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Onan HGJAB Spec A Harness


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  #1  
Old 10-06-2015, 12:40:27 PM
GenGuy1 GenGuy1 is offline
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Default Onan HGJAB Spec A Harness

Hey guys, I'm working on an Onan HGJAB Spec A 5500 Gold, will not run unless I keep the start button held. No voltage at breaker when starting, also was able to do diode test P1-1 to P1-10 and P1-3 to P-9 without any continuity. Was not able to get to any other terminals.

My question is about the breakout harness and accesory, do I need the accesory to test it or will the harness alone work? Have I don't enough to point VReg? I also cannot find the bulletin for the module test on QuickServe, does anyone have the bulletin number? I went off previous posts on here for my readings for diode test.

Thx guys
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  #2  
Old 10-06-2015, 12:50:33 PM
Kpack
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Default Re: Onan HGJAB Spec A Harness

Do you have the service manual ?
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Old 10-06-2015, 01:03:44 PM
len k len k is offline
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Default Re: Onan HGJAB Spec A Harness

With engine off, and control board disconnected, measure rotor resistance brush to brush (p1-1 to p1-10 of harness to rotor brushes) should be 29.34 ohms +- 10%. Service manual page 6-4. Check that resistance of rotor to frame is ~ 1,000,000+ ohms. Also check that brushes are not worn, loose , or sticking.

The AC voltage reg tests for Onan NHE types of measuring reg diode and resistances are only a partial test, they can't conclusively confirm a bad reg, likely same here.

Wiring schematic is on page A-3 at end of service manual.

I'm not familar with the " breakout harness and accesory" . Think I would just unplug the control board , hot wire gas pump. Not sure but don't think you have to do anything with the spark magnetos. I suspect control just grounds them to stop spark, (read service manual)


With engine running normal rpm, control board disconnected, ans 12VDC to rotor brushes, stator Q winding should have 64VAC across them , and T winding ( the 120VAC ones ) should have 39 VAC

Last edited by len k; 10-06-2015 at 01:35:21 PM. Reason: changed to say measure rotor at (p1-1 to p1-10), added test voltages
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Old 10-06-2015, 11:22:55 PM
GenGuy1 GenGuy1 is offline
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Default Re: Onan HGJAB Spec A Harness

I found the service manual the other day which talked about the harness being needed to do the tests it basically plugs into the control harness so you can get good readings. Other research pointed me to control module and vReg due to fault code 32.

I'm to the point now that I need to go back out there and in a few minutes figure out what it is. So far no literature has shown me that and all I keep hearing about is a bulletin that Cummins can't point me to and that will not show up in QuickServe and readings on this damn harness that my big hands can't get to.

I was able to get to P1-1 and P1-10 though Len, and got nothing. I guess I misspoke when I said diode test. We did have a tech go out there about 2 months back and he did clean the brushes, he was initially getting low voltage.

Are all of the readings that you are telling me about able to come from the plug? Maybe I can say screw the control module test from the bulletin and get the harnes and test the vReg instead. I am not familiar with RV gens much at all, mostly work on standbys. We are starting to see these more though. Thx for your reply
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Old 10-07-2015, 12:20:37 AM
len k len k is offline
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Default Re: Onan HGJAB Spec A Harness

Quote:
Originally Posted by GenGuy1 View Post
I was able to get to P1-1 and P1-10 though Len, and got nothing.
Those wire run from control board to brushes.

With control board disconnected and measuring between those 2 wires that run to the brushes you should be getting ~ 29 ohms. IF your getting an open circuit , I'ld retake that measurement at the brushes. IF still open circuit I'ld measure directly to the slip rings of the rotor.

If it's an open circuit then rotor isn't being energized and no way gen will make power without that. Except maybe 1-2 VAC output from residual rotor magnatism.
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Old 10-07-2015, 09:04:31 AM
Kevin K Kevin K is offline
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Default Re: Onan HGJAB Spec A Harness

Flight Systems sells a breakout box called a "G-Man" similar to what you are describing. Their "ultimate package" version has the adapters to test the HGJAB. You can download the operator manual and quick start guide from their web site.

https://www.flightsystems.com/standb...or-tester.html

The price is a bit steep for a hobbyist, but there is no doubt this tool would quickly pay for itself when used by anyone in the business of servicing Onans. Flight Systems has a very good reputation.
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Old 10-07-2015, 09:41:27 AM
pegasuspinto pegasuspinto is offline
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Default Re: Onan HGJAB Spec A Harness

First two things to check. Check that the brush holder and brushes are OK. Check to make sure that the rotor spins with the engine.

Generally, if you start the engine once and it shuts down, if you immediately re-start it will start and run, as long as it isn't a critical damage fault.
32 is low crank speed, almost certainly bad drive coupling or a bad belt. If then gen can't spin it looks like low crank speed....
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Old 10-13-2015, 12:29:49 PM
GenGuy1 GenGuy1 is offline
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Default Re: Onan HGJAB Spec A Harness

I do not believe this is the kit I saw but that is very nice, I will look into it. With more research, I believe I was testing the controller itself rather than the wires going into the generator.


I have seen that the voltage regulator is built into the controller on this unit which leads me back to my original problem in finding the bulletin to test the control board.

I see a lot of mention of the brushes and the internals but with our guy out there a few months ago all over that, I don't think its going to be the brushes. What actually senses the flywheel spinning? I know on our bigger ones it's either looking for voltage from the magnetos or it reads the teeth. Now I can't find the dang service manual.



Quote:
Originally Posted by Kevin K View Post
Flight Systems sells a breakout box called a "G-Man" similar to what you are describing. Their "ultimate package" version has the adapters to test the HGJAB. You can download the operator manual and quick start guide from their web site.

https://www.flightsystems.com/standb...or-tester.html

The price is a bit steep for a hobbyist, but there is no doubt this tool would quickly pay for itself when used by anyone in the business of servicing Onans. Flight Systems has a very good reputation.
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Old 10-13-2015, 04:56:32 PM
pegasuspinto pegasuspinto is offline
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Default Re: Onan HGJAB Spec A Harness

The generator senses the flywheel spinning through the belt and drive coupling, but only when the brushes are good enough to excite the generator to make voltage to sense through the Q windings........

pull the brush holder, then you can see them. through the same hole you can see the armature move. It should be FIRMLY in lock with the engine. If it seems to spin up slower then the engine, or spins after the engine has stopped, the belt or coupling is broke.

Once that is verified, then i suggest moving on to far less common and more expensive issues.....
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  #10  
Old 10-13-2015, 06:56:04 PM
len k len k is offline
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Default Re: Onan HGJAB Spec A Harness

(Several possibilities for no output voltage. Dead AC reg (in control board), broke mechanical rubber shaft coupling or belt, bad brushes, bad windings.

Ahh....... fault code 32 = LOW CRANKING SPEED SENSE.....page 11-21
"Prior to 2003 – quadrature frequency less than 1.7Hz for 2 continuous seconds after pressing start
After 2003 – quadrature frequency less than 1.7Hz for 12 continuous seconds after pressing start"
So it may be a sheared rubber coupling, that does happen on these. But I think that code will also show if voltage is zero (no hz)

Windings Testing & that gen rotor is spinning (coupling not broke).
A fancy harness connector is easy, quick and convenient, but likely pricey. For one time use I would just use wires to apply 12 VDC to the brushes and measure voltages (with controller unplugged), as I suggest back in post #3.

There is a mechanical gov that keeps engine rpm steady, page 9-14 of service manual.

If you need the service manual, #983-0501D, post an email and someone will send one.

Last edited by len k; 10-13-2015 at 11:37:11 PM. Reason: add code 32 paragraph
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