How To Test A Tractor Starter Solenoid

July 30, 2021

Inspecting the tractor starter solenoid components.

Tractors, of course, are somewhat similar to cars when it comes to their starting components. They more often use an electrical starting system. If this electrical starting system fails, the tractor will surely not start. 

The tractor starter solenoid features a cylindrical design, and its primary purpose is to complete the connection loop between the low-amperage battery and the high-amperage motor. The solenoid works like a low-amperage relay. If the solenoid is not working well, the transfer of electrical signals gets denied. With no electricity flow into the tractor’s motor, the motor will not start.

Steps on Testing Your Tractor Starter Solenoid

If you have a tractor—equipped with an electrical starting system—it will have a starter solenoid component. If that is the cause of the starting problem, you should know how to test its functionality. To test it, you will need some hand tools and a working knowledge of how the solenoid functions in the electrical starting system. 

As mentioned above, the solenoid is a low-amperage relay. It does function to connect the loop or connection of the high-amperage motor. This engagement occurs somewhere between the tractor’s battery and the starter motor. Moreover, the ignition key initiates the connection process. 

If the solenoid doesn’t work well, the transfer of electrical signals gets denied. Without the needed electrical flow, the motor won’t start or turn on. You will need hand tools like multiple wrenches, sandpaper, battery charger, jumper cable, screwdriver, and a workable voltmeter to accomplish the testing of the solenoid starter. Here’s a simple rundown of the steps you must follow to test your starter solenoid:

Step 1: Check the Charge Level

To check the charge level, you can use the voltmeter and nudge the battery’s positive post using the voltmeter’s red lead. Then, connect to the negative post the black lead. The voltmeter will indicate the charge level of the battery. If the reading is just below 12.5 volts, you need to charge it.

Step 2: Inspect the Electrical Connections

If you notice that the battery’s voltage is working fine, you need to inspect the connections between the different components. It is likely that the connection somewhere between the starter and solenoid or the battery is loose. 

Another factor is corrosion. Corrosion, over time, can eat away on the different connections and components, causing impedance and reducing the effectiveness of these components. 

You can also check the solenoid if it is attached to the tractor’s frame and stays near the starter motor. In between the solenoid and starter motor, you will see black wires. One of these black wires originates from the starter motor. Others, however, connect to the battery. 

Another thin wire, on the other hand, originates from the ignition key. The ignition key sets the solenoid to active mode when you start the tractor. You will also notice a small wire that is the grounding wire. Ensure to inspect all these small wires. 

You will not have any hard time locating the battery connection. Besides, you will see the starter motor—a cylindrical metal piece that is vertical in appearance. It should stay mounted onto the engine’s side about six inches long. 

Step 3: Remove the Corrosion

You will notice that there will be a buildup of corrosion in some components of the starting kit. You can get rid of this corrosion. Nevertheless, if the corrosion is large enough and is stubborn, you need extra effort to get rid of it. You can use medium-grit sandpaper to work on the corrosion without damaging the components affected. 

Keep on sanding until you make the area affected by corrosion rust-free. Afterward, you can connect the wires. Ensure that there is no loose connection. 

When done sanding, you can set the gear to neutral and set the tractor to disengagement mode. Set, as well, the parking brake and reconnect the battery. You can now let the engine start to figure out if everything is working well.

Step 4: Replacement Testing

If you find that the corrosion is not the source of the starting issue, then go on testing. Turn the ignition key. Then check the solenoid’s terminal posts. These terminal posts consist of thick red wires connected to the solenoid. Touch these huge terminals with the shaft of the screwdriver. If the engine starts, the problem is with the solenoid. It may be damaged completely. So, it is necessary to replace it. 

If the engine doesn’t engage during startup, then it may be a defective motor. Find the huge terminals on the other side of the solenoid and use a jumper cable to connect them. If your tractor comes with an engine model equipped with an integrated motor and solenoid setup, then I am afraid it is not replaceable separately.

Symptoms Indicative of a Defective Starter Solenoid

If nothing happens after engaging the ignition, then it may be with the solenoid. The starter solenoid may be damaged. If the starter is engaging but does not disengage with the release of the key, then it is likely that the solenoid is seriously damaged. Such damage may spread and affect other parts. 

Another symptom that is indicative of a damaged solenoid is when the tractor occasionally starts. In such a case, prepare yourself for solenoid replacement. 

On the other hand, if a solo click emanates from the engine’s compartment, it indicates that the solenoid tries to start the tractor’s engine but is hampered by some internal components. 

Lastly, if the tractor’s engine appears to start itself on its own, the solenoid may be seriously damaged and needs prompt attention.


The solenoid is a crucial component of the starting system. If it is defective or is no longer working, you will indeed have a hard time starting up your tractor. The abovementioned facts and ideas can help you check on the present status of the solenoid. Of course, if you are not a mechanical type of person, you might as well avail of the service of a professional mechanic to check on the source of this starting-up problem. Thus, you can assure yourself that everything will be working well afterward. 

Periodic maintenance or testing of your tractor will surely come a long way in keeping your tractor in top-notch condition. Moreover, it can help you prevent the onset of major mechanical issues by promptly addressing the minor issues that may balloon into a major problem in the near future.