Webasto Thermo Top C Fuel does't ignite unless engine is running.

SoulFireMage

SoulFireMage

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Morning all,

We're back again with a new question for anyone into Webastos?

This problem has been getting worse during the course of this week.

First, we always have to start the engine to get the heater to ignite, when we first got her this wasnt the case.

Second, it shuts down despite having no thermostat attached after a while. When it first did this it was after about 2 hours but this time is steadily decreasing and this morning it died after ten mins.

We checked coolant levels and the fuel tank is full.

One thing I've realised as I'm trying to type this on a mobile device, is that it may be as simple as the unit is connected to a battery that is going flat, separate from the circuit that the shore power would charge. But the engine still charges that battery when running.

Any thoughts?
 
If I get you right, "the unit is connected to a battery that is going flat, separate from the circuit that the shore power would charge" you certainly have pointed out a possible cause.

Heaters need power - both volt and amps - and will cut out if supply is too low. Some models even contain a circuit to cut out before absolute minimum, to leave you a chance to start the engine (when on same battery). Your heater is rated for 42 watt consumption. Given a 12 volt battery this calculates to 3.5 amps. Connected to a battery of say 60 AH (ampere hours), it will drain the source in (60:3.5=17,5) hours theoretically. In practise this will vary as the consumption is not static and the burner will cut out if voltage range is not 10.5 - 15 v.

At the end of the day you need to charge the battery driving the heater at a rate that will allow battery capacity to stay at 100% even with the burner running. This way you will have full power on tap even when not on shore power.

A good (so called intelligent type) charger will cope and allow being connected at all times because it switches to 'maintain' mode when battery is fully charged.
 
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Possibly a battery charging issue, in fact it is the most likely suspect, but not the only one, simple to check though, the TTC power requirements are not huge but they do need a bit, sadly. unlike the Airtop range, the Thermo Top C has no diagnostic lights and needs to be hooked up to Thermotest software so I can't even ask for a flash code. Another possibility is that the fuel system is installed wrongly and it needs the suction from the motor to pull the fuel up to the point where the fuel is taken. Proper install is direct from the tank. A proper marine TTC has a much lower cut out voltage than a vehicle one so check the label, if it doesn't say Motor home or Narrowboat on the label then it has been fitted with a vehicle unit which has different parameters where the heater is designed to run for only and hour maximum before the engine is started. BTW, the cut out voltage for Webasto marine grade heaters is 10.5v, vehicle ones are much higher to protect the usual arrangement of running them from the starter battery.
 
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Which Battery?

SoulFireMage said:
Morning all,

We're back again with a new question for anyone into Webastos?

This problem has been getting worse during the course of this week.

First, we always have to start the engine to get the heater to ignite, when we first got her this wasnt the case.

Second, it shuts down despite having no thermostat attached after a while. When it first did this it was after about 2 hours but this time is steadily decreasing and this morning it died after ten mins.

We checked coolant levels and the fuel tank is full.

One thing I've realised as I'm trying to type this on a mobile device, is that it may be as simple as the unit is connected to a battery that is going flat, separate from the circuit that the shore power would charge. But the engine still charges that battery when running.

Any thoughts?
Click to expand...
Acouple of years ago we had a similar problem with a hired canal boat. It turned out that the Webasto was fed from the engine start battery not the domestic bank. Apparently this was because if wired in to the domestic bank it was prone to cut out when the inverter was used and lowered the voltage.
On our own boat the shorepower only charges the domestic relying on the engine to charge the starter battery so connecting the heater to the starter battery would be a recipe for disaster.
With a baby grandson on board and a very cold Easter we tried to run the heating overnight on the canal boat with the same result in the morning, no heating and no engine.
 
Thank you guys, I'll start with the battery then once its late enough that we won't be waking up a dozen narrow boats around us with the engine. The battery voltage is 10.5 which I think partly been caused by a fridge - an isotherm - that is 12v only that we didn't realise wasnt on the shore power.
 
I was going to post as above but it's all been said I think. I would only add that anything under 11 volts equals a flat battery anyway! It may well be that you simply have a knackered battery that won't hold a charge. Before you look for more complicated solutions, get it tested. A replacement these days is not expensive.
 
In your case it does sound as if it's the battery at fault but exactly the same can happen as a result of poor supply, maybe some corrosion in a connection somewhere. My Eberspacher has had exactly the same problem, would only run while the engine was running, even though my batteries are relatively new and in good condition.
 
SoulFireMage said:
Thanks guys, again :) I think we have it now. Battery, the simplest answer!
Click to expand...

Why is it the simplest answer? You suggested in your original post that the shorepower charger might not be connected to the battery which supplies the heater. Shouldn't you check whether this is the case before doing anything else?
 
We've had her ten days, haven't had a boat for seven years and were no experts then. So I hadn't twigged how the charging system worked and also hadn't thought a diesel heater needed current during operation.

So the battery being flattened whilst we were on shore power was unexpected to us, though obvious in retrospect!
 
You might look your setup over before deciding, to ensure you calculate and estimate right.
The charger at hand may well be able to cope as is, even if you change your battery layout and the current battery could well be OK if recharged carefully.

Start by adding up all consuming devices' nominal wattage. Then estimate the use of the devices to get the net power needed and the charger capacity to meet it within time available at shore power.
Battery banks' size must match, too.
 
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