| No joy Genny (Onan woes) [message #213553] |
Sat, 06 July 2013 21:10  |
Mike Teets
Messages: 299
Registered: January 2004
Location: Dublin, OH
Karma: 0
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Today, I pulled the Onan 6kw power drawer so I could get to the back side and clean it up and see what is going on. It came out easily as a previous owner had even attached the remote panel with a trailer plug. Yeah previous owner!!! I remembered a box with an air Onan air filter from the previous owner. Pulled out the box and found a new set of (4) brushes, and a new OEM bridge rectifier with the correct pin out in boxes.
I found that the brush holders were quite dirty and the brushes were not sliding up and down. I removed the units, cleaned them thoroughly and put them back together. I compared my old brushes to the new and they were almost the same size so I put the old ones back in. I installed the NOS bridge rectifier after bench testing it and ensuring it went in the correct direction. My plastic plug has +/-/F1/F2 marked on the back side.
I tried pulling the back bell housing off but it was not budging and I didn't want to risk breaking it. Tried the plastic hammer method in the maintenance manual but it appears to be stuck on the shaft. I was unable to test the armature outside of the unit.
Put everything back together and the unit fires up with a touch of the switch. But... still zero volts output measured at the generator and inside when connected to the coach.
Any suggestions?
Mike, Dublin OH
Mike, GMCing since 2002
77 Palm Beach, 260, 403
Dublin, OH
http://teamteets.com/gmc/
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| Re: No joy Genny (Onan woes) [message #213556 is a reply to message #213555] |
Sat, 06 July 2013 22:09  |
Mike Teets
Messages: 299
Registered: January 2004
Location: Dublin, OH
Karma: 0
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Senior Member |
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Thanks A. I was able to test all of that except the armature. The manual says that it must be tested outside of the unit. I do have continuity through the armature so it is not open/broken connection.
I seem to remember something about them loosing their polarity or something if they set for too long. Something about jumping the field. I just can't find that reference.
Mike
Mike, GMCing since 2002
77 Palm Beach, 260, 403
Dublin, OH
http://teamteets.com/gmc/
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| Re: No joy Genny (Onan woes) [message #213557 is a reply to message #213556] |
Sat, 06 July 2013 22:27 |
Mike Teets
Messages: 299
Registered: January 2004
Location: Dublin, OH
Karma: 0
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Found the magnetism reference by poking around GMCWS, Duane Simmons troubleshooting guide... I will give that a try tomorrow.
• HIGH SUSPECT IS FAILED BRIDGE RECTIFIER (BR):
REPLACE/ADAPT W/HIGHER VOLTAGE RATED BR (NTE 5328 OR EQUIVALENT)
NOT PIN COMPATIBLE & REQUIRES BASE MODIFICATION TO ALLOW INDIVIDUAL WIRE ATTACHEMENT
- SEE GMC MAINTENANCE MANUAL FOR BR TEST METHOD
• ONAN CIRCUIT BREAKER FAILURE:
REPLACE/ADAPT BUTTON TYPE W/MORE RELIABLE UNIT (GE/WESTINGHOUSE
“QUIK LAG” TYPE @ 40 OR 50 AMP.)
- PROBE EACH CB WIRE TERMINAL W/RESPECT TO CHASSIS GROUND TO DETERMINE IF AC IS PRESENT
• LOSS OF RESIDUAL MAGNETISUM:
DISASSEMBLY OR ELECTRICAL FAULT MAY CAUSE LOSS/REVERSAL OF RESIDUAL MAGNETISUM
- POLARIZE MAGNET BY A FLASH/MONENTARY CURRENT FLOW INTO FIELD WINDING:
- REMOVE BR & APPLY FLASH/MONENTARY BATTERY + VOLTAGE TO THE FIELD + WIRE & CHASSIS (-) VOLTAGE TO FIELD NEGATIVE (–) WIRE (MONENTARY ONLY)
• BRUSH FAILURE: SEE GMC MAINTENANCE MANUAL FOR DETAILS
NOTE: THE CONTROL BOARD IS FOR ENGINE OPERATION ONLY & HAS NOTHING
TO DO WITH AC POWER GENERATION
Mike, GMCing since 2002
77 Palm Beach, 260, 403
Dublin, OH
http://teamteets.com/gmc/
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| Re: No joy Genny (Onan woes) [message #213593 is a reply to message #213553] |
Sun, 07 July 2013 10:30 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Mike Teets wrote on Sat, 06 July 2013 22:10 |
Today, I pulled the Onan 6kw power drawer so I could get to the back side and clean it up and see what is going on. It came out easily as a previous owner had even attached the remote panel with a trailer plug. Yeah previous owner!!! I remembered a box with an air Onan air filter from the previous owner. Pulled out the box and found a new set of (4) brushes, and a new OEM bridge rectifier with the correct pin out in boxes.
I found that the brush holders were quite dirty and the brushes were not sliding up and down. I removed the units, cleaned them thoroughly and put them back together. I compared my old brushes to the new and they were almost the same size so I put the old ones back in. I installed the NOS bridge rectifier after bench testing it and ensuring it went in the correct direction. My plastic plug has +/-/F1/F2 marked on the back side.
I tried pulling the back bell housing off but it was not budging and I didn't want to risk breaking it. Tried the plastic hammer method in the maintenance manual but it appears to be stuck on the shaft. I was unable to test the armature outside of the unit.
Put everything back together and the unit fires up with a touch of the switch. But... still zero volts output measured at the generator and inside when connected to the coach.
Any suggestions?
Mike, Dublin OH
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Mike,
There is an unfortunate issue with old Onans. The aluminum wire used for the field corrodes open. The +/- leads on the rectifier should go to the field. Confirm this and then check the field resistance. If it is far from 30, then you need to get in touch with both Jim Miller and Bill Michel on this list. Jim is trying to set up to rewind fields and Bill has someone that will but geography is an issue.
If you need to flash the field to bring up enough residual to get the machine to cascade to life, get Jim to walk you though it. He is in Hamilton and it might well be worth your drive over there to get his assistance.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: No joy Genny (Onan woes) [message #213634 is a reply to message #213593] |
Sun, 07 July 2013 18:39 |
Mike Teets
Messages: 299
Registered: January 2004
Location: Dublin, OH
Karma: 0
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Senior Member |
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No more luck today...
Tried to magnetize the field according to Duane Simmons write ups and verified elsewhere on the web. No effect.
Tested again and I still see 0 ohms resistance between F1 and F2 with the bridge removed. Jim Miller says this is a very, very unlikely failure. I do NOT see any continuity between F1 and the chasis or F2 and the chasis with the test on 39 of the major service manual. The leads from F1 and F2 go through separate single pole plug connectors into the field wires. Plenty of slack and both test as good connections. The leads into the field are tightly zip tied to the field loops, as shown in the manual, and do not appear bad or disturbed.
It seems I must have a dead short in the windings. Although I do wonder why I didn't see sparking or hot wires when I did the field magnetizing.
Mike, Dublin OH
77 PB, 403
teamteets.com/GMC
Mike, GMCing since 2002
77 Palm Beach, 260, 403
Dublin, OH
http://teamteets.com/gmc/
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| Re: [GMCnet] No joy Genny (Onan woes) [message #213677 is a reply to message #213634] |
Mon, 08 July 2013 08:26 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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On Jul 7, 2013, at 7:39 PM, Mike Teets wrote:
> Tested again and I still see 0 ohms resistance between F1 and F2 with the bridge removed.
Mike,
You'll be wasting your effort worrying about the armature or anything else until you figure out why you are not reading the proper resistance (38 ohms) between F1 and F2. This resistance is CRITICAL for the proper functioning of the excitation/voltage regulator mechanism. The field contains just over half a mile of aluminum wire with a resistance of ~10 ohms per thousand feet. If you are reading 0 ohms then the fault cannot be too far into the windings distance-wise.
I am wondering if the labeling on the wires is incorrect; you said your PO had messed around in there? I can believe ~0 ohms looking into the compounding reactor but I cannot believe 0 ohms across the field leads under any circumstances.
--Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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