Mikuni MY30 no electrical feed at control

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Fenders

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I have recently bought a yacht which has a Mikuni MY30 heater. I am lead to believe it is approx. 10 years old.
When the surveyor tried to test the heater the leds on the control failed to illuminate, leading him to believe that there must be an inline fuse somewhere.
He briefly looked around for anything obvious but no joy.
When the broker was advised he called the vendor to be told that "it was working the last time we used it last year".
The vendor didn't have a manual either.

I have looked at the Mikuni website but the fault flow chart doesn't help in this instance.
So, can anyone advise me as to where I should begin to look for a fuse.
I thought I should ask here first before I start stripping down the boat.

Thanks in advance
 
I have a 20 year old MY30 - good news, it still works, so they're obviously built to last!

There is no fuse as standard, so if there is one it would be added by the installer (and there should be one somewhere!!)

It sounds like a power supply fault, as if the heater has power but is in a fault mode the lower led on the controller would be illuminated red.

It could be a simple wiring issue between the heater/ecu/controller so once you've established a healthy power supply start looking at the plugs/connections between the modules.
 
If you would like a manual with wiring diagrams just drop me a PM with your email address. The 12v MY30 has a single 30a fuse on the power supply, this should be close to the battery if correctly installed with the standard supplied loom, the power for the control unit is supplied from the ECU, pretty easy to trace back using the wiring schematic.
 
I have found a 30 amp fuse close to the control box next to the heater unit. This is ok.
I then followed the power cables back to its source. I was surprised to see it connected to the boats main power busbar and it has a 30 amp fuse as well. It was hidden behind the boats electrical panels. This fuse had blown.
I could find a 30 amp replacement but I did have a 20amp one which I fitted.
I turned on the heater and the green LED came on. Great I thought. Got power at last.
I then called for heat on the thermostat. The red LED came on. I guess the system was going through a warm up period. About 90 secs later the new fuse blew.
Could this be a glow plug problem or something more serious?
Should I call an engineer to investigate and if so any recommendations?

Thanks

Fenders
 
If it's designed for a 30a fuse, that'll be why the 20a blew. Whilst I don't have a Mikuni heater, I have a Wallas diesel cooker, and during start up of either hob or oven, you have glow plug, fuel pump and fan running... on the cooker that's 8a for the glow plug and a couple for the others, and the oven and hob are individually protected by 15a fuses. Simple maths means if yours requires 30a fuse, then the glow plug is at least half that, and the fans and pump would easily push it over 20a
 
Generally speaking the fact that it blew the original 30a fuse is a strong indicator of a glowplug issue, they are old technology resistive coils and do short out regularly. Fortunately they are really cheap and worth keeping a spare aboard. Very easy to change but take careful note of the positioning of the insulating spacers as you remove the leads from the plug. Get a few new 30a fuses and a couple of plugs and my money is on an easy fix, it's all I usually have to do when called out to blown fuses on Mikunis of all flavours. Even a good plug will draw > 18a during initial heat so the 20a fuse would blow anyway, it's the 30a fuse blowing in the first place that is the clue to diagnosis.
By the way the way it is connected to the main power bus with an adjacent fuse is correct, assuming the bus is not controlled by a breaker switch, either there or direct to the house bank. Main thing is no possibility of accidental crash stop without cooling cycle.
 
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When I am on the boat in a few days time I will check the glow plug.
Thanks for all your most helpful advise.
I will report my findings later as it may be of interest to others.

Fenders
 
I have returned from the boat.
After spending ages emptying my cockpit locker again to reach the heater, I managed to extract the glow plug. It was a bit sooty so I clean it up very gently and refitted it. I then inserted a new 30 amp fuse at the busbar and switched on the heater. To my amazement I had lights at the thermostat and the sound of a blower in the cockpit. About 90 secs later a large plume of smoke was emitted from the transom. This continued for maybe 5 mins gradually decreasing in intensity. Down below I checked the vents and sure enough warm air was blowing through. I let the system run for 10 mins just to burn off any coking and to give the heater a chance to settle down. I then turned it off. The shut down process took about 10 mins.
About 3 hrs later I tried it again with success.

I shall continue to use the old plug and I have a new one on order as a spare.

So, many thanks to David and Gladys for all your advise.

SWMBO is very happy now!!

Fenders
 
Fenders said:
I have returned from the boat.
After spending ages emptying my cockpit locker again to reach the heater, I managed to extract the glow plug. It was a bit sooty so I clean it up very gently and refitted it. I then inserted a new 30 amp fuse at the busbar and switched on the heater. To my amazement I had lights at the thermostat and the sound of a blower in the cockpit. About 90 secs later a large plume of smoke was emitted from the transom. This continued for maybe 5 mins gradually decreasing in intensity. Down below I checked the vents and sure enough warm air was blowing through. I let the system run for 10 mins just to burn off any coking and to give the heater a chance to settle down. I then turned it off. The shut down process took about 10 mins.
About 3 hrs later I tried it again with success.

I shall continue to use the old plug and I have a new one on order as a spare.

So, many thanks to David and Gladys for all your advise.

SWMBO is very happy now!!

Fenders
Click to expand...
An MY30 is essential kit, in June :disgust:
 
Excellent news, if it's working then continue with the current plug but make sure you have a spare to hand along with some fuses. Don't forget to run it for half an hour once a month even through the summer.

Fenders said:
I have returned from the boat.
After spending ages emptying my cockpit locker again to reach the heater, I managed to extract the glow plug. It was a bit sooty so I clean it up very gently and refitted it. I then inserted a new 30 amp fuse at the busbar and switched on the heater. To my amazement I had lights at the thermostat and the sound of a blower in the cockpit. About 90 secs later a large plume of smoke was emitted from the transom. This continued for maybe 5 mins gradually decreasing in intensity. Down below I checked the vents and sure enough warm air was blowing through. I let the system run for 10 mins just to burn off any coking and to give the heater a chance to settle down. I then turned it off. The shut down process took about 10 mins.
About 3 hrs later I tried it again with success.

I shall continue to use the old plug and I have a new one on order as a spare.

So, many thanks to David and Gladys for all your advise.

SWMBO is very happy now!!

Fenders
Click to expand...
 
David2452 said:
Excellent news, if it's working then continue with the current plug but make sure you have a spare to hand along with some fuses. Don't forget to run it for half an hour once a month even through the summer.
Click to expand...

Why? Genuine question as I have one of these and am rather ignorant as to it's mysteries having only had it (and the boat it came with) for less than a year.
 
Reasoning is: Keeps fresh fuel in the lines, helps prevent sticky bearings and sticky dosing pump and equally importantly might show up faults that can be sorted at leisure before you have to use it in anger and have to freeze for a couple of trips whilst it is fixed.

Elecglitch said:
Why? Genuine question as I have one of these and am rather ignorant as to it's mysteries having only had it (and the boat it came with) for less than a year.
Click to expand...
 
David2452 said:
Reasoning is: Keeps fresh fuel in the lines, helps prevent sticky bearings and sticky dosing pump and equally importantly might show up faults that can be sorted at leisure before you have to use it in anger and have to freeze for a couple of trips whilst it is fixed.
Click to expand...

Ack, thanks
 
Fenders said:
I have found a 30 amp fuse close to the control box next to the heater unit. This is ok.
I then followed the power cables back to its source. I was surprised to see it connected to the boats main power busbar and it has a 30 amp fuse as well. It was hidden behind the boats electrical panels. This fuse had blown.
I could find a 30 amp replacement but I did have a 20amp one which I fitted.
I turned on the heater and the green LED came on. Great I thought. Got power at last.
I then called for heat on the thermostat. The red LED came on. I guess the system was going through a warm up period. About 90 secs later the new fuse blew.
Could this be a glow plug problem or something more serious?
Should I call an engineer to investigate and if so any recommendations?


Thanks

Fenders
Click to expand...
Chat to MIkuni first. They are very helpful and do a repair and service package for the heater which is easy to remove. They are excellent heaters and very reliable - mine is now 20 years old and never fails to work. I habve both the operators and repair manuals if you pm me your email address.
 
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