And here it is, proven to work now.    Wells #PS-122   http://www.wellsve.com/showall_ds_oil.php   that NLA Toro oil pressure switch for the Onan engine? Or the Onan part that’s $159.00? Scratch that. This piece here ^^^ I bought at my local O’Riellys for $5.73.    Yes, it’s a three terminal switch, not two like the factor, but... it works. Terminals 1 and 3 are tied together and work when oil pressure is applied. They disconnect when there is no pressure. Terminal 2 grounds when there is no pressure and disconnects when there is pressure. You have to wire a new ground wire from either terminal 1 or 3 and find a suitable ground for that, and then connect the black wire from the - of your hour meter to the either terminal 1 or 3, whichever you didn’t already use. Terminal 2 gets connected to your idiot light for the “no pressure” indicator.    I can tell you that it all works as it should. Idiot light works and goes off when running and now my hour meter functions too. Very happy!