[Sean Marconette]

Rich,
Well as you stated the new brushes did not change anything. We went to the track Saturday and after running the generator for 7 hrs and shutting it off to leave the track for an hour. We came back and it would not run for more than 10-15 seconds and code 37. We gave up on staying the night at the track and came home. Sunday I pulled it out of the trailer and disassembled. I verified the fan and belt was fine, No debris in the fan, or anywhere. The magnetos had .015" for air gap. I cleaned the rust from the flywheel lands, and cleaned the flywheel magnet with scotch bright. I reset the air gap to .012".

I verified the wiring had the same reading at the pins for P-15 and P-20 on the magneto kill lead with the + lead to chassis ground and - lead to pin P-15 and P-20.

The following readings were taken on each magneto: Left measured 20,100 ohms, the primary measured 326.5 K ohms. The right measured 20,200 ohms, the primary measured 323.7 K ohms.

Windings measured: T1-T2 = .50 ohms, T3-T4 = .50 ohms
Q1-Q2 = 2.60 ohms

Slip rings measured 31.3 Ohms on the slip rings.
Brushes on the slip rings measured 36.6 ohms

Every measurement is close to what the Onan service manual 983-0501D, 01-06 calls for.

So I reassembled the generator and with it outside of the trailer but using the trailer fuel tank, fuel pump and battery, I ran the generator for an hour, shut it off and let it set for 30 min. It restarted and ran fine, Voltage was 120.6 VAC, 60.5 Hz, this is with no load. Shut it off and waited 15 min and same thing. It starts and runs for 10-15 sec and code 37.

So with everything hot, rechecked stator and brushes.
Q1-Q2= 2.90 ohms
Brushes = 36.0 ohms

All readings taken using a Fluke 87 DVM

I am at a loss as to what else to even look at. It runs fine until it is shut off and then will not restart while hot for more than 15 sec before shutting down on code 37. Unit will not restart, and continue to run until everything cools all the back down to ambient temperature. The only thing I come up with is the module is the problem and is faulting from heat. Do you have any other thoughts of what to try or measure?
The generator is an HGJAB 7.0 kW

Thanks for your help Rich

Sean