with fumes which appeared to come from leaks in the heat exchanger so I am now fitting and Eberspacher - See Jeremyf's post "Diesel Heating"

 

[david_bagshaw]

Most common prob with the ebersp.. is the heater plugs burn out, is there a heavy current load as it tries to start?

put hand on plug casing, it should get more yhan warm

otherwise , does the webasto also have a high voltage sparker as well, as that might be the prob.

good luck

David
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[ChrisP]

There is indeed a switch that detects the flame has been established. On the older models its a micro switch mounted on a bi-metalinc well. The post inside the well expands and causes the switch to operate. Without the switch operating the cycle is terminated at the end of the warm up period. The switch is mounted to the detector assembly with screws in slotted holes. I had the same trouble with my unit sometime ago. Readjusted the switch position and away she went. I tested and repaired the unit on the bench at home it was easier than plying fruit bat on the boat. If the switch it's self is knackered hunt around your local industrial switch suppliers for a replacements. They are often used to indicate the positions of valves and machinery parts. The replacement from Webasto is almost the same as the cost of a new unit

What do you mean the sea gull in front's walking !!!

 

[Chris_Robb]

I have a 25 year old Webasto, and I have a similar intermittent problem, and have traced it to the following:

When the unit is started, the glow plugs take approx 40 amps. At the point when the fan kicks in, I measured the voltage at the electric diesel pump, and this had dropped to about 7 volts, so did not pump up diesel. (sysmptom was no smoke at exhaust).

By running the engine, the battery voltage reached 14.4 and the voltage at the diesel pump was raised to 11, and it started pumping. evidenced by large volumes of smoke from the exhaust.

Even then it would rarely start 1st time, and would shut down. Normally it would start 2 time.

The high ampage of the glows seem to drain all the voltage leaving the pump with bugger all.

I take note of one of the postings that says you can adjust the shut off bimetal valve, which may be a contributory problem.

Once going, it chucks out the heat, but it really does consume battery power, so is used only when I know I can bring the batteries up again, as she lives on a mooring.

 

[broadnorfolk]

Re: Webasto update (brown trousers on!)

Thanks for the replies - there's good news and not so good news...

Tried starting it with the engine running, but no go - voltage at plug down to about 4, so had another look behind the switch panel for any contacts I'd missed.

Found a rheostat behind a cover which was looking fairly scuzzy, so pulled it apart and scrubbed all the contacts clean, then had another go. Bingo; yellow light, fan, green light, go!

Then it all got a bit scary...

About ten seconds after the combustion light came on huge clouds of smoke starting pouring out of every hole and connection on the unit, so I cut off the power and the diesel sharpish and grabbed the nearest extiguisher, as (presumably) years' worth of accumulated diesel gunk went up in one go. Thankfully things died down after a bit and all eventually cooled down, but I think a service may be required before trying again.

On the other hand it could just be a trip to B&Q for a fan heater...

Thanks again for the help with this.

 

[david_bagshaw]

Re: Webasto update (brown trousers on!)

give it another go, as soon as it lights , shut off the fuel, let it run it self out, then reconnect fuel and go again.

think how gooey it is in there after all the failed starts. may be the over temp switch will have tripped, if fitted.


good luck

David
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