How to Test a Low-Pressure Switch on AC

An AC usually contains different elements, and the pressure switch is among them. It is meant solely for safety purposes. You will find it on the low and high sides of the AC unit. Its main work is to estimate and control the AC’s refrigerant pressure.

The AC pressure switch comes in two: the low and high. The one found on the lower part of your AC is known as the low-pressure switch, while on the higher side is the high-pressure one.

In this blog, our focus is on the low-pressure switch. We shall learn how to test a low-pressure switch on AC to help you keep your AC running.

But first;

What is the Mandate of the Low-Pressure Switch?

With a low-pressure switch in place, you can rest assured that any faults in your AC’s refrigerant will be dealt with accordingly. It identifies any problems before they can damage the compressor. Low pressure means that the compressor is in peril because it operates on low refrigerant.

Generally, the low AC pressure switch turns off the entire air conditioning unit to save the compressor in this scenario. If the low-pressure switch is bad, it could cause the compressor to overheat and fail.

So, if your AC isn’t blowing cold air, it’s important to test this switch and see if it needs to be replaced.

Difference Between a Low and High-Pressure Switch

Most people use both of them interchangeably. They are both in charge of managing the AC pressure and preventing the compressor from any damage. However, there is a difference in functionality between the two.

High-Pressure switches are designed to protect your AC unit from high pressures. These switches will shut off the AC unit if the pressure gets too high.

Low-pressure switches, on the other hand, are designed to protect your AC unit from low pressures. The switch will shut off the AC unit if the pressure gets too low. Most AC units have both a high-pressure switch and a low-pressure switch, but some only have one or the other.

The pressure from the low-pressure switch should be between 90 and 110 psi. If the pressure is outside of this range, it could mean that the switch is bad and needs to be replaced.

On the other hand, the pressure on the high-pressure switch should be between 250 and 350 psi. Anything outside this range should prompt you to replace the switch.

How to Test Low-Pressure Switch on AC: Best Steps

The following are the ideal steps on how to test AC low-pressure switch;

Step 1: Get the Right Assembling the Tools

Most of the tools used to test an AC low-pressure switch are pretty standard. They include;

5/16″ nut driver1/4″ nut driver, Screw driver, Multimeter

Among the four tools, the multimeter is a must-have. Moreover, knowing how to use it will be a plus for you when testing the AC low-pressure switch.

Step 2: Locating your AC Unit’s Low-Pressure Switch

The second thing to do is to locate where the low-pressure switch is. You will achieve this by opening the furnace using the right nut driver or screwdriver.

This switch is usually located near the compressor, on the suction line. Once you’ve found it, you’ll need to test it to see if it needs to be replaced.

Step 3: Use Ohms to Diagnose the Low-Pressure Switch

At the service switch, detach the power. Position the multimeter to Ohms, indicated by a Greek omega sign. Ensure that you disassemble the two wires on the low-pressure switch and seal them. Switch on the power at the service switch again.

The combustion process will now occur (the draft inducer will help you know this). Place the two leads from the multimeter at the two terminals. Ensure that the switch is in contact with no resistance whatsoever.

In most instances, the multimeter will beep. If it does, it means that the switch is all good. The opposite is also true when it does not beep – it means you might need to replace the switch.

Reattach the wires that you had earlier disconnected if the switch is okay. The process of testing your AC low-pressure switch is as simple as this.

How Do you know your AC Low-Pressure Switch is Bad?

There are several ways to tell if your AC low-pressure switch is bad. One way is to check the pressure on the switch. If the pressure is outside of the ideal range, it could mean that the switch is bad and needs to be replaced.

Other common signs of a faulty low-pressure switch include;

 A Faulty Compressor

The compressor’s task is to ensure that the refrigerant flows via the AC unit. In turn, it causes the AC to cool down your indoor air.

A faulty low-pressure switch will lead to a damaged compressor, as the system can’t control the pressure. So, if your AC is not blowing cool air to your space, you might want to check out that switch.

AC Unit Keeps Turning On and Off

If your unit keeps turning on and off, there is a significant possibility of a problem with the AC low-pressure switch. In case it behaves this way, testing it to determine if it’s working properly is the best thing.

Loud and Strange Noises

If you hear some funny noises coming from your AC, there is cause for alarm. It might be an indication of a faulty low-pressure switch that requires some quick fixing. Otherwise, with a normal functioning low-pressure switch, the unit produces minimal or no noise at all.

If you go through the testing steps and can’t figure out the exact problem with the unit, calling for help is recommended. Seeking the help of a professional is the next best step to ensure that your AC’s problems are sorted once and for all.

At Direct Air, we pride ourselves on a team of professionals who will work tirelessly to ensure your home is as comfortable as possible. Therefore, don’t hesitate to reach out and learn how to test a low-pressure switch on AC.

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