How to test a pressure switch with a Multimeter

How to Test a Pressure Switch with a Multimeter?

Pressure switches are an important part of the functioning of a system, even though they technically aren’t part of the system. Pressure switches keep your equipment working and safe, and a broken pressure switch will cause problems right away.

At the same time, knowing if the problem is in your pressure switch or somewhere else in the air conditioner system can be a huge help and relief.

Although replacing a pressure switch is quite a technical job, testing a pressure switch and pinpointing the real problems with your air conditioner is something you can easily do yourself with a multimeter. 

In the article below, we will discuss some common problems you may run into, and the exact steps you need to test a pressure switch.

What is a pressure switch?

A pressure switch is a small device that you can find around equipment at homes, in cars, vending machines, and industrial manufacturing plants. It is used to control equipment like industrial welding machines, but also your heating and ventilation system at home.

The simplest form of a pressure switch indicates when a system has reached a defined pressure. As the name already suggests, a pressure switch has a pressure meter and a switch component.

When a certain pressure is reached, the switch will activate and pause or stop the electrical circuit that the pressure switch is a part of.

pressure switch

Common Problems with Pressure Switches

There are several problems that can arise with pressure switches. We’ll try to cover the most common ones, so you’re better equipped to deal with pressure switch problems and its testing methods.

Although there are different types of pressure switches, they all work the same in principle, and testing them with your digital multimeter will look the same.

One common problem with pressure switches is that some of them have diaphragms that tend to break over time. Another type of damage that is common in multimeters is normal wear and tear, which leads to cracks and broken components.

Because most people will deal with pressure switches in their air conditioner systems, a common problem that comes from a bad pressure switch is when your air conditioner is frequently cutting off, tries to start again, or doesn’t work at all.

When this happens regularly, checking your pressure switch could be an easy way to find the problem in your air conditioner in your car or at home.

How to find the pressure switch in your A/C system

The best way to find the pressure switch in your air conditioner is by consulting the manual for your car or in-home air conditioning system. Locate the A/C, and find the pressure switch attached to it.

In most models, you will be able to remove the switch separately from the A/C itself, so you don’t have to take out the whole A/C.

Find out more about A/C pressure switches in this video:

How to Test a pressure switch with a multimeter

Now, let’s find out how to test a pressure switch with a multimeter. At the core, a pressure switch is the same as any other switch.

This means that once the component (a pressure switch in this case) is disconnected from the main body (the A/C unit in this case), you can test the pressure switch as you would any switch.

Put the multimeter in the Ohms position (usually displayed with the Ω symbol). Make sure you’re measuring single ohms, and not mega-ohms. Double check that your leads are in the right place to test for Ohms, and get the switch.

When you turn the pressure switch around, you’ll notice a side with different terminals. If you don’t see any terminals, there is a chance you need to remove the cover first.

If you have found the terminals, get your leads and touch one on each terminal. A closed switch should read 0 Ohms. If you see ‘infinity’, you’re indeed working with a faulty switch.

How to Test with a Special Accessory

Some multimeters offer special accessories that help you with specific problems. One of these accessories will help you with testing a pressure switch. The best known accessory is the Fluke pressure gauge.

This accessory makes testing a lot easier but is usually reserved for the professional. If you’re lucky enough to have one on hand, however, you can easily test and calibrate your pressure switches by adding a hand pump with the special pressure gauge accessory to the end of the pressure switch.

The first part of the testing process stays the same. Put one of your leads on the common terminal, and the other on the normally open terminal. This gives you the initial test results.

For more results, apply pressure with the hand pump and read the pressure gauge to get a better idea of what to fix or improve about the pressure switch.


Pressure switches can be tricky. You’ll know once they’re broken, as they will cause the whole air conditioner system to act out. At the same time, testing the pressure switch is an easy way to eliminate more elaborate problems with your air conditioner.

Knowing how to test a pressure switch with a multimeter might save you precious time and money, as it can pinpoint the problem pretty fast.

Remember that actually fixing a pressure switch can be very tricky. Most of the time, it is easier, cheaper and faster to just replace a faulty pressure switch. You can search for your specific pressure switch online or call your manufacturer to order a new pressure switch.

If you’re looking to find a multimeter to test your pressure switch (or anything else), the reviews on our website are a great place to start looking. We have reviewed multimeters in a wide range of price categories and specialties, so you will be sure to make an informed decision on which multimeter to choose.

When it comes to testing pressure switches, you’ll have a hard time finding a multimeter that won’t perform a pressure switch test. By the way, I’d suggest to take a look at Fluke 87V which you can buy on It’s a great multimeter.

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