seuadr 488 #1 Posted April 7, 2021 looking at the demystification schematic, the p220 has an oil pressure switch that, if i am reading the schematic right, just turns on an idiot light. However, the switch that i have on the replacement motor i am transplanting is meant to be a low pressure cutoff switch, not just an idiot light. Now, I plan on wiring the idiot light to it, as, i feel there is no harm, but, i'm also thinking that i want it to cut the spark if the switch isn't made. based on the physical location of the switch and wiring harness, it would look like the yellow line to the coil would make the most sense - and, i wouldn't expect a significant amount of amperage on that line - since i don't know what the switch is actually rated for. Alternatively, because the transplant has a points system, i could interrupt the negative line to the points? thoughts? Share this post Link to post Share on other sites
Handy Don 10,595 #2 Posted April 7, 2021 Several recent posts/threads on oil pressure sensors and wiring can be found by searching the forum. @onanparts.com noted that oil pressure sensor switches in the ignition circuit are common on non-tractor Onan's and come in several configurations. You'll need to know yours before knowing how to wire it. A switch to the indicator light on a 520 must be closed at low pressure. (The switch closes the circuit to ground, per the diagram I have.) A switch inserted between the ignition switch Run terminal and the coil must be closed at high pressure and must not be grounded. If it were me, I'd confirm the pressure switch's configuration by part number lookup or testing (or both) before getting into rewiring. Share this post Link to post Share on other sites
seuadr 488 #3 Posted April 7, 2021 Good point, I'd forgotten that the switch on the original motor is normally closed. The switch i have matches the low pressure cutoff that he has on his site. I didn't think to check if it was grounded, though. Share this post Link to post Share on other sites
