SPINJIM 1,984 #1 Posted June 23, 2020 Here's a question for all of you Onan gurus out there. I have a 1992 520H that had a blown engine. And I have a 1988 Onan P218 engine in good condition (from a WH 518H) with low hours that I want to put into the 520H. In comparing the two wiring harnesses and the wiring diagrams, the P218 had an 'Auxiliary Solenoid' in the starter circuit, in addition to the solenoid attached to the starter motor. The Onan P220 that was in the 520H did not have that auxiliary solenoid, and was wired directly to the starter solenoid. I have to decide which wiring harness to use, the one from the blown P220 or the one that came with the P218. I'm leaning toward using the wiring harness from the P220 to keep it compatible with the rest of the newer 1992 wiring in the 520H . But why was there an auxiliary solenoid in 1988? It was also used in the 1988 520H, and I think they all use the same starter switch. Jim Share this post Link to post Share on other sites
lynnmor 7,641 #2 Posted June 23, 2020 9 hours ago, SPINJIM said: Here's a question for all of you Onan gurus out there. I have a 1992 520H that had a blown engine. And I have a 1988 Onan P218 engine in good condition (from a WH 518H) with low hours that I want to put into the 520H. In comparing the two wiring harnesses and the wiring diagrams, the P218 had an 'Auxiliary Solenoid' in the starter circuit, in addition to the solenoid attached to the starter motor. The Onan P220 that was in the 520H did not have that auxiliary solenoid, and was wired directly to the starter solenoid. I have to decide which wiring harness to use, the one from the blown P220 or the one that came with the P218. I'm leaning toward using the wiring harness from the P220 to keep it compatible with the rest of the newer 1992 wiring in the 520H . But why was there an auxiliary solenoid in 1988? It was also used in the 1988 520H, and I think they all use the same starter switch. Jim Skip the auxiliary solenoid. The 520H has relays for the safety systems. 1 Share this post Link to post Share on other sites
SPINJIM 1,984 #3 Posted June 23, 2020 9 hours ago, lynnmor said: Skip the auxiliary solenoid. The 520H has relays for the safety systems. Kind of what I suspected, but I didn't want to take a chance of burning up the wiring or the new starter. Thanks for your help. Jim Share this post Link to post Share on other sites
