Webasto Heat - Where to start?

[Tim Good]

Check voltage at the heater when you attempt to start. If it drops below 11.5v ?? then it wont start
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My Webasto dates from 2000 and faults show up as errors by flashing lights on the control, which might indicate low voltage or fan failure etc.

Ok interesting.

so I plugged into shore power and put the charger on to give it a little extra voltage help. It draws about 20 amps and then stops and switch flashes quickly and then gives 3 long flashes which = Voltage low / voltage high warning. I'm sure it isn't too high as too high would be 15v + according to a PDF I found. I haven't discovered exactly what model it is but it heaters air and water.

I took a voltage reading at the junction box near to it and it reads what the batteries are... about 13.5 at charge. There is then only 30cm of cable going to the unit so there couldn't a be huge voltage drop between there and the unit surely?

Here are some photos. Ignore the water hose.

 

[David2452]

It's an old DW80 boiler, as I suspected due to the mention of multiple thermostats. I have a PDF workshop manual if you want to PM me an email address. There is no overvoltage cut out for this heater but three flashes are under voltage, check the power connection at the ECU (whilst trying to start otherwise readings are meaningless) and clean the connections on the power to ECU plug as a start. The ECU is the thing in your photo with the A,B,C, E & F plug markings on it. 20a seems a lot for this heater to be drawing as it is a ceramic pin and not the old fashioned coil type.
BTW, this boiler has a cut out voltage of 10.25v so you either have some pretty high resistance in the terminals or cable or an ECU fault, the fact that it is able to draw 20a is a bit odd though.

 

[Tim Good]

It's an old DW80 boiler, as I suspected due to the mention of multiple thermostats. I have a PDF workshop manual if you want to PM me an email address. There is no overvoltage cut out for this heater but three flashes are under voltage, check the power connection at the ECU (whilst trying to start otherwise readings are meaningless) and clean the connections on the power to ECU plug as a start. The ECU is the thing in your photo with the A,B,C, E & F plug markings on it. 20a seems a lot for this heater to be drawing as it is a ceramic pin and not the old fashioned coil type.
BTW, this boiler has a cut out voltage of 10.25v so you either have some pretty high resistance in the terminals or cable or an ECU fault, the fact that it is able to draw 20a is a bit odd though.

Thanks. yes pleas eon the manual. I'll PM you my email. Don't quote me on the 20amp as thats a rough reading from the ammeter on my switch board. Trouble is I can't get from the panel in the saloon and into the lazarette locker (literally in it) within 15 seconds which is the time it takes before it stops drawing current and switches to the error flashing code.

I'll clean every terminal I can and see what happens also also try and run the engine next time to boost the voltage. I'll report back!