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Generators In this forum we will try to answer any of your questions about the different model generators that can be found on Blue Bird coach's.

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  #1  
Old 04-06-2017
trystero trystero is offline
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Default 12.5 Kubota/Yanmar generator stops

****. I'm not too proud... I usually can figure stuff out if I beat my head on it long enough. But this has me stumped and before I spend big bucks I want to see if I can get some renewed direction from the experts. I've poured over REALLY good and informative posts here on site on figuring these things out but still no luck getting this thing back running. Anyway, here is my problem.

I have a '86 PT40. Arguably the finest motorcoach every made by man. The generator is Kohler/Yanmar 12.5. It has run reliably for years. 4 or 5 years ago I replaced the 230v cooling fan with modern 12v. It has worked since without issue. That is the only modification. The other day I started it (I try and start every 2-3 weeks regardless) and after running for a few seconds, shut itself off by de-energizing the fuel solenoid.

Battery condition is excellent.
Oil level good.
Coolant level good.
Engine starts almost instantly and strong which is typical until shut-down, 3-5 seconds.
I have unhooked engine sensors one at a time and same shut down.
I have pulled control box and checked for loose terminals.
I have cleaned and properly reattached grounding strap.
I replaced the (3) Bosch relays. The existing ones were metal cased and just appeared old.
I did not replace the high voltage relay which appeared to be in excellent condition.
I can force engine to run by hold back fuel cut-off solenoid. When I do this the generator IS producing power as indicted on the front dash high voltage gages. The rocker start switch light DOES NOT illuminate.
If I hold back the solenoid for longer than 30-45 seconds, the engine sputters a bit but continues running. I haven't keep running longer than that.

I hope there are some clues that might lead to a solution. Perhaps a diagnostic I have overlooked.
Any questions please ask and thanks in advance for any help or direction.

Robert
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1986 PT40
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Austin, Texas
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  #2  
Old 04-06-2017
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racin41bb racin41bb is offline
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Our '87 FC had a intermittently open wire in the harness. Generator is on a slide and flexing over time may have caused the open circuit. We rewired around the open wire. A subsequent problem involved several cannon connectors. I replaced most of the pins in the plugs & sockets and rewired the ones that connected directly to the control box.

I don't know if this will help since you are producing power by holding the fuel solenoid in the run position--our unit did not produce power either time we had generator issues.

Bill
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Bill & Rita Brinner in Roanoke, VA
"IRON HOUSE"
1987 FC-35SB ('87 factory demo)
Cat 3208ATAAC-300
12.5kw Kohler/Yanmar (w/slide)
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Steve Goodman 1970

"You never fail until you stop trying".
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Old 04-06-2017
BobsBus BobsBus is offline
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If the light in the start/stop switch does not come on, the engine safety system does not know the oil pressure came up, or thinks the coolant is over temp.

You may have to jump the senders instead of disconecting them to find the problem. Some systems use a loss of current to signal a fault, others use a closing switch to signal a problen.

The short run time is that the safety shut down system is overriden during cranking for a short time.

Just a few thoughts for you.

On my 1985 PT, I need to keep the start switch held down until the switch light comes on to keep the motor running. If I release the switch before the light comes on, the generator motor stops.
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1985 PT 40 BB
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Old 04-06-2017
K Ridley K Ridley is offline
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It sounds like the 11 pin ice cube relay is not working. When this relay receives 120 volts it closes contacts to turn on the switch lights and energize the hold in on the fuel solenoid. You should be able to start it without the cover on the control box and see if the relay is activating.
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1979 FC35 XV (Sold!)
1986 PT40 Amazing Grace (Full Timing It)
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Old 04-06-2017
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Blue Emu Blue Emu is offline
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Quote:
Originally Posted by K Ridley View Post
It sounds like the 11 pin ice cube relay is not working. When this relay receives 120 volts it closes contacts to turn on the switch lights and energize the hold in on the fuel solenoid. You should be able to start it without the cover on the control box and see if the relay is activating.
I had this exact problem on the desert of Quartzsite. The 120v relay sees power from the head, closes, and then all of the other safety relays are activated. Even when it LOOKS like it is closing properly, if one of the contacts is corroded or not making a good contact, the engine will stop.

I replaced my 120v relay (Thanks to a neighbor at Q who had one), and all is happy once again. Based on my experience, I would go there first.
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Old 04-07-2017
trystero trystero is offline
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Thank you all so much for the info. I'll get on it and report back!
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1986 PT40
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Austin, Texas
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Old 04-15-2017
trystero trystero is offline
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Kevin, you nailed it Buddy. It was the 11-pin "ice cube" relay. It looked to be in good order but replaced and now all good. Thanks to all for the feedback!
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1986 PT40
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