How to Jump 2 Wire AC Pressure Switch

By the end of this article, you should be able to jump a 2 wire pressure switch quickly and easily.

The AC pressure switch is a delicate component that might get expensive if it starts to malfunction. When it does you need to know how to jump it or you’ll have to spend extensively for repairs.

In general, if you have an old two-pin switch, remove the connection and bridge the wire across the connector’s pins to jump an AC pressure switch. You can temporarily jump a low-pressure switch in a car to activate the AC compressor clutch for testing purposes ONLY.

Below we’ll go into more detail on the full process.

How to Jump 2 Wire AC Pressure Switch

Jumping a low-pressure switch is done to test the circuit. What is the purpose of the low-pressure switch? The engine’s air conditioning pressure switch blocks the relay from supplying power to the air conditioning compressor. One thing to keep in mind is never to jump the low-pressure switch while the engine is ON. If this step is done, you may damage the compressor.

Step 1: Start the motor and set the settings to maximum to jump a low-pressure switch. 

Step 2: Unplug the cycling switch connector, then connect the two female ports to the unplug connector.

Step 3: Check the compressor to verify if it is operational.

There is Just One Reason to Trigger a Low-Pressure Switch

The compressor is turned off using the low-pressure switch to prevent compressor damage from oil starvation. Low refrigerant charge equals no oil circulation. In other words, you can temporarily jump a low-pressure switch in a car to activate the AC compressor clutch for testing reasons ONLY.

However, if you keep it attached for too long in an attempt to recharge the system, you risk significant, even severe, compressor damage. Its AC low-pressure cutoff switch can harm your compressor, sending debris throughout your AC system. Repairing this might cost you a lot of money. Think twice before jumping a low-pressure switch to add refrigerant to your car’s air conditioner. That is not the way to go!

Air Conditioning Compressors Can’t Compress Liquids

Heat causes the refrigerant to boil and transform from a liquid to a gas. It travels through the evaporator in your dash.

The gas exits the evaporator and either enters an accumulator in an orifice tube system or straight into the compressor. It could also be in an expansion valve system, depending on the kind of system in your automobile.

Despite the presence of an accumulator, a tiny quantity of liquid reaches the compressor.

It must be done precisely so that the liquid refrigerant may convey lubricating oil into the compressor. The problem arises when you jump a low-pressure switch for more than a few seconds because you run the compressor without oil. That will destroy it.

When the Air Conditioning Compressor Clutch Does Not Engage, How Do You Add Refrigerant?

When you switch off a car’s air conditioning system, the pressure differential between the high and low sides eventually equalizes.

If the compressor is not functioning, how can the pressure equalize? Simple. As the automobile heats up, the orifice tube or expansion valve continues to flow liquid into the evaporator. That liquid condenses into a gas and goes into the compressor before exiting through whatever compressor reed valves are open at the time.

When the compressor is turned off, there is always a gap between the high and low sides.

As a result, you may add refrigerant to a system even if the compressor clutch is not engaged.

It will simply take a lot longer. Warm the refrigerant can in a basin of warm water to expedite the procedure. It will cause the liquid to boil and raise the pressure. Once the water has cooled, replace it with more warm water. Repeat this method until the pressure gauge on your recharge kit reads more than 25 psi. The low-pressure switch should then allow the AC compressor to activate. (1, 2)

Is It Possible to Bypass AC High-Pressure Switches?

Yes, doing so is possible.

But first, why you’re doing it? Please ensure that you temporarily bypass the correct issue before repairing it. After bypassing the AC high-pressure switch, problems may emerge, which may be caused by damage to the operating condenser fan engine.

So, how can you get around the air conditioner’s high-pressure switches? 

1. Locate the air conditioning pressure switch and disconnect the negative battery cables;

2. Start by removing the switches- the switch electrical plug and the high-pressure switch; 

3. Install the new switch and reinstall the electrical connector switch you removed in step two and reconnect the negative battery cable; and

4. Test the AC.

Take a look at some of our related articles below.

(1) liquid to boil –
(2) warm water –

Video Reference

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.