Mikuni Diesel boiler

[Theo]

Theodora is fitted with a Mikuni Diesel boiler and I am not sure what is the matter with it.

 

1. It did not work at all until we charged the batteries to a reasonable voltage. I did not find that very surprising.

2. It then worked reasonably reliably for a whole two weekends and a Saturday morning. It does not seem to have any sort of thermostatic control on it so the domestic water got very hot. One thing that I noticed is that the spark igniter seems to work continuously as there is a ticking noise from it all the time.

3. Yesterday morning it work fine for a while. I then switched it off for a couple of hours and when I switched it on again there was nothing. Not even the green light on the switch. As we were leaving the boat I switched it again to see if anything would happen. The green light came on but I did not have time to let it go through the start cycle so I switched it off again, turned off the battery master switches and went home. This morning nothing again. Not even the green light. One further thing. It makes a high pitched peeping noise on verious random occasions. At least, I think it is the MIkuni and nothing else!

 

Any ideas anyone?

 

Nick

[DaveR]

On the control panel is there a flashing red light ? The number of flashes tell you what's wrong. If you don't have a list of the flash = meaning list i can copy you.

[charles123]

Theodora is fitted with a Mikuni Diesel boiler and I am not sure what is the matter with it.

 

1. It did not work at all until we charged the batteries to a reasonable voltage. I did not find that very surprising.

2. It then worked reasonably reliably for a whole two weekends and a Saturday morning. It does not seem to have any sort of thermostatic control on it so the domestic water got very hot. One thing that I noticed is that the spark igniter seems to work continuously as there is a ticking noise from it all the time.

3. Yesterday morning it work fine for a while. I then switched it off for a couple of hours and when I switched it on again there was nothing. Not even the green light on the switch. As we were leaving the boat I switched it again to see if anything would happen. The green light came on but I did not have time to let it go through the start cycle so I switched it off again, turned off the battery master switches and went home. This morning nothing again. Not even the green light. One further thing. It makes a high pitched peeping noise on verious random occasions. At least, I think it is the MIkuni and nothing else!

 

Any ideas anyone?

 

Nick

 

 

Nick

 

They have two power settings (you cant alter these) once the unit reaches a certain temp, sorry dont know what it is for sure but I think its 68 degrees, the unit cycles down to the lower heat setting. It is usual that the domestic water gets very hot. The ticking noise is not a spark ignitor its the fuel pump, quite normal. The unit should be powered independantly of the master switches, this is to prevent you switching off the power to it when its operating. When you switch it off it goes into a cooling cycle before it switches itself off, if you were able to switch it off at the master switches you would cut the power to the heater and it would not run the cooling cycle thus you could damage the unit. It should therefore be wired direct from the battery via an in line fuse. The unit uses 55 watts on high power so is power hungry. Hopefuly your problem is that the batters are too low to run it, as it wont run if the voltage is too low. Best thing is charge the batteries and switch it on with the engine runing. If it still does not work then its something else. As has already been suggested the frequency of flashes on the unit if it has gone into faultmode will give you an indication of whatthe problem is. Check out the mikuni web site for more

 

Charles

[Tommo]

Theodora is fitted with a Mikuni Diesel boiler and I am not sure what is the matter with it.

 

1. It did not work at all until we charged the batteries to a reasonable voltage. I did not find that very surprising.

2. It then worked reasonably reliably for a whole two weekends and a Saturday morning. It does not seem to have any sort of thermostatic control on it so the domestic water got very hot. One thing that I noticed is that the spark igniter seems to work continuously as there is a ticking noise from it all the time.

3. Yesterday morning it work fine for a while. I then switched it off for a couple of hours and when I switched it on again there was nothing. Not even the green light on the switch. As we were leaving the boat I switched it again to see if anything would happen. The green light came on but I did not have time to let it go through the start cycle so I switched it off again, turned off the battery master switches and went home. This morning nothing again. Not even the green light. One further thing. It makes a high pitched peeping noise on verious random occasions. At least, I think it is the MIkuni and nothing else!

 

Any ideas anyone?

 

Nick

If you have no light on the ON/OFF switch and the batteries have some charge in them it is quite likely you have blown one of the fuses, which are situated, beneath the control box.

They are blade type car fuses and I think it will be the 20amp one (MX40).

Replace this then without firing up the heater count the number of flashes on the control box. Seven is the usual and shows a problem with the glow plug. If so remove the plug and you will see is either completely carboned up or the element is broken. If only carboned up you may be able to carefully clean with a wire brush, don’t try and straighten the element as they are very brittle and will break. If you are able to clean the plug and get it going look upon it as a temporary measure and get a new plug ASAP. If fitting a new plug it is vital you remove the glow plug boss assembly and clean out the gauze and the swirl holes or your new plug will be very short lived Make sure you get a new gasket for the glow plug boss at the same time.

 

The above comes from living with a Mikuni MX40 for 3 years. I think you need to look on the plug as a consumable item and replace annually.

I have recently completely stripped mine down and serviced it with no trouble

 

As has been previously said the ticking noise is the fuel pump and is normal.

 

You can order parts direct from mikuniheating.com

Ian

[Theo]

As far as I know there are no indicator lights of any sort except the green one on the main switch. I could do with an instuction book and service manual, I think! I will trawl the web and see what I can find. At the moment I don't even know which model I have.

 

Thansk everyone for the useful info.

 

Nick

[Theo]

As far as I know there are no indicator lights of any sort except the green one on the main switch. I could do with an instuction book and service manual, I think! I will trawl the web and see what I can find. At the moment I don't even know which model I have.

 

Thansk everyone for the useful info.

 

Nick

 

Just realised that I never told the kind people who gave advice what the outcome was.

 

The problem was the power feed from fuse board. Just a loose connection and nothing to do with the Mikuni at all.

 

All the best

 

Nick