Drop in PSI when "revving" the engine?

Hello DAVID VITTITOW,

Unfortunately, the can hooked to the low side is not an accurate way to measure system pressure or to refill an Automotive A/C system.

You need either a machine or a set of gauges and a tank of refrigerant. Unfortunately, the refill cans you buy are a gimmick and that's all.

The reason for this is the refrigerant and oil need to be added at a very specific amount or it will damage the system.

Now there could be something going on like a clog possibly but without the proper tool to measure it we don't even know if any of the readings are correct, especially because we can only measure one side.

These are sealed systems and refrigerant should not be leaking from them unless a component is faulty.

Can you tell me what symptoms you were having that caused you to refill or top off the system? You stated it wasn't working well, could you elaborate for me?

Thank you,
Brendon

Hello DAVID VITTITOW,

You are very welcome. I am here to help.

Pressure will drop on the low side as RPM increases and high side will go up in pressure. It also depends on the ambient temperature.

If pressure is too low the system's low pressure switch will turn the compressor off.

In Georgia especially if he is in traffic, the A/C won't work as well because there isn't air moving over the heat exchanger/condenser. The cooling fans should help but they can only do so much.

If it gets better driving down the road as opposed to sitting in gear in traffic then this is normal to an extent.

If it is too much of a temperature difference, then getting an A/C machine on it and having it checked and refilled might be a good first step. They will pull a vacuum on it for about 20 minutes and see if there are any leaks.

You can also get a gauge set and check the pressures yourself. I will add an image of them for you.

I am also adding a temperature chart for you. These ranges are approximate values. Keep in mind if you do use gauges to check it, some refrigerant will be lost.

Personally, I would run it for a while and have him keep an eye on it and see if it gets worse.

A good accurate way to measure the temp coming from the vents is with a food thermometer or something similar. He could use this to keep an eye on the temperature. They have ones that clip onto the vent as well.

Hope this helps.

Thank you,
Brendon