Question about A/C

First if you don't know what you are doing be careful or leave it to a professional. That being said, I'll offer some thoughts.

Usually the low-pressure lines are larger and the high-pressure lines are smaller. This is because the same amount of refrigerant moves through both but at higher pressure it needs less space.

The line that leaves the compressor and goes to the condenser is a high-pressure line (it carries superheated liquid) and so is the line that leaves the condenser going to the evaporator (it carries liquid). The line that leaves the evaporator going to the compressor is a low-pressure line (it carries gas).

On a home air conditioner the large line is the low side. On an auto or truck air conditioner the line that leaves the compressor (it has the belt driving it) going to the inside of the vehicle is the low side.

Now if you don't have gauges and understand charging methods it is just as easy to over-charge, as it is to have a low charge. The A/C won't work right either way. I have worked HVAC for years. In most cases the problem is not a charge problem or just a charge problem.

If the unit is out of refrigerant you have other problems too. There is the leak. If it has been run empty it needs to be evacuated to remove moisture. If it is an auto/truck unit without refrigerant it will never work unless the receiver/dryer is replaced.

And then there are the different refrigerant types and the certifications needed to even purchase them. Believe me repair may be expensive but it's not because anyone is making a killing. Last time I bought R-22 it was $362.00 for 30 # and that was a few years ago. That is what you need for an older house A/C. I think many/most vehicles are R-134a now. Whatever you are looking at should have placards with the refrigerant type.

Overcharging can damage compressors. Mixing refrigerant can be costly too. Charging a vehicle A/C that has lost all its oil will lead to a damaged compressor. If you are charging a vehicle, with little or no refrigerant, you will have to find the low-pressure switch and jump it to get the compressor to run and take the refrigerant.

Good luck.

 

Good one. That is priceless.

 

If it works the low side(suction) will be cold, the high side will be hot.