| Troubleshooting the Onan control board and LOP switch [message #169671] |
Mon, 14 May 2012 22:33  |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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The latest challenge on my GMC is to get the Onan working again. I purchased a Dinosaur control board from JimK about a year or so ago, and the Onan ran fine for a while (except for occasionally stalling, which is a separate issue). But now it refuses to continue running after the I let up on the Start switch.
I went through the troubleshooting steps at http://gmcmotorhome.info/generator.html#Starting. The Onan runs when I jumper terminals 9 and 5, and all of the voltages across terminals 10 and 1, 11 and 1, 8 and 11, and across the fuse all check out. I had previously disconnected the alternator/battery charger, and the Onan ran fine without it. It also has plenty of oil.
I tried to go through the LOP switch tests at http://gmcmotorhome.info/generator.html#switch, but I can't disconnect terminal 12 because the board I purchased has all of the pigtail wires soldered in place. Is there a way to test the LOP switch without removing terminal 12?
And as always, thanks for all of your help!
-B
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: Troubleshooting the Onan control board and LOP switch [message #169682 is a reply to message #169680] |
Mon, 14 May 2012 23:22  |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| Ken Burton wrote on Mon, 14 May 2012 21:17 |
Unplug the wire on the LOP a the switch.
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Just make sure the wire remains isolated from everything... including ground.
The oil pressure switch applies a ground when the oil pressure is low. So if the disconnected wire is touching something that provides a low resistance to ground.... you get the idea.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Troubleshooting the Onan control board and LOP switch [message #169684 is a reply to message #169680] |
Mon, 14 May 2012 23:26 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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We had a discussion at Bean station about those Dinosaur boards.
One of the people at BS complained enough direct to Dinosaur that they made a mod the to a new board and sent it to him. One of the comments he received when talking the the technician was they have a high number of these boards returned. The fix he had them do was to change the resistor in series with the up to speed relay from 10 ohms to 23.5 ohms (two 47 ohm resistors in Parallel). He is still testing the "fixed" board and has no problems with it. He previously went through 3 boards from Dinosaur.
You can check the switch but I suspect that you have a bad relay and need to call and then return the board to Dinosaur.
I would call them.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Troubleshooting the Onan control board and LOP switch [message #169685 is a reply to message #169682] |
Mon, 14 May 2012 23:33 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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I removed the LOP wire. With the Onan off, the resistance across the LOP switch was around 5 ohms (if I'm reading my digital multimeter correctly). I jumpered terminals 5 and 9, started it up, and the resistance went to 1, which I believe is infinity on this particular multimeter. I tried starting the Onan with the LOP switch disconnected and the wire not touching anything. Same problem--it turns over and starts, but stops as soon as I let up on the Start switch.
Bad board again?
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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