• REMINDER - COVID-19

    Any content, information, or advice found on social media platforms and the wider Internet, including forums such as YBW, should NOT be acted upon unless checked against a reliable, authoritative source, and re-checked, particularly where personal health and liberty is at stake. Seek professional advice/confirmation before acting on such at all times.

    Users who are found to promulgate FAKE NEWS on the forum in regard to this issue, intentional or otherwise, may find their access terminated. It is your responsibility to provide references to bona fide sources.

    FAKE NEWS, in this regard, is that which is posited by organisations, media, etc., that is repeated on the forum, or used to support personal opinion/hypothesis posted by users - FAKE NEWS is not necessarily the personal opinion/hypothesis being posted in itself, any issues with such should be challenged respectfully.

Cummins Onan MDKP Service fault - Code 15

Asm

Member
Joined
23 Jul 2001
Messages
71
After running for 30 minutes or so, it fails and gives fault code 15 which in the manual is ‘Low AC Frequency’
It will immediately restart, then run for a similar period. There is definitely no excessive load!
As a first step I intend changing the fuel filter (although it is changed every year)
Has anyone else had this fault, if so, what was the fix? Thanks
 

ARE

Member
Joined
12 Jul 2010
Messages
185
Location
Norfolk
The under frequency is fault is directly sensed from the engine speed. I would check the fuel supply and the air inlet hose that runs from the air box on the front of the engine across the generator to the back corner, where it has been known to suck up to insulation.

I would also suggest you do measure the current draw first, just in case.
 

Asm

Member
Joined
23 Jul 2001
Messages
71
Thank you for the reply! Yes I’ll check those items, overcurrent is is definitely not an issue, it stopped with only the charger and one aircon unit on (usually runs three without issue)
 

Piers

Active member
Joined
2 Jun 2001
Messages
3,495
Location
Guernsey, Channel Islands
I'd check the frequency with no load, and see what happens as you bring load on. I had to adjust my Onan up to 51.5Hz so it kept going with high load.

Piers
 

Asm

Member
Joined
23 Jul 2001
Messages
71
Thanks Piers, I’ll follow Are’s tips first, then on my next visit here I’ll bring a frequency meter!
BTW we miss Toby dishing out the fudge, it’s a service we could do with on the islands!
 

Piers

Active member
Joined
2 Jun 2001
Messages
3,495
Location
Guernsey, Channel Islands
Toby dishing the fudge out? Now that really takes me back. He's now married to a gorgeous girl and they're expecting their first...And I'm trying to think who you are - can you pm me?
 

ARE

Member
Joined
12 Jul 2010
Messages
185
Location
Norfolk
I'd check the frequency with no load, and see what happens as you bring load on. I had to adjust my Onan up to 51.5Hz so it kept going with high load.

Piers
I assume that Asm unit is electronic governing, so this should not be an issue.

Asm,
Do you have a generator serial number please?
 

jimmy_the_builder

Well-known member
Joined
7 Sep 2005
Messages
8,751
Location
Sussex
I'd check the frequency with no load, and see what happens as you bring load on. I had to adjust my Onan up to 51.5Hz so it kept going with high load.

Piers
How did you adjust the frequency? I have a MDKBH and I suspect the frequency is slightly out - my induction hob sometimes complains unless I add some additional load to the generator.
 

Piers

Active member
Joined
2 Jun 2001
Messages
3,495
Location
Guernsey, Channel Islands
How did you adjust the frequency? I have a MDKBH and I suspect the frequency is slightly out - my induction hob sometimes complains unless I add some additional load to the generator.
Hi Jimmy,

I have two Onan gens. MDKAD & MDKAL. The one I had to adjust was the former, and the manual gives instructions on how to do it. There's a small lever (wire tied) just above the selector switch for 50 / 60Hz. It adjusts the genny's rpm. I had to set it to the max the induction hob would take before bombing out so as more and more load comes on and the rpm decreases slightly with an associated drop in Hz, the hob stayed working. Let me know if you need more info and I'll copy the manual for you albeit a different genny from yours.
 

jimmy_the_builder

Well-known member
Joined
7 Sep 2005
Messages
8,751
Location
Sussex
Hi Jimmy,

I have two Onan gens. MDKAD & MDKAL. The one I had to adjust was the former, and the manual gives instructions on how to do it. There's a small lever (wire tied) just above the selector switch for 50 / 60Hz. It adjusts the genny's rpm. I had to set it to the max the induction hob would take before bombing out so as more and more load comes on and the rpm decreases slightly with an associated drop in Hz, the hob stayed working. Let me know if you need more info and I'll copy the manual for you albeit a different genny from yours.
That's interesting, thanks Piers. My manual doesn't talk about this sort of adjustment at all. Perhaps the method is different on my generator. Thanks for the offer of the manual copy - but let's wait and see if (hopefully) ARE has any advice to offer on this adjustment first (might be completely different).
 

Piers

Active member
Joined
2 Jun 2001
Messages
3,495
Location
Guernsey, Channel Islands
That's interesting, thanks Piers. My manual doesn't talk about this sort of adjustment at all. Perhaps the method is different on my generator. Thanks for the offer of the manual copy - but let's wait and see if (hopefully) ARE has any advice to offer on this adjustment first (might be completely different).
Just checked and the detail is in the engine manual, not the ops manual.
 

jimmy_the_builder

Well-known member
Joined
7 Sep 2005
Messages
8,751
Location
Sussex
Just checked and the detail is in the engine manual, not the ops manual.
Aha - that makes more sense. In that case - can I change my mind and say 'yes please' to copy of the relevant section from your manual? I'll pm you my email address - thanks.
 

ARE

Member
Joined
12 Jul 2010
Messages
185
Location
Norfolk
Just checked and the detail is in the engine manual, not the ops manual.
Sometime around 2003 Onan swapped from mechanical governed Kubota engines (MDKA#series) to electronically governed Kubota engines (MDKB# series).

Piers generators are MDKA series with relay based control system, avr and mechanical governing. Jimmy’s unit is a MDKB series with a PCB controlling start/stop, diagnostics, avr and electronic governing.

With electronic governing there is no way to speed up or slowdown the engine adjusting the frequency. The problem with induction hob is not related to the frequency, the problem is related to the wave form produced by the brushed ac alternator on your 4MDKBH, you don’t have the same issues on a brushless ac alternators.

Regards Anthony
 

jimmy_the_builder

Well-known member
Joined
7 Sep 2005
Messages
8,751
Location
Sussex
Sometime around 2003 Onan swapped from mechanical governed Kubota engines (MDKA#series) to electronically governed Kubota engines (MDKB# series).

Piers generators are MDKA series with relay based control system, avr and mechanical governing. Jimmy’s unit is a MDKB series with a PCB controlling start/stop, diagnostics, avr and electronic governing.

With electronic governing there is no way to speed up or slowdown the engine adjusting the frequency. The problem with induction hob is not related to the frequency, the problem is related to the wave form produced by the brushed ac alternator on your 4MDKBH, you don’t have the same issues on a brushless ac alternators.

Regards Anthony
Hi Anthony, thanks for this. That's a shame though. Why is it that the induction hob works when the generator is slightly loaded (it's a 4kw generator and if I load it by say 25%, the hob seems to behave itself)?
 

ARE

Member
Joined
12 Jul 2010
Messages
185
Location
Norfolk
Hi Anthony, thanks for this. That's a shame though. Why is it that the induction hob works when the generator is slightly loaded (it's a 4kw generator and if I load it by say 25%, the hob seems to behave itself)?
Hi Jimmy, it’s because adding a small load smooths the waveform provduced by the ac alternator.

Regards Anthony
 

Asm

Member
Joined
23 Jul 2001
Messages
71
The serial no is J130585030 290 hours. No sign of insulation blocking the intake. I changed both filters, the Separ pre filter contained a small quantity of fragmented paper, I haven’t a clue how it got there. Sod’s law stepped in on the Separ filter change, the weld was broken on one of the winged bolts, so the ‘wing’ just turned, I had to remove the whole filter to enable the bolt to be extracted, luckily I had a suitable bolt to act as a temporary replacement. I ran the generator under high load for 1 1/2 hours. Thanks Anthony, any further comments?
 

ARE

Member
Joined
12 Jul 2010
Messages
185
Location
Norfolk
The serial no is J130585030 290 hours. No sign of insulation blocking the intake. I changed both filters, the Separ pre filter contained a small quantity of fragmented paper, I haven’t a clue how it got there. Sod’s law stepped in on the Separ filter change, the weld was broken on one of the winged bolts, so the ‘wing’ just turned, I had to remove the whole filter to enable the bolt to be extracted, luckily I had a suitable bolt to act as a temporary replacement. I ran the generator under high load for 1 1/2 hours. Thanks Anthony, any further comments?
So you have found the problem, I guess?
 
Top