Mikuni heater problems

[BlueSkyNick]

Any experts around here? SWMBO is refusing to go off on the boat for a few days until I have sorted this out.

The heater worked OK in the autumn but having tried to use it recently it failed to run properly. Basically it starts and gets hot for about 2 minutes then cuts out. I switched it on again, same thing happened but then it stopped completely. I found that the 25Amp fuse had blown. I replaced it and the very same thing happened.

It sounds like it is trying to run but speeds up, and slows down rather erratically. I am getting some heat out of the vents, and blue exhaust fumes.

Having looked at the trouble shooting flow diagram and parts list on the Mikuni website, I have removed the heater from the bulkhead and taken the cover off.

I have removed the glow plug and what I now know as the Overheat sensor and flame sensors, but not yet disconnected their wiring.

The pictures below show these.

I don’t know if the plug is good, bad or indifferent but having got as far as I have, I plan to replace it anyway.

For the two sensors, I don’t know if I need to replace them or just clean up the surfaces and refit them. If I do this, do they need some form of cement to ensure proper heat conductivity?

All help gratefully received, for the sake of marital relations !!

 

[David2452]

Blowing the main fuse on a Mikuni is indicative of air motor or glow plug issues, from your symptoms it could easily be the air motor as a plug would give an instant blow on switching on, would you like a manual? BTW what model is it.

 

[BlueSkyNick]

Brilliant, thanks David.

I would love a manual, there isnt one on the Mikuni Heating website.

It is an MY30.

 

[David2452]

OK, PM me your email address and I will send you a PDF copy tonight. BTW, I do use a bit of heat sink compound if I can't get a really good clean contact for whatever reason, otherwise not needed and it is rare that I do so.

 

[sailorman]

Glo plug £19.75 delivered

Fleabay Item number
280820164996

 

[pcatterall]

Most of those componants have a resistance value or range which you will hopefully find in your 'new' manual Mostly when I test them they are either shorted or open circuit. Otherwise I rarely see one with a 'wrong' value.

 

[David2452]

Most of those componants have a resistance value or range which you will hopefully find in your 'new' manual Mostly when I test them they are either shorted or open circuit. Otherwise I rarely see one with a 'wrong' value.

Strange, I find just the opposite, especially when tested at varying temperatures, must be an ol Ebo thing.