Onan Generator Starter Solenoid Wiring, Location, Problems

It used to be that the starter and solenoid were two separate parts. But with modern technology leading the way, the parts makers have been able to combine the two and make it easier to fix or replace. It may be a bit cheaper as well.

The starter solenoid seems to be on the opposite end of the generator from the belts. It is located at the top of the unit within easy reach. Of course, different Onan generator models may have different locations and the starter solenoid may not be universal.

To learn more about this topic, just continue to read our article. It explores the subject so you get the best information possible and hopefully be able to do your own maintenance or repair work. Take a few minutes to get this information.

Onan Generator Starter Solenoid Location


Since Cummins/Onan makes so many models the location for its starter solenoid may be different for each model. For the Microlite 4000, this part will be on the back side of the generator in the upper right area.

If the generator is built-in, you will have to remove it to make any repairs to this part. The best thing to do if you are not sure where your starter solenoid is, look it up in your manual. There should be a diagram for all the parts

In most cases, according to the diagrams we saw, the starter solenoid is near the starter. The starter is usually at the back of the generator. You will have to remove the casing to get to it.

Also, make sure you have no power running to the generator as you search for the starter solenoid. Keep yourself protected at all times while you do this type of work.

Onan Generator Starter Solenoid Wiring

The best thing to do here is to place a diagram so you can see what we are talking about. In many cases, the starter solenoid is connected to the relay, the F1 relay as well as the start/stop switch.

That is the uncomplicated design and this is for the Onan Genset 4.0 model. Here is a more complicated wiring diagram and it is for the 6.5 model:


You can contact Onan directly and talk to them about their wiring for the starter solenoid. It seems that the company can be very helpful and should be able to furnish you with the correct information.

We did try to get a parts and operator’s manual but you have to log in to gain access to the information. Or you can go to an Onan dealer and see what they say.

Getting expert help is always the best move to make when you are not sure.

Onan 4000 Generator Starter Solenoid Wiring

Here is a simplified diagram for you. It should be easier to follow and allow you to make the repairs you need to make:


Everything is laid out clearly so you can see each part and where the wires go without too much difficulty. For all wiring diagrams in this article, we only represent them as they are represented to us.

We are not responsible for any false labeling on the part of the people who place these diagrams on the internet. This needs to be made clear so there is no confusion or thoughts that we are misleading you.

If you are not sure about this diagram or any of the others in this article, please contact the company to double-check and make sure you are getting the right one.

No one likes to be fooled and we have seen some websites that have done just that. So contact your local Onan dealer and make sure that what you are getting clearly represents the wiring set-up for your specific generator model.

And as we said, Onan/Cummins makes a lot of different RV generators so these diagrams may not be for your specific model.

What Wires Go Where On a Starter Solenoid?


There are only supposed to be 3 wires that directly connect to the starter solenoid. The first wire is the positive one that connects the solenoid with the battery. The terminal should have a B on it for battery so you do not get confused.

The second wire will be the ignition or starter control wire. This one hooks to the solenoid and connects it to the ignition switch. The terminal on the solenoid should have an S next to it.

This wire is a thing one so you shouldn’t be able to confuse the battery wire with the ignition wire even if they are the same color. The final wire will be the motor wire and it connects to the starter motor.

Now in some cases, you will see a 4th wire attached to the solenoid starter. This is the ground wire and you only usually see it if your generator has a 4-post solenoid.

The wires should route in opposite directions to make sure you do not hook up a wire to the wrong terminal. You can look for the letters to help you do the right type of wiring.

The motor wire should be identified by the M next to it.

How To Test a Generator Starter Solenoid

The following instructions are for just about every model of generator out there. This is basic electronics and Onan has not found a better way to test their solenoid starters.

Step One- you will want to get your tools first. You can use a 12-volt light tester or a multimeter

Step two- Make sure the generator’s battery is fully charged before taking any of the following steps

Step Three- Now you are to disconnect the circuit. You do this by removing the negative battery cable. Take care to not let the end of the cable touch anything metal, etc.

Step four- Next, you need to use a screwdriver and remove the wires from the starter solenoid and carefully remove the wires.

Step five- this is where you turn the generator select switch to ‘on’ then attach the probes to the two solenoid posts. If the light tester does not light up or the multimeter does not register any voltage then the starter solenoid is bad.

That brings us to the next section where you will need to remove the old solenoid and replace it with a new one.

How do You Replace a Starter Solenoid on Onan Generators?


The process will basically be the same for all models of generators. The only difference is if your generator is gas or LP. If the latter you will need to remove the filter before removing the solenoid starter.

If it is a gas model, then you may have to remove the fuel pump before removing the starter. Once you get those parts off, it should be relatively easy to remove the starter solenoid.

Before you start though, make sure to disconnect any power to the generator. The last thing you will want will be an electric shock. Before you get to the bolts holding the solenoid in place, make sure to remove all the wires connected to the part.

Once those are off, you can remove the bolts and the solenoid with ease. Then when you put the new part on just reverse your steps. Make sure to do a test so you do not place a wire on the wrong terminal.

Champion Generator Starter Solenoid

When you have trouble starting your Champion generator, there are 16 possible sources. The last possible source listed is that the starter solenoid has gone bad.

The signs for this part going bad will be that you will hear some clicking noises or a humming sound. The source for this problem would either be the weakening of the internal spring or the copper plate has begun to corrode.

Other possibilities could be a bad battery, a weak starter, or a bad ground. To test to see if the starter solenoid is bad, you just need to bypass this part. You do that by connecting one end of the wire to a battery terminal and the other end to the starter.

Before you replace the solenoid though, you should check the ground and all wires to make sure they are connected correctly. If you can manually start the generator then the source of the problem is in the electric start system.

If you need a replacement Champion starter solenoid, then contact the Champion Help Center for more advice and a new part.

Generac Generator Starter Solenoid


One thing you will notice with all the different brands of generators out there. Their electrical systems are very similar and the troubles are the same. With this brand, you will find that testing the starter solenoid to see if it is bad is the same as the Champion method.

You bypass the solenoid and connect a wire from the battery terminal to the starter. If it starts, then you know the solenoid is bad. Getting a replacement should not be that difficult as many small engine repair shops advertise that they sell a Generac starter solenoid.

It is possible to use a light tester as well as a multimeter if you do not want to see sparks. Sparks are one of the side effects of bypassing the solenoid with the wire. The cost of the solenoid will range in price depending on which model of generator you own.

You may be able to find an after-market starter solenoid that is compatible with the Generac model. That should cut your costs down.

Kohler Generator Starter Solenoid

The company’s website has this to say about its starter solenoids:

Kohler Starters are tested with the most severe validation processes in extreme operating conditions to ensure reliability and performance in any application” (source)

These may be ideal extreme conditions but it is hard to say. Your results may differ once you get out in the back woods and want to use your generator. The company also has a service and parts web page.

If you are having difficulty finding help or the needed part, use the link above to get the help you need. The company also recommends that you use their parts only. They state on another web page that they know what you need when it comes to your Kohler generator.

They also say that other branded parts may look the same and do the same work, they are just not made to be used in a Kohler generator.

Honda Generator Starter Solenoid


While Honda is said to be the most popular and best generator making company, it too will fall prey to a bad starter solenoid. The brand may be different but electrical problems are all the same no matter who makes the generator model.

If you are looking for the location of this brand’s starter solenoid, then like all the other brands, you can call a dealer, look it up in the operator’s or parts manual, or call the company direct.

Then the testing and replacement procedures are all the same as the other brands. If you do not feel comfortable with trying the wire from battery to starter method, get a technician to come out and have him do it for you.

In most cases, when it comes to electrical issues, it is best to let a technician handle the diagnosis and repair.

Some Addition Words

Most generators are basically designed the same. The biggest difference will be found between the many models that each company makes. Also, there will be slight differences between gas and LP units.

Your repair work will depend on the type of generator you own. Make sure you do understand which one you own as that will make it easier to find replacement parts.

When in doubt contact an authorized technician or dealer. That should be your fastest way to get your generator up and running again. Don’t forget to disconnect the power if you do your own work.

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