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Onan BGD Burning Out Circuit Boards


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  #1  
Old 09-16-2013, 05:20:10 PM
jd2210ct jd2210ct is offline
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Default Onan BGD Burning Out Circuit Boards

Hey All,
I have an Onan BGDF 830502 C, Serial Number H910966461 Generator that burns out the control boards. Also don't hold me to the model and serial numbers as they are almost completely gone on the label. VERY hard to read. I have done some checking into these with Flight Systems and think the circuit for fuel pump, choke heater, coil, etc is the one that fry's the board. I had one go bad and purchased a new replacement from flight systems. It worked for a short time and then stopped. I purchased another one and hooked it up to the genny. As soon as I hit the start button, it fried the board and would not stop cranking the engine until I disconnected it. Any thoughts as to where to turn would be great help.
Thanks Much
Scott
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  #2  
Old 09-16-2013, 05:46:00 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

I don't recognize middle of model number, but looks like it's BGD model , spec #C (last letter of model #).

The first thing I'ld do is check that genset is wired as per schematic in service manual. My first guess is it's not, or something board is powering is drawing too much amps (is bad) or it's power wire is loosly shorted to ground. A real good clue to what is wrong would be to look at the board and determine what is burnt out. Just out of the blue I'm guessing a relay is welded open or closed.

I'ld look at schematic and guess whats wrong, but harddrive smoked in my other computer with gen manuals. Will take a little to reload backup cds.
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Old 09-16-2013, 05:47:03 PM
Wayne 440 Wayne 440 is offline
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Default Re: Onan BGD Burning Out Circuit Boards

It seems logical to check the "fuel pump, choke heater, coil, etc..." for excessive current draw.
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Old 09-16-2013, 06:04:15 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Also check that board traces themselves are not shorting to any metal including mounting washers. Cover plate on some of these gens are metal. Also on my similar model gen there is a loose insulating peice of rectangular plastic on back of board.

I don't remember yours but some versions of this series had the board power a off-board relay that then powered pump,coil,ect. Relay could have died and someone removed it , drawing too much power from board. Some relays on some boards are only rated at 3amps.

What is gen's history?? Has gen been running normally for you in past or is it new to you?
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Old 09-16-2013, 06:13:04 PM
jd2210ct jd2210ct is offline
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Default Re: Onan BGD Burning Out Circuit Boards

OK, after checking around on this board, I believe the correct model number to be 4.5 BGDFB 3502C. This is on a bucket truck and also runs a hydraulic pump. Does anyone have any suggestions as to how to check the choke heater etc, for the proper current draw? I have a sears cheapo multi-meter, would this do the job and if so how.. I am pretty green at this generator electrical stuff. Someone will likely have to hold my hand here!!!
Thanks
Scott

Generators history is like this.. When I bought the truck, everything was working fine. One day the in bucket remote wouldn't start the generator and it began to only work once in awhile, t then it completely stopped working. Was told it was the control board, so ordered a flight systems replacement. This also worked great for a time and then failed the same way.. I ordered another replacement and hooked it up to the generator. Hit the start button and the board fried just like that and the started would not disengage until I unplugged the harness. I now have it "hot wired" by powering the fuel pump, coil, on a switch...

Thanks
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Old 09-16-2013, 06:29:50 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

I'ld start with the basics. Check that it's wired as per schematic first, especially it's new to you and you have not seen it run normally.

If you don't have a service manual someone along today.

Just saw your last post, getting called to dinner now. More latter.
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Old 09-16-2013, 06:36:25 PM
Daverepair Daverepair is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Usually you can see what trace on the board is burnt and follow that to a pin then with the wiring diagram see what is being powered by that pin. did you save the bad boards and is it the same circuit. Send the board back to flight and I am sure they will be able to tell you, us what the burnt up component feeds. Is the board not fuse protected. If it is that is another clue.
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Old 09-16-2013, 07:11:11 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Quote:
Originally Posted by jd2210ct View Post
I ordered another replacement and hooked it up to the generator. Hit the start button and the board fried just like that and the started would not disengage until I unplugged the harness.
Unplugged the harness..... if harness is to remote switch maybe that truck wiring is damaged or shorted to ground. The start stop switch grounds one of 2 wires to make it start/stop. Wouldn't expect that to fail the board though. Usually with remote wiring unplugged if gen runs normal using gen mounted switch problem is not in gen. But some commercial gens have an extra pair of wires for security lockout switch.

I need to look at schematic before I comment more.
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Old 09-16-2013, 08:02:04 PM
jd2210ct jd2210ct is offline
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Default Re: Onan BGD Burning Out Circuit Boards

I did have the remote unplugged when I installed the new board... Pretty sure the problem is not there as it burned up without it being plugged in...

Thanks

Quote:
Originally Posted by Daverepair View Post
Usually you can see what trace on the board is burnt and follow that to a pin then with the wiring diagram see what is being powered by that pin. did you save the bad boards and is it the same circuit. Send the board back to flight and I am sure they will be able to tell you, us what the burnt up component feeds. Is the board not fuse protected. If it is that is another clue.
The trace goes to pin #12 as I see it on the board which looks like it runs to what looks like a diode labeled CR3.. Not sure if this helps..

Thanks Scott
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  #10  
Old 09-16-2013, 08:09:29 PM
Kpack
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Default Re: Onan BGD Burning Out Circuit Boards

Here's a old posted manual from you Len. Didn't know if you still had it. I don't know if the wiring diagram would match a comercial unit.
http://www.cumminsonan.com/www/pdf/manuals/965-0529.pdf
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  #11  
Old 09-16-2013, 08:24:29 PM
jd2210ct jd2210ct is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Thanks much for the manual link... Will be doing some testing in the morning.. I am going to try and attach a photo of the board...
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  #12  
Old 09-16-2013, 09:05:53 PM
JerryLee JerryLee is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Something is drawing wayyyyyy too much current there. You can probably repair this board just by soldering an insulated wire from one end of the burned trace to the other end of the burned trace. Pick a point where the trace is connecting with a component leg sticking thru the circuit board.

I would be tempted to use a fuse holder with a 1 amp fuse and pigtails on each end as my jumper wire.

Next thing is to find where the problem is.........why is this circuit drawing so much current. Do this before you apply power again. The conductor may be shorting to ground. Use your ohm meter to see what's happening. Only apply power to the board after you find the source of the problem.
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Old 09-16-2013, 09:13:57 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Kpack thank you for the manual would have taken a bit to load manuals, back is still ~~~.

The loose trace definitely looks like it was over-currented. Green coating was vaporized off as trace got hot. Looks typical of burned trace.

Wiring diagrams are at end of manual. The one you use depend on the spec number of your gen. Spec # is last letter of model number, you previously listed it as "C" so that looks like diagram on pfd page 105 of Kpack's manual #965-0529

One thing I noticed is some versions of this gen likely don't use a 12V fuel pump (maybe 6V) because of series resistor r7. If 6volt pump and no resistor that could do it. Never know what previous owner did.

I also notice page 105 circuit show CR3 connecting to pins 3 and 6. you said pin 12.Gen may not be spec C, I'll have to look at my cd's tomorrow.

You can repair board by soldering wire. But solve the problem that is causing this first or something else on board will fail like a diode for relay. Trace acted as fuse for you.
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Old 09-16-2013, 10:05:41 PM
jd2210ct jd2210ct is offline
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Default Re: Onan BGD Burning Out Circuit Boards

OK, I just went out and stuck the meter on my "hotwire" at the fuse holder and checked the current draw. With power to the fuel pump and coil, it shows .95 amps draw. When I hit the start button, it jumps to 2.35 amps and stays in that area while it's running. Is that high? Tomorrow I will check the choke heater in the morning...
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Old 09-19-2013, 12:02:49 AM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

I'm back, didn't forget about you. Second computer I was using died, got 1-st one working again. ( Had "blue screen of death". Used harddrive diagnostics disk to recover from harddrive errors, old drive).

I didn't measure my amps, but 2.35 A don't sound reasonable. See if a sharp edge of sheet metal has worn a hole in wire's insualtion and it's intermitantly shorting out.

I'll look more at schematics tomorow.
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Old 09-19-2013, 01:02:16 AM
FSmyth FSmyth is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Quote:
Originally Posted by jd2210ct View Post
OK, I just went out and stuck the meter on my "hotwire" at the fuse holder and checked the current draw. With power to the fuel pump and coil, it shows .95 amps draw. When I hit the start button, it jumps to 2.35 amps and stays in that area while it's running. Is that high? Tomorrow I will check the choke heater in the morning...
Probably not out of line for a running system.
If that pin is truly pin 12, it's only function is to run the fuel pump (or relay).
Find the pinched or bare wire to the pump.
The diode (CR3) may not have lived thru the short, but should be easily
replaced. The manual did not include a parts list, but any 3A replacement
should work. Solder a wire back over the trace (doesn't have to be real
heavy; a piece of AWG 14 is plenty.
<als>
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Old 09-19-2013, 12:14:16 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

Typo..... meant to say .....I didn't measure my amps, but 2.35 A don't sound unreasonable.

Yes any diodes supplying that trace should eventually be checked, was little surprised any diodes conducted enough current to fry trace and lived. But first have to determine what drew all that current, I'm guessing > ~10 amps. I'ld guess shorts on wires trace supplys.
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Old 09-19-2013, 02:22:06 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

You say model number is BGDF 830502 C or 4.5 BGDFB 3502C. The last letter of model # is spec # (version #) , that would make it spec C. But maual schematic for spec C shows a board with 3 connectors and fuel pump supplied by board pin p3-6, you say it's supplied by pin 12 and your picture shows a 2 connector board.

So I think you have a gen that is newer than spec C . And schematic in manual 965-0529pfd page 101 is applicable. Not sure why it comtinues to crank, sounds like one of board relay contacts welded shut. To burn that trace I suspect it carried 10-20 amps, wires that trace supplied have to be grounded somewhere, maybe intermitantly.

To test coil and pump with your hot wire setup, can put small fuse in series with each of coil and pump to look for intermitant internal shorts to ground.

Does harness wiring to board connector look factory or are they all spliced and taped.?
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Old 10-05-2013, 10:52:37 PM
jd2210ct jd2210ct is offline
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Default Re: Onan BGD Burning Out Circuit Boards

OK, so after doing some more research and testing, I've concluded that my "hotwire" job is what fried my new board!!! Now the one other board I had that was also fried has been patched up and will run the generator until you release the start switch. So this means I am getting no current from the generator to close the relays and keep it going... What do you all suggest I look at now???? Thanks for all the tips and info... Scott
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Old 10-06-2013, 04:17:51 PM
len k len k is offline
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Default Re: Onan BGD Burning Out Circuit Boards

This gen is just like Onan BGE. Usually the gen sits unrun for 2-3 months and sliprings get dirty/oxidized and develope high contact resistance to brushes. Then when you run the gen the electronic voltage regulator (VR1) dies. The reg is what supplies power to rotor to make AC.

Before you replace reg do some testing .
Check that control board flashes VR1 with +12V thru pin 7 when you press start button.

Also test windings.... remove regulator and measure rotor resistance thru brushes should be 20-25 ohms. If higher clean slip rings with scothbrite pad. Also check ohms from brush to frame should be > ~1,000,000 ohms, insulation test.

Once clean do preformance test on windings....remove reg, hotwire coil and gas pump to run engine, apply 12VDC across brushes, measure stator winding voltages. Should have: 40-50VAC across T windings, 55-60 across Q, ~ 6.5 across B. Can also test insulation of Q and B winding, should be > ~1,000,000 ohms to ground with reg and control board disconnected. Tell us what you find.

If need reg , I recomend Flight Systems http://www.flightsystems.com/ , good reg and good bunch of guys and cheaper than Onan.
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