Onan Generator troubles

Question

Hi all,I have an Onan microquiet 4000 generator. It seems to be going through brushes over the last few years. Only 1 brush wears out. I replace them and everything works fine for awhile. This last time, I noticed the slip ring on the one that wears out was worn so I thought I would replace it. I also replaced the rotor since I found some posts that say it goes bad. After the replacement, the generator started and ran. I shut it off and changed the oil. I restarted it and was letting it run while I cleaned up tools and such. It stopped after 10 minues. I tried it restart it got a code 32, low cranking speed. I took it back apart to see if anything went wrong. I didn't see anything, checked the rotor and stator. Both checked out fine. I ordered a new board, same issue. I read something about checking brush alignment using PSB-682a. I can't find this procedure. Anyone have it? Or ideas on why my generator starts and stalls with code 32?

newman_fulltime · Answer

very good chance a bad battery is causing the stall

allbrandauto · Answer

my onan 5500 did the same thing 1 brush would wear I to replaced the rotor cutting off after 10 minutes sounds like the fuel pump take cover off and push prime button do you hear fuel pump clicking if not take a 12 volt test light 1 of the 2 wires at pump should be 12 volts while pushing down prime button if yes pump is bad

mrbishop · Answer

thanks for the suggestions. Battery is good and fuel pump is good, fuel level in coach is 3/4. We run those fuel pump on our race cars, very familiar with them.

The board is shutting it down, according to the manual, because it does not see voltage right away. I just don't have a good way to know what is going normal on each circuit. I got the new board from flight systems. I just saw they have a free diagnostic help, I am going to contact them. I am sure it is something silly, just hard to diagnose.

onan · Answer

Your brush wear and FC32 seem to be telling you that the generator brushes or possibly brush block are having issues. Bulletin 682 talks about how to inspect and correct alignment. The control uses the input through the brushes to determine rotation speed at crank. Below is text from 682 bulletin.

HGJAx
Remove the cover and using a flashlight inspect the brush to slip ring contact thru the openings in the endbell. A sign of brush wear on the white insulation indicates possible misalignment. Check the field resistance between the brushes, F1 & F2. The resistance should be 31.97 ohms (+ -) 10%. If field resistance is out of spec and or poor brush alignment is evident, the generator must be disassembled to repair.

You didnt state hours for brush wear, but rapid and inconsistent brush wear is a sign something is out of whack between collector ring and brush.

mrbishop · Answer

Hi Onan.The problem is I can't find the bulletin. Do you have a link to it? I had realigned them but I like to make sure what I did it what the manufacturer wanted. They were kinda of off to one side a few brush changes ago and I shimmed it so they are in the center of the slip rings. The one slip ring had wear so hopefully I am good for some time. All ohm readings were OK at the components.I actually found my problem today. Pin J1-3 had been pushed out from all the disconnects. The latch that holds the terminal in place is not holding any more. Odd that it did it in the middle of running. Must have broke and then vibrated out. The seal has also swollen and won't re-install. It is running right now, hopefully it will be when I go back out.Off to find a new connector end.

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