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General Discussion of preventative/corrective maintenance and other technical issues regarding your coach that are not covered in other Mechanic's Corner categories (ex. refrigerators, water heaters, and compressors).

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  #1  
Old 07-02-2019
Captain Fred Captain Fred is offline
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Default Onan generator

New to us 1987FC. Genset not running when we bought bus. Had overheated, we think, and shut down. Head gskt was replaced by P O and hasn't been run since as was popping back through intake. Found valves to be way out of adjustment and got engine running ok. Engine will start but not stay running unless hold shutdown solenoid back. Looked thru Onan Manual and find power to SP switch when cranking but no power after start.
Manual is pointing to bad DC control board. I did change the 2 Bosch relays in the control box as I had them on hand.
Also have no cooling fan when engine is running. Doesn't a no power generation situation shut down the engine ? Manual doesn't seem to address this.
Don't want to spend a lot of time and $ on getting engine right only to find the generator end is bad.
Am considering hot wiring the engine shut down solenoid in order to run tests on gen but Leary of damaging circuit board. ( if it isn't already toast )
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Old 07-02-2019
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gcyeaw gcyeaw is offline
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What model number is the Onan. I thought the fc 35's had the Kohler/Perkins set, but may have been an option.
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  #3  
Old 07-02-2019
Captain Fred Captain Fred is offline
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The 87 FC has the 8kw Onan with a d950 kubota mounted drivers side rear.
( I really wish it was mounted on a slide out. It will be if I need to do major work to it )
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Old 07-02-2019
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Quote:
Originally Posted by Captain Fred View Post
The 87 FC has the 8kw Onan with a d950 kubota mounted drivers side rear.
( I really wish it was mounted on a slide out. It will be if I need to do major work to it )
My brain saw 78 instead of 87.
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  #5  
Old 07-02-2019
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Steelwheels Steelwheels is offline
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Follow the flow charts in this book they are pretty decent.

https://www.wanderlodgeownersgroup.c...e%20Manual.pdf

I think you should be ok hot wiring it, someone else may know better. You can run a positive lead to the fuel solenoid that will hold it open and power the fuel pump.

My control box has been nothing but headaches for me, that d950 keeps rocking though.

Your cooling fan not running could be a bad capacitor it’s in the junction box near the blower, a few people have swapped out the blower for a regular auto radiator fan, I put one on mine. The generator didn’t seem to make enough dc power to keep it going with out draining the battery, I ended up putting a 120ac to 12dc power supply on it. Works pretty good I’ve have the power supply cut out a few times, I think a better quality one may be more reliable. No issues keeping it cool though.

The connectors in that amp connector are a common point of failure, I’ve changed most of mine to new connectors, you can disconnect the square molex connector that one is for the in coach functions the big round amp connector is the engine controls, I think the small one is to the voltage regulator generator ac control. Once you disconnect the square molex you can pull that large amp connector cable, bundle or wires around the back of box to the left of the control box and get the whole control box out to the front of the gen so it’s easier to troubleshoot. Get a bucket to sit on it will save your knees.

It’s really a simple design and I know a guy who runs a generator shop and said he’s seen one with 20,000 and likes them better than the quiet diesel.

Check your grounds are clean and good connections, look for broken wires on the spade connectors, I have had broken wires right at the place where the wire was crimped also a broken wire inside the amp connector.
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Last edited by Steelwheels; 07-02-2019 at 10:59 PM. Reason: Autocorrect spelling errors
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Old 07-03-2019
Captain Fred Captain Fred is offline
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Thanks Kiki,
Looks like that will be one of my 4th of July projects. Refinishing the r/f battery tray is on the list also. Some of the large AMP connector has already been jumped.
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Old 07-03-2019
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I agree with Kiki on the Onan DKD 8.0. They are great generators and will run a long time with maintenance. You can still buy the circuit boards for the controller as well. I believe John McGinnis moved his controller box so it wasn't mounted on the generator, where it vibrates a lot. Bill Pape I believe replaced the ever-broken red circuit breakers with maxi fuses.

My generator has an issue where it will not start sometimes and it's the shut off solenoid that is sticking. Once I pull it back it will start no problem. I also always start mine with zero load and let it run for a few minutes, then click the breakers on.

If you figure out a slide mechanism, please share!
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  #8  
Old 07-03-2019
Captain Fred Captain Fred is offline
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Ok, latest on the generator. Wife was home this afternoon so I had some help.
( had already found out that I can't be in 2 places at the same time )
I started the genset and held the shut down solenoid on while she checked the overhead gauges at the front of the bus.
Had 2 legs of 120 volts, turned on both air conditioners one at a time and got amperage readings on both legs. ( about 20 amps each ) & both ac's ran.
So genset is putting out, both legs.
Issues:
1. No cooling fan
2. Engine won't stay running on its own.
If I momentarily energize the connection on the shutdown solenoid that is also power to the fuel pump then the engine will stay running until I shut it down with the stop switch.
There are 2 Bosch relays in the dc control box.
1 is for glow plugs. What is the other for ?
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  #9  
Old 07-03-2019
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Quote:
Originally Posted by Captain Fred View Post
Engine will start but not stay running unless hold shutdown solenoid back. Looked thru Onan Manual and find power to SP switch when cranking but no power after start.
Manual is pointing to bad DC control board.
My new-to-me DKD had same symptom (starts/dies out). Hope yours is just a board, the DKD is real good equipment in my experience.

I found a burned trace on the bad board. It was really obvious, board scorched, foil trace distorted. I unwrapped the wire bundles outside the DC Controls box and found three wires with several inches of burned off insulation. See below how to deal with those plugs and wires.

A new board fixed the run problem. I bought a spare too. The aftermarket version is by Flight Systems, I think about $100 per board. That was 2012. I still run very reliably on the replacement board, have the spare in a box, these aftermarket boards are tough.

Some other problems a DKD might have:

The DC Control box has several pitfalls that can disable the gen and related instruments, only some of them are by design.

The gen remote start/stop and instruments didn't work. I investigated, in the upper dash, and found someone's lost screwdriver (uninsulated) laying along the gauge terminals! Count your tool before and after

When I took the connectors off the DC box, I found scorched pins. The discerning eye can see the problem pins as they have a little discoloration. Mine were a little bit speckled tan colored, like a spark plug electrode run a little lean.

Simple solution, by-pass the one or two burned pins with a jumper. Or do them wholesale--cut out the big round plug, one wire at a time, and butt-connector it. All the wires (12, I recall). Likewise I did the square plug (6-ish, CRS). If you do this, do yourself a favor and find a way to preserve the PIN number for each wire--you can write labels on paper and laminate them with Scotch tape wrapped around each wire. The diagrams (back of the DKD manual) trace each PIN number thru the DC system, so you'll want that pin/wire # connection info if you ever want to pull the gun out of the coach.

edit: SPELLCHECK!! You know I mean gen(erator) not gun(kulator)

The DC breakers are prone to failure, vibration apparently gets to them.

The Fault Breaker is a 3-wire GFI device, not a fuse. The DC Controls board signals it to trip when it picks up one of several possible engine sensor faults. Our DKD's don't have the full array of Onan sensor, just coolant and oil (no exhaust temp or engine speed sensor). Use an OEM 3-wire Fault breaker. It is manual-reset with a red stick that pops out. When it fails it can be tripped without popping up. I don't like OEM prices, there is probably a compatible, less pricey GFI breaker in the aftermarket, if a good parts man wants the challenge of finding it for us

DC Controls breaker seems to trip on just B+/ground issue, a loose wire in the DC Box or just a bad pin. I replaced with a Blue Sea manual-reset On/Off switch breaker. When my run solenoid linkage came apart, it couldn't couldn't pull back throttle to stop position, and I thought it was running away. Onan Run/Stop switch wouldn't work with broken mechanical linkage. So I like the manual breaker with off/on switch, easier than cutting power elsewhere IMHO, but you can pull the wires off fuel pump connections if you're on your toes when your Kubota won't stop. A real runaway diesel won't respond to either.

Alternator Breaker--I disconnected my Kubota's alternator/regulator harness--no generator battery so why use the alternator, it isn't free lunch. The alt pulley is part of the crank/waterpump belt drive. I believe the alt bearings will last a lot longer if it isn't being called on to make juice.
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Last edited by nbedinger; 07-04-2019 at 12:45 AM.
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  #10  
Old 07-03-2019
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Quote:
Originally Posted by gcyeaw View Post
What model number is the Onan. I thought the fc 35's had the Kohler/Perkins set, but may have been an option.
87 - 89 had the onan, but a very few 87 still had the kohler.
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