Mikuni MX40 Control box (ECU)

[Ex-Member]

The Makuni heater failed on our last day over Christmas/New Year and coincidently we had it booked in for an annual service today by Justin Greene. He said that normally a service rectifies any faults but he rang to say that the control box indicator kept showing there was a problem with the glow plug, even though he had replaced it. I know these heaters can be troublesome and they are like marmite but I also read, on here I think, about the control boxes not always showing the correct fault. Before I rush out and buy a new one (approx £300) does any one have any experience of this kind of fault or can advise? If I have to buy one is it something that can be fitted easily i.e. DIY?

Edited January 16, 2017 by Numpty

[adrianh]

Yes, I used to see the same fault when the control box had got damp ( in the engine bay under boards) and had to dry it out at home.

Also the lead to the glow plug connection at the box needed to be cleaned - this is an funny plug type.

 

Fitting a replacement is easy once you work out how to release the plugs, I still have the old one on the boat so could look if you want next week

 

The control box checks for the glow plug to have a suitable resistance ( also the fan motor) before allowing combustion to start.

Have you checked the glow plug as heavy carbon deposits give the wrong resistance an will show this fault. Or try a replacement.

 

I also had a similar mode of failure when the supply to the control box developed a bad connection at the 20/30 amp supply fuse in the lead just before thebox

 

 

In the end my control gave up and I purchased a used one for about £80 from a local repairer, so far I have not seen the same fault.

 

You would be better to put £300 towards a webasto - spares for a Mikuni are now rare and expensive

[Ex-Member]

Yes, I used to see the same fault when the control box had got damp ( in the engine bay under boards) and had to dry it out at home.

Also the lead to the glow plug connection at the box needed to be cleaned - this is an funny plug type.

 

Fitting a replacement is easy once you work out how to release the plugs, I still have the old one on the boat so could look if you want next week

 

The control box checks for the glow plug to have a suitable resistance ( also the fan motor) before allowing combustion to start.

Have you checked the glow plug as heavy carbon deposits give the wrong resistance an will show this fault. Or try a replacement.

 

I also had a similar mode of failure when the supply to the control box developed a bad connection at the 20/30 amp supply fuse in the lead just before thebox

 

 

In the end my control gave up and I purchased a used one for about £80 from a local repairer, so far I have not seen the same fault.

 

You would be better to put £300 towards a webasto - spares for a Mikuni are now rare and expensive

Thanks for your reply but yes the engineer, Justin, has tried all that (apart from the damp bit) He went back to the boat yesterday as he was servicing another boat's mukuni, he swapped the control boxes and theirs worked on our boat but ours did not on the other but showed the same fault so Justin emailed this morning to say he believes it is the control box that needs replacing. I agree with you, I am loath to spend £300 for a new box, I don't suppose you have a contact for the used one you bought?

[NMEA]

Has the fault been cleared down? sometimes the control box retains the fault and will not start and keep reporting the fault. In those cases a simple reset of the control box is all that is required, just remove the main fuse for a few seconds and re insert.

[WotEver]

Has the fault been cleared down? sometimes the control box retains the fault and will not start and keep reporting the fault. In those cases a simple reset of the control box is all that is required, just remove the main fuse for a few seconds and re insert.

Surely trying the box in another boat would have achieved that?

[NMEA]

Surely trying the box in another boat would have achieved that?

Missed that bit, still worth checking out the Control box though as unlike more modern heaters they are simple analogue electrics.

[WotEver]

Missed that bit, still worth checking out the Control box though as unlike more modern heaters they are simple analogue electrics.

Which makes one wonder at the £300 cost...

[Ex-Member]

Which makes one wonder at the £300 cost...

Well I spoke with Mukuni this week & they said they would sell me a used one for £100 + vat & postage. Then I spoke with Ed at FCMarine and he could sell me one for £80 with 12 mth warranty so at the moment I think that is the option we will take. It will give us time to decide what to do in the long run. Other than the control box, which I am sure Justin has tried everything to test it, he said the unit was in fine fettle even though it hadn't been serviced for 2 yrs it didn't even need the glo plug changing. So I reakon £80 is worth a go.

[NMEA]

Got to be worth £80, even if you only get a year or two out of it whilst you plan and research a replacement. Could even go on for years, they are inefficient and agricultural bits of kit but very robust if given clean diesel.

[Ex-Member]

Got to be worth £80, even if you only get a year or two out of it whilst you plan and research a replacement. Could even go on for years, they are inefficient and agricultural bits of kit but very robust if given clean diesel.

 

Well that's what we thought. Justin, the service engineer, said that the unit is in excellent condition and looks like it has hardly been used which was confirmed by Ed at fcmarine who knows the boat because coincidently he went to see it about two years ago. The previous owners were having problems starting it and he replaced the wires for thicker ones as he felt that was the problem. Prior to that he said the owners hadn't used it much. It was all a bit weird because ED advertises on fleabay and his listing shows a positive comment from the previous owners.(which I only found out afterwards) I don't think we have anything to lose at £80 with a 12mth warranty especially as, if it does go again, we will probably go for a Webasto and Ed said he would knock the £80 off the price of supplying/fitting a new one. I hope you are following this as there will be questions later.......

[Ex-Member]

Closure for now

The makuni is up and running again with a big thank you to Ed Shires at FC Marine (07922 163 072 ed@fc-marine.co.uk).

 As well as the ECU their was an air lock in the fuel supply line which he cleared by disconnecting the fuel line & running the system a couple of times,,,then off she went; nice guy would defo use/recommend him!

 

[PeterG]

I have a Mikuni which has never really worked and am currently saving up my pennies to replace it with something else.  Considering it has not been usable for probably 6 years, it is not a high priority to replace, as I use a stove for heating and a small immersion heater when in the mooring.  If I do remove or replace it then I will offer any or all of it on here to whoever can make use of it.