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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15006
Experience:  Certified on Onan and Generac generators
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Customer brought in a onan model no: 5.5hgjad-2558c mounted

Customer Question

hi, customer brought in a onan model no: 5.5hgjad-2558c mounted to the back of a bucket truck. hold start button, throttle snaps open, engine starts and runs at full throttle until we shut it down, then throttle snaps shut. we pulled a code 19 and replaced the govenor. now we get a code 37 and it still runs full throttle. any suggestions?
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
we just discovered that if we unplug one of several things and try to start it, it will start then die. and when we reconnect whatever was disconnected, it will start and idle correctly until we shut it off and restart it. then it will run at full throttle again.
Expert:  Hank F. replied 1 year ago.

Hello, my name is ***** ***** I am going to assist you with this.

Code 37 is Invalid Set Configuration.

Here is what you need to do first.

Directly above your control panel, mounted into the side of the generator toward the top, is a small plastic piece with 2 wires attached to it, held in with a single 10mm bolt. This is the brush holder.

Watching which wire goes where, disconnect them both.

Set your meter to ohms and connect one lead to each terminal of the brush holder. You should get a reading of about 30 ohms.

Now remove the brush holder - remove the 10 mm bolt and pull the holder straight out. Sometimes they fit pretty snug, and you need to wiggle it as you pull it out.

Check the brushes. They should be worn into an even arch pattern, and should not be chipped or cracked.

They should slide freely into and out of the holder. If they stick or bind, clean the holder with electrical contact cleaner.

The brushes should both be at least 7/16" long.

Now look inside the hole where the holder was.

You will see 2 metal bands that the brushes ride against. These are the slip rings.

The slip rings are made of copper, and should be fairly shiny.

You will see the wear pattern from the brushes on the slip rings.

The wear pattern should be pretty well centered vertically on the slip rings.

If one or both brushes are riding off the edge of the slip rings, this is a serious issue that must be addressed.

If the slip rings are dirty, they need to be cleaned by attaching a piece of scotch brite or 400 grit sandpaper to the end of a small stick.

Press the scotch brite to the rings, and press and hold start for a few seconds.

Do not hold start for more than about 10 seconds at a time without stopping to let the starter cool for a few minutes.

Once the rings are clean, ohm across them. They should read about 30 ohms.

Now use a strong flashlight to watch the rings as you press and hold the start button for 3-5 seconds.

The slip rings should start turning at the exact same time as the engine, should turn at the same speed as the engine, and should stop turning at the same time as the engine.

If they do not, you have a drive issue that we must diagnose.

Once the rings are clean, and if everything checks good, reinstall the holder.

Set your meter to VDC, and connect the positive lead to the wire that was connected to the lower brush holder terminal. This wire will be marked F+.

Connect the negative lead to the upper brush holder terminal. This wire will be marked F-.

Press and hold 'Start' for 3-5 seconds, and note the voltage.

How does all of this check out?


Customer: replied 1 year ago.
thank you for your response hank,
i checked the resistance, i got 30.4 ohms. i removed and checked the brushes. they look good, slide free and are just under an inch long. i cleaned the rings, they were a little dirty. i reassembled and checked the voltage. i got 12 volts. but now sometimes i get a code 45 and sometimes a code 37 and it still idles high. 45 and 37 seem to set depending on if i start it with those wires unplugged or plugged in. if i disconnect the throttle body wire, then ill get a code 19. reconnect and restart and still a 19, no more 45 or 37. but regardless, still idles full throttle. what do i do from here?
Expert:  Hank F. replied 1 year ago.

Code 45 is Speed Sense Fault.

Both 37 and 45 are dependant on the frequency of the AC output.

What do you get?