Webasto thermo top C problem

[steviehat]

Hi Everyone, my (refurbished) Webasto thermo top C seems to have a problem. It usually doesn’t start tho I have had it running a few times and it’s great but has never worked twice in a row.  Lately it has refused to start altogether because the fuel pump isn’t clicking . I bared the fuel pump positive lead to test it and it works fine. If I tap it against the positive battery terminal i can see the fuel moving through the (temporary)  transparent fuel pipe and even get the unit to fire up whilst doing this but when I stop, the fuel stops and of course it shuts down. . Have checked the continuity between both ends of the pump wiring harness and its fine but there’s no voltage pulse from the unit to the pump. The batteries are good and voltage is 14v when the sun is out. 
Have tried all the restart/ on,off /5 seconds/ fuse out bollox and now i’m all out of ideas and considering abandoning it and putting it down to ( a bad ) experience. 
Shame coz this is the time of year when we could do with using it because it’s cold in the mornings but not cold enough to put the Rayburn on…and it’s cost me about £800 up to now..Argh !!

Can any clever person think of anything I’ve not checked ?

Cheers  

[MtB]

9 minutes ago, steviehat said:

The batteries are good and voltage is 14v when the sun is out. 

 

As in the other thread, battery voltage is only half the story. Supply voltage at the end of the wires feeding the Webby is just as important.

 

Have you measured it during the start-up sequence? If supply voltage on the input terminals  is low (i.e. below say 12.5v, and possibly due to thin wires or poor connections) this could easily be messing up the PCB process driving the fuel pump. 

[PeterF]

I had an erbespacher and the fuses had some surface tarnishing from dampness that caused a voltage drop and cause.d failure to start. Swapped them, cleaned the fuse holder and bingo. Just something to check perhaps.

[Alan de Enfield]

46 minutes ago, steviehat said:

Hi Everyone, my (refurbished) Webasto thermo top C seems to have a problem. It usually doesn’t start tho I have had it running a few times and it’s great but has never worked twice in a row.

 

Is it a 'refurbished from a cheapo ebay seller' ?

 

These are generally automotive units refurbished and sold to buyers that are ignorant of the fact that the electronics for automotive units are different for the marine / boat version.

 

Automotive batteries are always pretty much 100% charged and will be presenting 12.7-12.9v to the 'webby' - boat batteries are generally at a much lower state of charge - typically 12.1v - 12.5v, and only occasionally will be at 12.7-12.9v.

The electronics on the marine version has to be re-programmed to work on lower voltages.

Apparently other changes are also necessary

Source :- a Webasto agent that used to be a member here.

 

Your 14v 'when the sun is out' is NOT your battery voltage, it is simply the 'surface voltage' - what is your battery voltage 1st thing in the morning whilst it is still dark ?

Edited September 25, 2021 by Alan de Enfield

[steviehat]

1 hour ago, MtB said:

 

As in the other thread, battery voltage is only half the story. Supply voltage at the end of the wires feeding the Webby is just as important.

 

Have you measured it during the start-up sequence? If supply voltage on the input terminals  is low (i.e. below say 12.5v, and possibly due to thin wires or poor connections) this could easily be messing up the PCB process driving the fuel pump. 

Sorted! That’s exactly what it was. Just wired it directly to the batteries rather than via the switch panel. That extra three meters must have caused the voltage drop. Thank you SO much !

[MtB]

1 minute ago, steviehat said:

Sorted! That’s exactly what it was. Just wired it directly to the batteries rather than via the switch panel. That extra three meters must have caused the voltage drop. Thank you SO much !

 

👍

 

Excellent news, thanks for the update!

 

Where do we send the bill? 😁

[steviehat]

1 hour ago, Alan de Enfield said:

 

Is it a 'refurbished from a cheapo ebay seller' ?

 

These are generally automotive units refurbished and sold to buyers that are ignorant of the fact that the electronics for automotive units are different for the marine / boat version.

 

Automotive batteries are always pretty much 100% charged and will be presenting 12.7-12.9v to the 'webby' - boat batteries are generally at a much lower state of charge - typically 12.1v - 12.5v, and only occasionally will be at 12.7-12.9v.

The electronics on the marine version has to be re-programmed to work on lower voltages.

Apparently other changes are also necessary

Source :- a Webasto agent that used to be a member here.

 

Your 14v 'when the sun is out' is NOT your battery voltage, it is simply the 'surface voltage' - what is your battery voltage 1st thing in the morning whilst it is still dark ?

No it was refurbished by  a marine specialist but your right coz I just wired it directly to the batteries and now it’s totally fine. Must have been the voltage drop between the unit and the switch panel. Thanks 

1 hour ago, PeterF said:

I had an erbespacher and the fuses had some surface tarnishing from dampness that caused a voltage drop and cause.d failure to start. Swapped them, cleaned the fuse holder and bingo. Just something to check perhaps.

Yeah I tried that too. Made no difference but worth a go. Thanks 

[steviehat]

2 hours ago, MtB said:

 

👍

 

Excellent news, thanks for the update!

 

Where do we send the bill? 😁

I’ll set up a direct debit to pay you every morning when we switch it on !

[MtB]

1 hour ago, steviehat said:

I’ll set up a direct debit to pay you every morning when we switch it on !

 

Excellent, thanks! I'll post up my bank details here shortly. 

 

Oh, hang on...!!!!!

[Tony Brooks]

21 hours ago, steviehat said:

No it was refurbished by  a marine specialist but your right coz I just wired it directly to the batteries and now it’s totally fine. Must have been the voltage drop between the unit and the switch panel. Thanks 

 

 

What's your domestic master switch like? If it has a removable plastic key, that might be your problem but more likely undersized wirirng.

[blackrose]

Jumping on the back of this thread, I've just filled up my C/H system with antifreeze. Does anyone know if there's a coolant bleed screw somewhere on the Thermotop C? I can't see an obvious candidate and there's nothing in the installation manual to guide me.

[blackrose]

Having looked at some other threads I can see there is no bleed screw on the unit. That does seem odd. Webasto expect you to bleed the heater of air in the coolant lines by either taking off pipes and running the pump or fitting your own bleed valve somewhere near the heater. Why didn't they just design the heater with a simple bleed nipple?

 

Checking the coolant level in my header tank I seem to have lost about a cm overnight. Just wondering if that's air in the heater and pipes being gradually displaced or I've got a leak somewhere? All the C/H rads were well bled yesterday.

[Tracy D'arth]

17 minutes ago, blackrose said:

Having looked at some other threads I can see there is no bleed screw on the unit. That does seem odd. Webasto expect you to bleed the heater of air in the coolant lines by either taking off pipes and running the pump or fitting your own bleed valve somewhere near the heater. Why didn't they just design the heater with a simple bleed nipple?

 

Checking the coolant level in my header tank I seem to have lost about a cm overnight. Just wondering if that's air in the heater and pipes being gradually displaced or I've got a leak somewhere? All the C/H rads were well bled yesterday.

Contraction on cooling? Approx 4% from ambient to 80 degrees. 

[blackrose]

49 minutes ago, Tracy D'arth said:

Contraction on cooling? Approx 4% from ambient to 80 degrees. 

 

It's still ambient. I haven't started the heater yet. Waiting for a few bits to arrive to finish the fuel line installation.

 

I'll just see if the level continues to fall.

Edited September 27, 2021 by blackrose

[Tony Brooks]

Do you have any plastic pipes on the heating system? If so and if you have used any compression fittings then at the very least you need metal, rather than plastic pipe inserts, and they still may leak as the plastic softens and creeps away from under the olive.

[blackrose]

45 minutes ago, Tony Brooks said:

Do you have any plastic pipes on the heating system? If so and if you have used any compression fittings then at the very least you need metal, rather than plastic pipe inserts, and they still may leak as the plastic softens and creeps away from under the olive.

 

Yes I do and I have some compression fittings. I see what you mean about the plastic pipe inserts. To be honest I can't remember what type of inserts are in all of those joints. However, they never leaked before over the 4 years I had an Eberspacher connected to the system, but the C/H system hasn't been filled for about 12 years so I knew that if it didn't leak somewhere it would be a minor miracle. 

 

I have some compression fittings within easy reach and they are bone dry so hopefully the rest are ok. But I'm sure I've used plastic inserts/compression fittings in my domestic fresh water system and 16 years on they're all still fine.

 

I'm still hoping the antifreeze is displacing air in the heater and that's why the level has fallen - but I may be clutching at straws. It's going to be a pain to get to every joint in the C/H system to check it. The 50% of it that is readily accessible is dry and none of the rads are leaking. 

Edited September 27, 2021 by blackrose

[Tony Brooks]

On mine, the problem one was on the full bore valve that I used to isolate the rads from the boiler for summer water heating. I don't think having a lever on the valve helped.

[blackrose]

The coolant level seems to have stabilised and isn't dropping in the header tank now. I think it must have been finding its way into the heater and displacing/slightly compressing the air in there? I'll bleed the heater once it's up and running.  

[Awayonmyboat]

Hopefully the OP doesn't have a problem, but if you have a minor, difficult to trace/fix leak you can add a sealant to the system. Toolstation and Screwfix sell suitable products for a few pounds that are designed for central heating systems.

[blackrose]

The Webasto installation instructions actually state not to chuck sealants or other additives to the system. 

 

Additives 
Please do not add any additives to the water cooling circuit. The only things that are permitted inside the heaters hot water circuit are : Water and Glycol. Do not add any additives for instance 'leak cures' or other 'plumbing fixes in a bottle'. It’s a pointless exercise fixing symptoms, fix the problem. If you have a leak then you need to fix the leak! 
 

[Midnight]

I'm pleased the OP has solved the problem. When any of these diesel central heating units won't start without running the engine it's invariable down to voltage drop. Earlier this year I replaced my old Mikuni MX60 with a Thermo Top C. Very quiet and heats the boat just as well. It did develop starting problems after 3 months out cruising so I checked the battery voltage 12.7v seemed sufficient so wondered about the unit itself. Then I spotted the voltage during the startup down to 10v. New batteries (ouch!) solved the problem.

[blackrose]

I've finally got my cheapo ebay reconditioned Thermotop C going today. 

 

All seems good. The first two rads from the boiler are very hot indeed but rad 3 is tepid & 4 is slightly warmer but not very hot. Everything has been bled.

 

I tried turning rads 1 & 2 down using the thermostatic radiatior valves to see if the heat would go through to rads 3 & 4 but that hasn't worked.

 

They are single panel 600mm x 400mm rads so about 2000 btu each (is that about 0.8kW?). I've also added a Kuranda blown air heater to the system and that gets hot, but that's the first item from the boiler. Rads 3  & 4 don't get hot whether the Kuranda is on or off. The calorifier is also hot but again that's close to the Webasto. 

 

Edit: actually rad 4 the last in the system is getting hot, but not rad 3.

 

 

 

Edited October 4, 2021 by blackrose

[Tonka]

42 minutes ago, blackrose said:

I've finally got my cheapo ebay reconditioned Thermotop C going today. 

 

All seems good. The first two rads from the boiler are very hot indeed but rad 3 is tepid & 4 is slightly warmer but not very hot. Everything has been bled.

 

I tried turning rads 1 & 2 down using the thermostatic radiatior valves to see if the heat would go through to rads 3 & 4 but that hasn't worked.

 

They are single panel 600mm x 400mm rads so about 2000 btu each (is that about 0.8kW?). I've also added a Kuranda blown air heater to the system and that gets hot, but that's the first item from the boiler. Rads 3  & 4 don't get hot whether the Kuranda is on or off. The calorifier is also hot but again that's close to the Webasto. 

 

Edit: actually rad 4 the last in the system is getting hot, but not rad 3.

 

 

 

Have you got any way of controlling the amount of flow through the calorifier 

[blackrose]

23 minutes ago, Tonka said:

Have you got any way of controlling the amount of flow through the calorifier 

 

I've got one gate valve on either the flow or return (can't work out which it is) to the calorifier. But I calculated that all the rads plus calorifier and pipework added up to about 3.8kW which is why I added the Kuranda heater (up to 1.6kW), to get it up to the 5.2kW of the Webasto. So I don't think I should need to reduce flow to anything unless I've miscalculated the pipework losses.

 

As rad 4 which is further away from the Webasto, is getting hotter than rad 3 what does that mean?

 

Having said that, I'm pretty happy that I've managed to install the Webasto myself and it's 90% working. ☺️

Edited October 4, 2021 by blackrose

[Tonka]

4 minutes ago, blackrose said:

 

I've got one gate valve on either the flow or return (can't work out which it is) to the calorifier. But I calculated that all the rads plus calorifier and pipework added up to about 3.8kW which is why I added the Kuranda heater (up to 1.6kW), to get it up to the 5.2kW of the Webasto. So I don't think I should need to reduce flow to anything unless I've miscalculated the pipework losses.

 

As rad 4 which is further away from the Webasto, is getting hotter than rad 3 what does that mean?

I know that on my system the calorifier valve is only open a very little and has been like this since the system was installed. I would certainly reduce the flow to it and see if that helps