Onan 17.5 kva generator shut down PCB again.

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aquatom

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Hello.

Has anyone else had the same problem of faulty electronic control units (ECU's or PCB's).

I have replaced them on many different boats now and have had two fail again after only a few hours running. Onan say it must be user error but one has failed whilst I was on the boat with the generator running and the air con on, then it just stopped and had no sign of life.

I would be very interested to hear from anyone else who have had this problem.

Tom
 
aquatom said:
Hello.

Has anyone else had the same problem of faulty electronic control units (ECU's or PCB's).

I have replaced them on many different boats now and have had two fail again after only a few hours running. Onan say it must be user error but one has failed whilst I was on the boat with the generator running and the air con on, then it just stopped and had no sign of life.

I would be very interested to hear from anyone else who have had this problem.

Tom
Click to expand...

I've had prob but not as bad as you. Mine failed jan this year. 1650hrs, 5yrs old, 17.5kw model. Needed new pcb then ran fine. I sold boat soon after

New boat also has the 17.dkw, now 8months use and 310hrs. All fine so far!
 
Suggest you give Chris Willey @ Contact Marine a call or Email

contactmarine@ntlworld.com

02392 797112

07889 431096

Have used him for years to service and repair the various Onan Gensets I have had. He knows everything about Onan and was recommended by them.

-Andrew

P.S I have a 18 month old Onan 17.5 - 130 Hours - faultless - so far!
 
We have Onan 13.5 kw, 5 yrs old, no idea how many hours as i've never looked, but I know it has done hundreds of hours this summer alone, and no probs so far.
 
Onan Generator

Hi Tom,

Found your post by accident, I must thank Andrew for his kind recommend!
I need to know the model number, serial number and hours before giving advice. How many control PCBs have failed? Also boats construction, GRP, Steel, Wood?

Chris
Contact Marine Ltd
(0)7889 431096
 
contactmarine said:
Hi Tom,

Found your post by accident, I must thank Andrew for his kind recommend!
I need to know the model number, serial number and hours before giving advice. How many control PCBs have failed? Also boats construction, GRP, Steel, Wood?

Chris
Contact Marine Ltd
(0)7889 431096
Click to expand...

FWIW, mine that failed was an MDKBE 17.5kw, Kubota 4 cyl engine, pcb failed at 1650hrs, 5yrs old. Ran at 230v 50Hz speed (1500rpm?). Boat was GRP - fairline Sq58 2004 model owned from new. I don't have serial #

While you're on, is the MDKBT an ok model (22.5kw, 50hz, GRP boat)? Anything special to watch out for? Does it eat water pump vanes like some of them? Thanks
 
To date I have personally changed 6 boards but know of many others. They all have been Fairlines mainly Phantom 50s but one Squadron 58.

Onan UK have been very helpfull and have sent two replacements (free of charge) for the ones that failed so soon after being fitted.

It still seems a mystery as to what causes it.

Any ideas?
 
Onan Controllers

There are two possible issues that I know about, you need to check the shore / generator changeover contactor, Fairline used to install a single contactor to do this job, unfortunately it was AC1 rated (resistive loads), when it should have been (in my opinion) AC4 rated (inductive loads).

When switching over from generator to shore support, especially if ACU's are running, it was not unusual to draw an arc across both sets of contacts - effectively paralleling the generator and shore supply together. This fault has been responsible for the demise of many control PCBs!

After a long meeting between myself and Peters Boatyard, (then the UK Fairline agent) they changed to a two contactor changeover system with AC4 rating.

One of the warning signs that this may be happening is frequent tripping of the shoreside RCCD (Earth fault breaker), when switching from generator to shore support, or visa versa.

The control PCB fitted to your set is generally a very good unit, we had a few fail after extensive use, these faliure's were caused by vibration fatigue of one of the components mounted on the PCB. Onan changed the support structure of this component and faliures are now extremely rare.

I would strongly recommend getting a competent Marine Electrician to check the type of changeover contactor fitted to your vessel.

As a footnote, Onan do a conversion harness kit that allows the use of the latest controller - which incidently is cheaper, however it won't work if you have remote instrumentation.

The 22.5kW MDKBT has the latest controller, I am not aware of any issues with impellor blades shedding, I would however recommend changing the raw water pump every 2500 hrs. Two modes of faliure - pump wont prime on start up, even with new impellor! Very rare but has happened faliure allowing saltwater into oil - Nasty!!

If this does not provide the answer, or it is not clear what I mean the please get back to me.

Chris
Contact Marine Ltd
 
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That makes a bit of sense. I will check what contactor set up these boats have. We were supplied with uprated pcbs and a modified adaptor loom.

Would this contactor problem cause the pcb to fail whilst the engine was running and no shore power connected?

Tom
 
contactmarine said:
The 22.5kW MDKBT has the latest controller, I am not aware of any issues with impellor blades shedding, I would however recommend changing the raw water pump every 2500 hrs.
Click to expand...

Thank you Chris. All makes good sense. When you say change pump at 2500, you mean the whole pump body, right? The rubber impeller would be changed every 200 or so (or whatever the manual says)

Also where/who would you recommend in the UK as an Onan parts supplier? I like to have a biggish stock becuase you never know when you're gonna use the genset a lot then suddnenly need to do a quick service. I'd like to get 2 years worth of service items into stock for 2 x MDKBT. Do you supply?
 
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Onan Controllers

If you have the adapter cableform harness then you have the latest controller installed, we have had no issues with this controller at all, so if you are getting faliures then it is almost certain that an external problem is causing it.

The contactor issue can only occur when shore supply is available and plugged in.

Is you generator negative ground or isolated ground? If you don't know then I can find out from the serial number, if you can let me know it.

The entire Raw water pump should be changed at 2500 hrs. (This is not an Onan recommendation).

I would be delighted to supply spares for your generators

Chris
Contact Marine Ltd
 
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I have onan MKDBsummink 3500 hrs ish not at boat at the mo and had shutty down problems. Cleaning out the contactors with the squirty cleaner sorted it. Lots of the hoses etc needed tightening. The pencil anode lasts 18months, small pump vanes just get mashed cos they're small and crunchable i think and get swapped at 6months ish.

Major prob for me was that the giant relays blew so generator all fine - just the relays wdn't let any power thru and the things proper melted so not screwdriver-jammable...
 
Hi TCM,

I am assuming that you have a MDKUB which is is a 3000RPM set. However the MDKUB doesnt have an anode so if its not, please send me the correct model number.

Regardless using a screwdriver to push contactors in is definately a no! This could easily cost you several thousands of pounds or euros of damage to your generator!!

If the contactors have failed, check their rating!! Check the max output in amps on your generator rating plate and then check carefully what the AC4 rating is on the contactor. If its not man enough get it upgraded!!

This MDKUB Genset does not have have a 'controller PCB' as such and is not related to the sets that I have previously been dealing with. However it may still have the changeover problem that I discussed in previouse threads!

Is your boat a Fairline? If so what years?

Because of the high speed nature of the MDKUB Genset, Onan have set service intervals at 150 Hrs so impeller faliure is much more common as the pump is running at twice the speed of the ' normal 1500RPM' Onan gensets. Frequent impellor failures can also be caused by obstructions in the raw water circuit, this can be on the suction side of the pump or the pressurised side, likely candidates are heat exchanger input side ( broken impellor vanes) and sometimes the exhaust injection elbow..

I am happy to answer questions, but due to the fact we are mobile and travel the UK and EU, it is possible that I may not respond immediatly to a question.

Chris
Contact Marine Ltd
 
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gosh this is rather wonderful. I dunno, it has mkdb and perhaps some other letters- nice gen, iffy model numbering. Only 7+kva and not a fairline. Thanks for the concern.

However, i'm afraid that must reserve my rights to personally cause thousands of pounds of damage to complex items of marine equipment due to hardly looking at manuals and variously hm prodding things with screwdrivers etc. In fact, I often think that this may be one of the attractions of boating, no?
 
Common Boat Problem

I encountered a similar problem before. I was close to purchasing a new generator until I was recommended to a shop in Alberta that offers generator parts so I've managed to save myself a chunk of cash. That company now provides all my heavy equipment as they sell brand new and used equipment and parts.
 
contactmarine said:
If you have the adapter cableform harness then you have the latest controller installed, we have had no issues with this controller at all, so if you are getting faliures then it is almost certain that an external problem is causing it.

The contactor issue can only occur when shore supply is available and plugged in.

Is you generator negative ground or isolated ground? If you don't know then I can find out from the serial number, if you can let me know it.

The entire Raw water pump should be changed at 2500 hrs. (This is not an Onan recommendation).

I would be delighted to supply spares for your generators

Chris
Contact Marine Ltd
Click to expand...

Chris,

Changing raw water pump out at 2,500 hours is real sound advice. Having completed a design review of Sherwood pumps fitted as OE equipment on CAT, Cummins and Deere propulsion engines as well a as whole rake of generator engines including Onan I discovered that the pump body material analysis showed a material be a real crude alloy, certainly not to the same spec as the Admiralty bronze used at one time by Jabsco. Seals were designed by a complete drawing office numpty.

Engine overheating at anything over 3,000 hours invariably means that Sherwood pump body in on the way out..Owner says 'but I fit new impeller ever year'
 
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