Troubleshooting a Webasto Air Top 2000 STC with MultiControl

[Tedd]

Troubleshooting might not be the right word as I'm not looking for tips on troubleshooting, per se, but rather hoping someone here as had a similar experience with the same model and can provide advice.

My installation is brand new, in a new boat. Unfortunately, I'm 4,500 km from the dealer who installed it and so can't easily go back to them for a warranty repair. The heater has never worked since I got the boat home. The dealer says it worked when I bought the boat, but it was summer and I neglected to properly test it.

Here are the symptoms.

Sometimes--randomly, so far as I can tell--the heater starts up and runs normally for a few minutes, then stops with a fault code F15. I have various documents that describe this code in different ways but they all seem to suggest either a sensor that is open circuit or a sensor that is short circuit.

Other times--again, with no pattern I've been able to discern--it simply fails on start up and reports error code F89. That code doesn't even appear in the any of the documentation I've been able to find.

I have visually checked all of the wiring that is readily accessible and opened and examined all of the connectors. I've primed the fuel system and ensured that flow is reaching the burner unit. And I've pulled and reinstalled the fuses. None of that has changed the behaviour in any way I can observe.

So... help!

[steffan]

I have a Planar, not Webasto, but the dosing pump on mine failed very early on. It still made the ticking sound like it was moving fuel but was in fact, not. Replaced.

I found that running the fuel line through too tight a radius near connections introduced tiny air bubbles that would eventually shut it down with a code. Re-routed.

If it's been sitting unused for a while it generally takes two startup cycles to not throw the 'fail to start' code that is maybe your F89. Accepted and moved on

Sorry, that probably doesn't help much. Hope you get some specific help.

[Tedd]

Thanks, steffan, that's a big help. The times the system has worked (temporarily) I felt that the pump sound was odd, i.e., not what I expected. So, I'll definitely follow that idea.

I also noticed when I ran the pump into a pail that the flow rate was very low. I'm just guessing here but it would be something like a few ml a minute, maybe even only one ml per minute. But I had no way of knowing whether or not that was normal. Obviously, the fuel consumption rate of the burner is very low but I was expecting a more vigorous free-flow rate from the pump.

[Tedd]

Next step: I raised the fuel tank about a meter above the Air Top unit (as far as the hose would allow) in an attempt to get gravity to help the flow rate. The free flow rate into a pail was still very slow and the symptoms remained the same. It ran 8-9 minutes and then shut down with an F15 fault code.

I will investigate the specs on the pump to see what the flow rate should be.