How to Add Refrigerant When the Compressor Isn’t Running

 Yes, you can add refrigerant when the compressor isn’t running running

Most DIY recharge kits tell you to add refrigerant when the compressor is running. But what if it isn’t? This article explains how to add refrigerant when the compressor isn’t running.

Read This Important Fact Before You Add Refrigerant

The AC refrigerant (Freon) carries oil throughout the system to lubricate the compressor. If your AC system is low on refrigerant, it’s because you have a leak. When refrigerant leaks out, so does the refrigerant oil. A large leak means you’ve lost a lot of oil. If you simply refill the system with refrigerant and then run it, the compressor will self-destruct due to lack of oil.

Ignore the advice to jumper across the low-pressure switch

This is really a simple concept: If you jumper across the low-pressure cut-off switch to run the compressor when it’s low on refrigerant, it will run with low or no oil, which will destroy the compressor.

Instead, follow these steps to add refrigerant when the compressor isn’t running

Your goal is to increase refrigerant pressure in the system to the point where the low-pressure cut-off switch allows the compressor to run. Try this procedure

1) With the engine running and AC turned to MAX, connect your DIY AC recharge kit to the low-side port.
2) Squeeze the trigger to add refrigerant to the system.
3) Keep adding refrigerant until it won’t take any more. If the compressor clutch doesn’t engage, go to step 4.
4) Close the valve to the refrigerant can.
5 Fill a bowl with warm water and submerge the refrigerant can into the warm water. That will heat up the refrigerant, raising its pressure.
6) Open the valve and add more refrigerant.
7) Repeat steps 4 through 6 until the compressor clutch engages.

At that point, you’ve forced in enough refrigerant to raise pressure past the low-pressure switch cut-off point.

If that doesn’t work, find out if the system is empty

All car AC systems have a low-pressure cut-off switch to prevent the compressor from running if the refrigerant charge is too low or if the system is completely empty. If the compressor doesn’t engage, you must make sure the system isn’t empty by checking system pressure when the AC system has been off for at least 1-hour.

Using your recharge kit gauge, check the system’s static pressure (How to read static pressure). If static pressure is at or near 0, your system is empty. That means you have a major leak, and there’s now air and moisture in the system, which is seriously low on oil. If you recharge an empty system, it’ll never work properly and can damage the compressor.

©, 2023 Rick Muscoplat