Click! Did your air conditioner’s high pressure switch just trip?
A tripped high pressure switch makes a loud click followed by an abrupt shutdown of your AC condensing unit.
But what causes a high pressure switch to trip? And how do you prevent your AC’s high pressure switch from tripping?
In this article, I’ll go over what you should do if your AC’s high pressure switch trips. I’ll also cover the causes of a tripping high pressure switch, and some maintenance tasks that you can perform to keep your AC’s high pressure switch from tripping in the first place.
What to Do When Your AC High Pressure Switch Is Tripping
A tripping high pressure switch is almost always caused by insufficient heat rejection.
That’s why the first thing that you should look at is your AC’s heat rejection devices – the condenser coil and condenser fan.
Here’s what you should do if your AC’s high pressure switch is tripping:
Clean the Condenser Coil
The first thing that you should do if your AC high pressure switch is tripping is clean its condenser coil.
The condenser coil is located in your AC condensing unit outside – so it gets dirty under normal operation.
If the condenser coil gets excessively dirty, the high pressure switch may trip since the condenser coil can’t reject heat quickly enough.
I recommend spraying out the condenser coil with a garden hose to clean it.
If the coil is clogged up, then using an AC coil cleaner will help dislodge the debris from the coil.
Whatever you do, don’t use a pressure washer to clean your condenser coil. Using a pressure washer is not necessary and will cause damage to the condenser coil fins.
Check the Condenser Fan
The condenser fan generates airflow through the condenser coil. If the condenser fan doesn’t spin, then the condenser coil won’t reject heat properly and your AC high pressure switch will trip.
Check the condenser fan to make sure that it spins when the condensing unit kicks on. Make sure that the fan isn’t making excessive noise or wobbling since that indicates an issue with the condenser fan.
If the condenser fan doesn’t spin at all, there could be a malfunction with the fan motor or capacitor – which I’ll go over below.
Test the Condenser Fan Motor Capacitor
The condenser fan motor capacitor is required for the condenser fan to start up and run. If the fan motor capacitor goes bad, the condenser fan won’t start and your AC high pressure switch will trip.
If your condenser fan isn’t spinning, you should do is test your AC condenser fan motor capacitor with a multimeter to see if it’s bad.
A bad condenser fan capacitor will need to be replaced.
Causes of a Tripping AC High Pressure Switch
High refrigerant pressure in your AC condensing unit is the main cause of a tripping AC high pressure switch.
But what causes high refrigerant pressure in your AC?
The most obvious cause of high refrigerant pressure is a high refrigerant charge – but that’s actually quite rare since the only way for a high refrigerant charge to occur is if someone charges up the AC too much.
And if your AC was running just fine for a while, it’s not going to suddenly get a higher refrigerant charge.
In most cases, the cause of a tripping high pressure switch is due to insufficient heat rejection.
The condenser coil is the main heat rejection device in your AC, and the condenser fan is responsible for aiding in heat rejection. So issues with the condenser coil or condenser fan are usually what causes a high pressure switch to trip.
Here are the causes of a tripping AC high pressure switch:
Dirty Condenser Coil
A dirty condenser coil is one of the most common causes of a tripping high pressure switch in an AC.
If your AC condenser coil gets too dirty, then it can’t reject heat and the refrigerant pressure will get too high and trip the high pressure switch.
Bad Condenser Fan Motor Capacitor
If your AC condenser fan motor capacitor goes bad, then your condenser fan motor won’t spin and reject heat from the condenser coil.
So if you hear your AC compressor running but the condenser fan isn’t spinning, the first thing you should check is the condenser fan motor capacitor.
To test your AC capacitor, you’ll need to shut off power to your AC unit and discharge the capacitor, then use a multimeter to test the capacitor.
Bad Condenser Fan Motor
If your AC capacitor is good but the fan motor still doesn’t turn on, the condenser fan motor is bad.
Condenser fan motors go bad due to a variety of reasons – usually due to airflow obstructions or motor burnouts.
If you suspect that your AC condenser fan motor is bad, you should test the motor and replace it if necessary.
High Refrigerant Charge
A high refrigerant charge will cause your AC to run at higher pressures than normal.
However, a high refrigerant charge isn’t something that just happens overnight – it only happens when the unit is overcharged with refrigerant.
So if your AC’s high pressure switch trips when it has been otherwise running normally, then it’s probably not due to high refrigerant charge.
But if your AC’s high pressure switch trips right after an AC technician worked on it, the trip could be due to a high refrigerant charge.
High Heat Load in Your Home
If the inside of your home is extremely hot, your AC high pressure switch might trip due to a high heat load.
A high heat load will make your AC unit run with high refrigerant pressures. If the high heat load situation persists, then the high pressure switch might eventually trip due to the excess heat.
A high heat load situation is rare, and it’s not likely to cause many high pressure switch trips. But I thought that I’d mention it here since it does happen from time to time.
High Ambient Temperature Outside
If it’s an excessively hot day outside, then your AC high pressure switch might trip as your AC unit struggles to reject heat.
Heat exchange is directly affected by the temperature difference between the condenser coil and the ambient air temperature.
So if the temperature outside is higher than normal, then your AC will have to work harder to transfer heat from its condenser coil to the air outside your home.
How to Prevent Your AC High Pressure Switch From Tripping
Preventing your AC’s high pressure switch from tripping is all about ensuring that your AC can reject heat properly.
So the main things that you should take care of are your condenser coil and condenser fan.
Here’s what you should do to help prevent your AC high pressure switch from tripping:
Keep the Condenser Coil Clean
Keeping your AC unit’s condenser coil clean is the most worthwhile thing that you can do to prevent its high pressure switch from tripping.
A clean condenser coil will reject heat quickly and efficiently and will keep the refrigerant pressures in your AC system within normal range.
Provide a Clear Path for Airflow Around Your Condenser Unit
If your AC condenser unit is starved of airflow, then the high pressure switch will trip.
Keep all objects away from your condenser unit, and never put anything on top of your condenser unit.
Also, keep plants trimmed back away from your condenser unit.
Avoid Short Cycling Your AC Unit
Short cycling happens when your AC unit repeatedly turns on and off within the span of a few minutes.
A normal cooling cycle is around 10-15 minutes. If your AC is turning on for a shorter period of time, such as only 3-5 minutes, then it is short cycling.
Short cycling is bad for many reasons, one of which is that it will cause your AC high pressure switch to trip under certain circumstances.
Most AC thermostats have anti-short cycling parameters in their settings to prevent short cycling.
If you notice that your AC is short cycling, then go through the settings on your thermostat and adjust them to prevent short cycling.