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Constant Duty Solenoid: How Does It Work?

Different types of solenoids exist, such as a constant-duty solenoids, starter solenoids, regular solenoids, and continuous solenoids. So, what is a solenoid?

A solenoid is a cylindrical device with a tight metal coiling whose role is to convert electrical energy and change it to mechanical power.

The focus of this article is on the constant duty solenoid. How and where do they find heavy usage?

What’s the difference between a continuous-duty solenoid and a regular solenoid? Do you want to learn more? Keep reading. 

Table of Contents

What is a Continuous Duty Solenoid?

The traditional or regular starter solenoid you see daily sends power to your engine’s starter when you turn the ignition on to the start position.

Solenoids work by closing the circuit, immediately sending power from the starter to the engine.

And the moment the engine runs independently, the solenoid will open the circuit, cutting off power emanating from the starter. 

With a continuous duty solenoid, the working principle is also similar. A continuous-duty solenoid opens and closes a circuit to control power flow.

However, it would be best to remember that the power flow to a continuous duty solenoid is slightly different, remaining near-distant distance instead of short bursts. 

In a continuous-duty solenoid, the power level is slightly lower than what goes through the starter solenoid.

However, this is to accommodate or effectively function for a longer duration of work. 

What constitutes a solenoid

(What constitutes a solenoid)

Application of Continuous Duty Solenoid

So, where would you find heavy usage of continuous-duty solenoids? Now that you understand how continuous duty solenoids work, you must wonder where they find their use.

In short, a continuous-duty solenoid is necessary when you need constant power, especially in mechanical operations.

The ability of continuous-duty solenoids to function at cooler temperatures means that they will not easily burn out as they continue undergoing repeated workloads.

This is why many find continuous-duty solenoids ideal for most of their operations. 

You may need a continuous-duty solenoid, especially if your starter battery cannot power a battery in a recreational vehicle or van.

Such would allow these solenoids to operate at low levels while charging when the power switch is on, a big advantage of continuous-duty solenoids. 

Continuous duty solenoid at work

(Continuous duty solenoid at work)  

Continuous Duty Solenoids vs. Regular Solenoids

As briefly mentioned, how a continuous duty solenoid works is almost the same as how the regular starter solenoid operates, opening and sealing the circuit to ensure the power flow turns off and on.

The only slight difference is that the power flow remains mostly constant in the continuous-duty solenoid.

In a regular solenoid, the power flow is intermittent. 

Again, the power that travels through a continuous duty solenoid tends to be much lower since it has to run for a long.

If you’re keen enough, you’ll notice that, generally, continuous-duty solenoids don’t power any system that could be as hot as your car’s vehicle system.

Most are designed to tolerate low levels compared to regular/starter solenoids. 

Regular starter solenoid on a white background

(Regular starter solenoid on a white background)

Working principle of the Regular Solenoid

A century back, for individuals to start their car engines, they had to crank them manually.

For the sake of convenience, engineers needed a way to avoid such.

The starting mechanism had to effectively drive the engines fast and generate power to be effective.

This was a huge undertaking since it required a lot of power. 

Without the current ignition system alongside the regular solenoid, thick cables had to transmit power from the battery to the ignition and then from the ignition to the starter.

However, the regular solenoid and the ignition system make it easy to run a single cable only, from the power to the solenoid, with the solenoid acting effectively as a dam, preventing the power through until there’s a turn of the ignition. 

As you turn the ignition to the start position, the regular solenoid will close the circuit, sending the power to the starter, which then turns the engine.

When the engine runs under its power independently, you can release the key, returning the ignition to the “on” position.

The regular solenoid will then open the circuit, cutting the power to the starter. 

Regular solenoid at work

(Regular solenoid at work)

Why are they not interchangeable?

Starter solenoids and continuous-duty solenoids are not interchangeable since they each have to meet the needs of separate systems.

They are different in their function, and interchanging them would be dangerous.

If you aren’t aware, the continuous duty solenoid can’t effectively withstand the power needed in a machine’s starting system.

A starter solenoid cannot withstand the heat of running constantly. 

If you go ahead and use the wrong solenoid, you may make it burn out within a very short period, requiring you to make regular repairs.

If you want to minimize repairs, save your hard-earned funds, and ensure that your fleet of vehicles last long at all times, make sure you use the right solenoid for your application. 

starter solenoid

(starter solenoid)


Solenoids are crucial in converting electrical energy to mechanical power, especially in motor vehicles.

Different types of solenoids exist, all serving their purposes.

If you have a car or a fleet of vehicles, to ensure that you get the most out of them, among other things, make sure that you use the right solenoids. 

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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