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Rich Biebel · 10-13-2014, 06:50 PM

Did you install a pressure gauge in place of the switch to verify the pressure is good?

Oil weight should really not be an issue here but the pressure needs to be confirmed as good with a mechanical gauge.

The proper switch is a must......but if the pressure is low it may be your problem.

Obviously lower weight oil will have an effect on pressure as will temperature. I seriously doubt the issue is the oil your using.

The parts manual shows a single terminal switch and it is mounted in a 90 degree fitting.

Part number is 309-0319 and is also shown in the price guide as a good number and list price is $12....

Yes your machine has a run relay and a resistor that is part of this circuit. The oil pressure switch closes to ground when pressure builds up. 30lbs is the proper minimum pressure.

I cannot cut and past the page on testing this control circuity for you from the Servcice Manual and don't have a paper copy to be able to print out...Those old machines used a lot of old type circuitry....and once you verify the pressure is good you can move on to the wiring and find the relay and resistor....

If it is one wire it can only do one thing.....close the wire to ground and open it to ground. That generally means it controls something else......a relay.....since it cannot directly supply the 12+ needed for the coil......

10-13-2014, 06:50 PM	#18
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,320 Likes: 25 Liked 557 Times in 217 Posts	Re: Onan Aux Issue Did you install a pressure gauge in place of the switch to verify the pressure is good? Oil weight should really not be an issue here but the pressure needs to be confirmed as good with a mechanical gauge. The proper switch is a must......but if the pressure is low it may be your problem. Obviously lower weight oil will have an effect on pressure as will temperature. I seriously doubt the issue is the oil your using. The parts manual shows a single terminal switch and it is mounted in a 90 degree fitting. Part number is 309-0319 and is also shown in the price guide as a good number and list price is $12.... Yes your machine has a run relay and a resistor that is part of this circuit. The oil pressure switch closes to ground when pressure builds up. 30lbs is the proper minimum pressure. I cannot cut and past the page on testing this control circuity for you from the Servcice Manual and don't have a paper copy to be able to print out...Those old machines used a lot of old type circuitry....and once you verify the pressure is good you can move on to the wiring and find the relay and resistor.... If it is one wire it can only do one thing.....close the wire to ground and open it to ground. That generally means it controls something else......a relay.....since it cannot directly supply the 12+ needed for the coil...... __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 10-13-2014 at 07:15 PM.