Now I feel stupid Onan doesnt turn over

Use the serial number of your tractor to see if we have the correct OP Manual for your tractor. That has a proper wiring diagram that identifies the colours of the wires. If we don't have that manual, then find the Parts Manual. It will have a wiring PICTORIAL that is almost as good.


Here's what you need to understand. The key switch sends 12 volts to the solenoid to get it to close so that the heavy current from the battery will cause the starter to spin. Sometimes, the safety switches interrupt the 12 volts that the key switch is trying to send to the solenoid. You need to buy a simple tester to figure out which switch is not closing. The tester looks like a screwdriver with a sharp end on it. The handle is clear because there is a lamp inside that lights up when 12 volts are present. There is also a wire that exits the top of this tester with an alligator clip on the end. You clamp that end onto a good ground such as the negative post of the battery and then use the end of the tester to look for 12 volts while someone holds the key to the start position.

The wiring diagram will show you the colour of the wires that are in question. You have to use the tester on the ignition switch first. Turn the key several times to the START position to see if 12 volts shows up on the tester every time. Maybe you have a bad ignition switch. If it tests OK, then follow the wire to the whichever safety switch it goes to and keep on testing. Something is intermittently stopping the flow of juice to the solenoid. Only you can perform the tests to figure this out.

The solenoid generally has two wires, yellow and black, that are attached to the small terminals. The yellow one comes from the key switch and sends 12 volts when the key is in the start position while the black is a ground that runs through a series of safety switches. I find the quickest and easiest way to test the solenoid is to place a jumper wire directly between the battery negative post and the solenoid where the black wire is attached then use another jumper from the positive side of the battery to the post with the yellow wire--if the engine turns over then the solenoid is fine. Then do the same test with just the ground jumper and using the key switch and that will tell you if your switch/wire is ok. If all these items test out ok then your problem is in the ground wire on the solenoid and you will need to trace it for continuity through the safety switches--your problem could be damage to the wire or a bad switch or, perhaps, you just don't have the travel control precisely in neutral. By following the black wire you should be able to isolate the problem.

I don't know if my advice and Bart's advice is confusing you. Essentially, both of us are right.

Here's why. I don't know what tractor you have. All you disclosed in this thread is that it is Onan powered but you did indicate that you had a solenoid mounted on the starter motor. Or....at least that was my understanding. My reply was based on the solenoid being on the starter motor. Safety switches interrupt the power going to the solenoid.


Now, if your starter motor does not have a solenoid mounted on it, then Bart's advice is correct. The safety switches are used to between ground and the grounding terminal of the completely separate solenoid. This is why using YOUR tractor's serial number to find the correct Op Manual and Parts Manual is so important. This is not a "one size fits all" situation. Different tractors used different engines and they were wired differently. I see this type of confusion all the time on other forums because the left hand does not know what the right hand is doing. People ASS U ME facts not in evidence and then the threads become filled with bad advice that helps no one. This is why this site went to the trouble of creating the Tech Library. When asking questions about your tractor, it is most helpful to include the model and serial number so that everyone knows what you are working on. Do not expect us to keep a log of who owns what. We cannot do that, especially when members own multiple tractors and buy/sell on a frequent basis.