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Old 07-12-2015, 03:17 PM   #1
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1978 28' Argosy 28
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Onan 4.0 BFA generator help please

Hey group. I have a '78 Argosy Moho with a Onan 4.0 BFA spec 160004 series generator. Genset runs well, but stopped powering the 110v system last week.
backstory. I'm new to the RV world, purchasing this moho just a few months ago. When I purchased the RV the generator worked fine powering the interior system. (house a/c etc all worked great off generator). I left the A/C on high at one time when I turned the generator off. When I turned it back on, although the generator ran fine, nothing worked inside. It appears I tripped the 50A breaker on the side of the generator, which I reset. I also bypassed the 50A breaker to see if it was bad. No luck. Its good. I also purchased and installed a new 110v 3 prong plug where you plug into the genset while not on shore power. No luck here. The plug is good. The two ignition fuses are good. I don't see any blown fuses, connections etc. anywhere. All the 110v circuit breakers inside the motorhome are functioning and none were tripped ever.

But.. I'm not getting juice to the system. Any thoughts on things I could check? I have an ohm meter but am no electrician. I can walk through testing circuits if someone gives me directions. Oh, also, the 110 system works great when connected to shore power. Its just not getting anything from the genny.

Help! Thanks.
Ben
Austin, TX
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Old 07-12-2015, 08:15 PM   #2
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Ben,

Here are links to the manuals I have for the 4.0 BFA generator.

BFA Installation manual

BFA Installation manual

BFA Service manual


These manuals may not be 100% accurate for your generator but should be close enough to help figure things out. I picked up the same generator a few years ago that I plan on using as a backup generator for my house.

First off I'm not sure that 50 amp reset should be that large. The BFA is a 30 amp generator and I think the manual shows a 30 amp reset. Also a 50 amp breaker is to large as well.

Someone has done a bunch of wiring mods to your genset which will make troubleshooting a little more difficult but not impossible

Where are you checking for voltage from the generator?

Does your coach use a transfer switch or do you move a plug to connect the generator to the coach 120 system?

We'll get this figured out, it'll just take a little time

Brad
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Old 07-13-2015, 06:18 AM   #3
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Wow, great collection of knowledge on the onan 4.0 Brad. Awesome.
Pg 41 of the service manual has a troubleshooting guide. I'll go check the brushes tonight.
Per your questions: Checking Voltage- I only checked via it not running the 110v system when plugged in and the system runs on shore power. So, I know power isn't getting to the plug from the Genny. My owners manual shows the power cord going directly from the genny to the power outlet, so I'm pretty sure the genny itself is not producing anything. Thats my method of deduction. No ohm meter tests.
No transfer switch on my moho. I need to physically plug/unplug the power cord to the genny recepticle.

I made an error. Need to look at the camper breaker box tonight, but I'm pretty sure it has 1 30A breaker and 2 20A breakers. No 50A.
The genny reset says 50A as seen in the picture. Its a little white box about an inch around and 1/4" thick. I did unscrew the wires and bolt them together to bypass this breaker. Still no 110v power, so I'm assuming its still good.
I'll keep sorting through the manuals and see what else I can check this evening.
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Old 07-13-2015, 06:45 AM   #4
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Amazon.com: Blue Sea Systems Push Button Reset Only Quick Connect 30A Circuit Breaker: Sports & Outdoors

Gotta love Amazon.
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Old 07-13-2015, 07:19 AM   #5
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Ben,

You listed the generator spec as 160004. Is there a chance that it's actually 16004 with possibly a letter after the 4?

Actually could you provide all of the data plate info.
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Old 07-13-2015, 07:29 AM   #6
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ID:	242838heres the manual I have. I'm assuming it's original 1978 print. I'll be able to check the physical unit tonight for the number.
Yep, I'll get a hi res data plate shot tonight. Or, maybe I can get the wife to run out there quick.
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Old 07-13-2015, 08:17 AM   #7
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16004a
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Old 07-13-2015, 09:28 AM   #8
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I had one of those in my Argosy MH, and a 6000 watt version in my 310 MH.

I know you said you have checked the push button circuit breaker (s) but my experience is that they are the weakest link on that generator series, so do check them and their associated wiring again and very carefully. I finally replaced them on my 6000 watt one with a set of regular home breakers in a new electrical box.

And also check the little glass fuses and their holders. They also cause problems, and the fuses are good but the holders are not.

I am not clear where you checked the output voltage. Find where the power leaves the generator and check it there. With all the movement over time, the wires can fatigue and break between the generator and the outlet you plug the power cord into. The outlet sometimes is the problem too.

It most likely is something of that sort, and can be hard to find sometimes.
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Old 07-13-2015, 12:02 PM   #9
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Thanks. I"ll give everything another going over tonight. I replaced the receptacle, so I know that isn't it. I have not chased the wires where they leave the generator. Very possible something came loose or broke. As test, I bypassed the 50A breaker on the genny with no success. Its good.
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Old 07-13-2015, 12:08 PM   #10
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Ben,

After checking, the manuals I linked to above should be correct for your 1600a spec generator. Your particular wiring diagram is found on page 33 of the service manual. You'll find that the manual doesn't necessarily cover all aspects of your particular generator. Fortunately they are similar enough that shouldn't be a problem.

Not a whole lot that affects the ability of the genset to produce AC power. I will be surprised if it has anything to do with a brush or brush holder. Most likely it's in one of the connections dealing with the circuit breaker(s) or Fuse #2.

Idroba is right about the fuse holders. I've had similar issues with them so even if the fuse looks good it doesn't mean current is getting through the fuse.

Oh yeah, one other thought. Check all of the ground connections closely. If the neutral connection to ground is bad you won't get a 120vac reading. You'll probably get a much lower value (half or less).

Good luck!

Brad
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Old 07-13-2015, 12:43 PM   #11
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Ben,

I just discussed the issue with one of the electrical engineers I work with. Based on your description on how you had turned the generator off with the A/C on high it's possible that a something may have been damaged in the circuit that provides excitation to the generator.

If you look at the schematic on page 33 generator head (G1) you'll see R1, communtator, ser fld and shunt fld. If you have no DC voltage at the point where the ser fld and R1 junction then the generator would not get the excitation it needs.

This leads to the possibility that one or more of the contacts on relay K1 are bad (from over current when you shut down), resistor R1 is open or ser fld (serial field) is open.

Bottom line is your trouble shooting efforts just got more difficult

Brad
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Old 07-13-2015, 02:36 PM   #12
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Well, I wouldn't want this to be boring, now would I?
I'll do what I can tonight and give a report in the morning. Taking the beast in for brakes tomorrow, so I'll be a few days without the genny. Was hoping to have it diagnosed and any applicable parts on order but.. that would be to easy.
Thanks for the great feedback everyone. I'm hoping to get the generator running and tuned up in the next 10 days or so for a roadtrip to MN. having some house A/C when its 95 outside might be nice.
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Old 07-14-2015, 08:45 AM   #13
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Well. I hope I'm an idiot.
I only had an hour of light last night after I put the kiddos to bed. Just enough time to check all the connections again under the motorhome for disconnects/breaks in the cables. Idroba, I was basically doing what you suggested as a first course of action. Then move on to serious testing. Maybe something came unhooked from the Generator. From underneath I followed the AC current cable to.. inside the motorhome. It entered underneath one of the rear beds, just behind the wheel well. I had thought the cables ran directly from the genny, underneath, to the receptical. Nope. Low and behold when I pulled up the storage trunion under the bed, there was a 20Amp breaker, which, I believe, was tripped. Grr....
Unfortunately my house battery is dead, so I wasn't able to start the genny and test last night. I dropped off the moho this morning for brakes. I'll get to see if the generator works tomorrow or Thurs. I'm assuming it will with a fresh battery.
At LEAST I learned this lesson while at home in the driveway. Know your electrical system, how it functions, and where everything is.
I'll post up again once I get to physically test it.
Doah....

Another vintage motorhome at the brake shop that I parked next too. Cool old rig.
Ben
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Old 07-14-2015, 10:03 AM   #14
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Quote:
Originally Posted by bpg_austin View Post
Well. I hope I'm an idiot.
Personally, I hope you're not...

But I can understand how you might feel that way, heck I feel that way most the time myself
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