Difference Between Starter Relay and Solenoid

A lot of people think that a starter relay is the same as a solenoid. If you are not a mechanic and don’t own a winch, this is probably a harmless supposition. But for offroad-loving winch owners, this can be a damaging mistake. The winch has many important parts that make the winch useless is one of these parts is damaged.

A lot of times, your winch can be damaged while traversing off-road. You may have to do repairs on your winch (hopefully this doesn’t happen to you, here’s how to protect yourself when on the offroad). At times like this, it is very important to make sure you make no mistakes, no assumptions, and no unfounded guesses.

So let’s get educated on what are the differences between a starter relay and a solenoid.

What is the Starter Relay?

First thing you need to know regarding the starter relay on your winch: your winch does not have a starter relay.

This might come as a shock to you. That’s because the words “starter relay” is often interchangeably used for the word “solenoid”. A lot of people, and even websites, say that they are the same thing. This is why it can get confusing.

A starter relay is part of a vehicle’s starting system. Also part of that system is the solenoid. This is why it can get confusing as to which part is which. Incidentally, the two parts also have a similarity in appearance. But they’re functions are different.

What Does the Starter Relay Do?

Although just a small electrical device found in the bigger starting circuit of a vehicle, the relay delivers a powerful current to the vehicle motor. This function is very similar to the winch solenoid – hence the confusion. But the difference is, the starter relay is merely a switch while the winch solenoid is both a relay and an actuator.

Aside from cars, a starter relay is also used as a remote switch that controls the circuits with a high current. Such applications include refrigerators, motorbikes, lawnmowers, and more. One of the things that don’t need a starter relay is a winch. And that is the core difference between the two.

Differences Between a Starter Relay and a Solenoid

Here are the main difference between a starter relay and a solenoid. Keep in mind that the solenoid discussed here pertains to the solenoid found in the starting circuit of a vehicle. As was already explained, a winch has no starter relay. So you can’t be confused whether its solenoid is a relay.

As for further discussing the starter relay and solenoid on a vehicle, let’s just do it for learning’s sake. The more you know, the better equipped you are at taking care of your vehicle.


The first difference one can notice about these two machines when placed next to each other is their sizes.

The starter relay is significantly smaller than the more heavy-duty solenoid. This is true whether the solenoid is from a winch or a car’s starter solenoid.


The solenoid’s internal construction is composed of two coils of wire (similar to Tesla’s coils) and amagnetic core on one end. This core moves in and out when the solenoid is activated.

When the starter relay is activated, a current flows through the coil winding. This produces an electromagnetic field. This electromagnetic field moves one of its visible plunger or armature to close the circuit, thus switching on the motor.

On a solenoid, however, it is the core that moves when the electromagnetic field is created. This movement does two things: closes the circuit and moves a gear to function as an actuator.


The function of the solenoid in a vehicle’s starting system is to activate the motor and get it working. This is why the solenoid is usually near the motor housing. A lot of times, the starter solenoid is found right beside or on top of the motor.

As for the starter relay, it’s placement depends on the type or model of the car. It can be in the power or fuse box; under the dash, within in the fuse panel; or it can be in the right fender. Of course, you might also find it under the hood. The relay is often installed on the driver’s side of the vehicle.

But again, the location of the relay may not even be in any of the places mentioned above. If that’s the case for you, consult the manual of your car.

Does a Winch Need a Starter Relay?

When installing a new winch, a lot of people tend to connect it to the starter relay thinking that the winch motor is essentially a repurposed starter motor. This is unnecessary.

The winch doesn’t need a connection to a starter relay. When installing a winch, you should directly connect it to the battery of your car.

The solenoid is enough to control the current that flows into your winch motor. If you need help bench testing your entire winch to see if there are problems, see this step-by-step guide.

Last Word

Again, a winch does not have a starter relay. When telling your winch repair provider, don’t confuse them by saying that your starter relay is broken.

The starter relay is part of a vehicle’s, or other machines that need circuits with high currents, starting system. It functions as a switch for the motor whereas the solenoid functions as both a switch and an actuator.

If you need help installing a new winch, if you don’t know which parts go where, here is a basics guide.