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Old 05-29-2017, 05:44 AM   #1
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Onan 5 KW Generator help

I have a Onan 5MDKBH 5 KW genset that has stopped working properly. It starts fine, runs for 15 seconds and shuts down. The Flashing lights indicate a 'No raw water flow' message, buy I have good flow.
I've replaced the impeller, checked the hoses and heat exchanger and all looks good.
I suspect a Raw water sensor, but can't find one anywhere and no mention in my parts manual.
Any ideas?

OR, does anyone know of Onan service between Midway Marina on the Tenn/Tom and Watts Bar Lake in East Tennessee?

Thanks,

Wm Mayberry
OPTIMYSTIQUE
Mariner 40

Heading North on the Tennessee Tombigbee Waterway
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Old 05-29-2017, 08:30 AM   #2
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Some Onans use a water pressure switch. Looks like an oil pressure switch but is tee'd into raw water plumbing. Prone to fail from corrosion. Not sure where it might be located on that machine.
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Old 05-30-2017, 05:55 AM   #3
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Thanks Ski.
I'll check and see what I can find.
There is nothing from the thru hull to the strainer, to the pump, to the heat exchanger. Maybe something after.


I can find diesel mechanics along the way, but I'm hoping there is Cummins/Onan service somewhere along the Tennessee River.


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Old 05-30-2017, 06:21 AM   #4
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As I am always curious about mechanical issues, I decided to go looking for an online manual for your MDKBH generator. They are surprisingly difficult to find.
I did find a parts manual here though. http://www.gemo-online.de/pdf/onan/MDKBH_parts.pdf

I believe that part number 12 is what you are looking for.
Good luck,
Bruce
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Old 05-30-2017, 06:47 AM   #5
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Great,
I'll dig into it in few minutes and see if I can find that sensor.
Thanks,
Wm
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Old 05-30-2017, 09:04 AM   #6
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Is there water coming out of the exhaust? If not, it's a pump or restriction, if it is it probably is the sensor.
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Old 05-30-2017, 12:56 PM   #7
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That worked!

I found the pressure sensor/switch. I checked with my service guys in Bradenton, FL and they agreed. I then checked to see if I needed to just unplug the 2 wires from the sensor or connect them. After a call to 'Diesel Don', the correct answer was disconnect them. I did and she now runs fine.
I'll get a replacement sensor on order and now we're good to go.

Thanks!

Wm Mayberry
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Aqua Yacht Harbor
Iuka, MS
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Old 05-30-2017, 01:14 PM   #8
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That is what I love about this forum. Get a great answer that fixes the problem.
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Old 06-03-2017, 02:27 AM   #9
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I had the exact same issue with the same model genset. Sorry I didn't see this thread sooner. My local Onan man advised those sensors can be a little problematic but as you have discovered, they can be bypassed (with caution).

Ryan
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