Cleaning Onan generator slip rings

Howdy,
I fixed my generator. Finally got a piece of time to work on it. YOU All were right. It was an overheat situation. Found a lot of mouse nest stuff directly below the circuit board. And alot elsewhere, some around the throttle / governor linkage. So I appreciate all your advice and it saved me the price of that cleaning stick. Most of all I learned a lot of good stuff from you. I thought the fuel pump was only sensitive to high temp shut off. But it makes sense that there are other temp sensors.

I took my generator problem to Cummins & they found a bad board, in my unit.

I have used the "Slick Stick" a bunch. worn a couple out. If the slip rings are only slightly oxidized/worn you can clean them. I usually cut a piece of green scotchbright pad to fit end of a paint stir stick or chopstick, tape it on with elec tape. This works well on older Emerald, Marquis, and newer 5.5 and 7 kw sets. Just remove brush block for access to rings. You dont specify what model of 4K Onan you have, but likely a 4KY Microquiet. the brushes are behind fan/flywheel and will require some disassembly to access brushes on this model

I hate to say this, but cleaning the slip rings wasn't my gen. problem, I thought after running it for 24 hours under load that it was fixed, but yesterday it quit after 20 minutes, I talked with Flight Systems today & they gave me a plan on how to check and see if the board is getting to hot, the said when it quits again to spray the board housing with key board cleaner with the can turned up side down, this will cool the board & then see if it will restart.

It wouldn't restart yesterday after it quit, but did start right up this morning.

Thats great info. Thank you. I will check the entire unit for cooling restrictions.

Hours of use and environment are the deciding factors on slip rings condition,
Generally if low run time hours and high Humidity, there is a chance of dirty slip rings,
A generator used often is less likely to have this problem,
An over heat problem is more often the problem,
air flow over the engine,
Air flow thru the generator head,
Dusty control boards retaining heat,
I would take compressed air and blow every area of that Genny clean , especially hard to reach areas inside the generator, rodent nests create air blockage and cause heat problems

As Doug points out, a gen with bad slip rings generally won't generate power at all and newer generators will not run. That load makes a difference sounds like a heat issue.

fourthclassC wrote:
Appreciate all the replies. I have not actually looked at the slip rings yet. It is a 4kwatt onan. 03 Winnebago 324v. class C. I replaced the fuel pump and filter with Onan OEM about 2 years ago. Been running and starting great since then. But recently it shuts down after about 30 mins. with the AC on. Stays running with lower draw stuff like fans going.

Usually with slip ring and BRUSH problems the Onan will not start and run at all after releasing the start button. Because the needed AC voltage signal from the Brush/Slip rings is not being generated.

Appreciate all the replies. I have not actually looked at the slip rings yet. It is a 4kwatt onan. 03 Winnebago 324v. class C. I replaced the fuel pump and filter with Onan OEM about 2 years ago. Been running and starting great since then. But recently it shuts down after about 30 mins. with the AC on. Stays running with lower draw stuff like fans going.

I've used Flight Systems Slip Stick on several different generators over the years with good results. I've never needed to drop the generator to use it. I do run the voltage/resistance checks in the Onan service manuals first though, to see if cleaning is needed. Generally, I've cleaned the slip rings on generators that have sat for extended periods without running. The most recent one I worked on had sat for about 4 years and the rings were pretty black.

Here's a video on using one:

Using the Slip Stick