Automotive Air Conditioning Information Forum

Hi All,

My question is regarding constantly running ac compressors. My mechanic is coming to install a new AC compressor and told me that he will add oil (110cc PAG) and I would be ok to drive to the local garage to get the system refilled with refrigerant. Everything I have read says not to run the compressor and to bypass it with a shorter belt, as driving a few km to get it regassed may damage the compressor.

I would appreciate some input form the knowledge on this forum as I have zero experience of AC systems.

Would I be ok adding R123 from a re gas kit to get the car to have it properly vacuum emptied and regassed ?????

TIA !

Easy options:
1. Turn OFF the HVAC button before starting the engine.

2. Unplug the harness to the compressor

3. Remove the fuse for the compressor

It's OK to just let the compressor's pulley freewheel. If somehow your pulley is locked up to the compressor drive plate, you'd have to remove the belt if it has a separate belt. Do not add refrigerant for this issue.

If you mean "constantly ruining AC compressors", likely you have schmutz in the system from a previously malfunctioning compressor.

Cusser wrote: Fri Apr 03, 2026 6:08 am Easy options:
1. Turn OFF the HVAC button before starting the engine.

2. Unplug the harness to the compressor

3. Remove the fuse for the compressor

It's OK to just let the compressor's pulley freewheel. If somehow your pulley is locked up to the compressor drive plate, you'd have to remove the belt if it has a separate belt. Do not add refrigerant for this issue.

If you mean "constantly ruining AC compressors", likely you have schmutz in the system from a previously malfunctioning compressor.

Yep, just don't run the a/c w/o refrigerant. The belt riding on the pulley is normal operation w/o turning the a/c on, no harm.

Kindly post the year, make, model, engine size, and mileage for your vehicle. Is this a US-spec or non-US-spec vehicle?

Sorcerer33 wrote: Fri Apr 03, 2026 3:02 am My question is regarding constantly running ac compressors.

Your topic says, in part: "...re constantly running ac compressors." And your post above states essentially the same thing. Do I understand correctly that this is a direct-drive compressor—that is, the compressor runs whenever the engine runs, and that the compressor does not have a magnetic clutch?

Sorcerer33 wrote: Fri Apr 03, 2026 3:02 am My mechanic is coming to install a new AC compressor and told me that he will add oil (110cc PAG)... .

Why are you having the compressor replaced?

That amount of PAG oil, 110 cc, equals 3.7 fluid ounces for those of us in the USA. That might or might not be sufficient depending on how much the mechanic drains out of the old compressor and/or the manufacturer's specification for oil (the under-hood decal, if present, takes precedence).

Sorcerer33 wrote: Fri Apr 03, 2026 3:02 am Everything I have read says not to run the compressor and to bypass it with a shorter belt, as driving a few km to get it regassed may damage the compressor.

For a direct-drive compressor, your statement is correct.

For a compressor having a magnetic clutch, the clutch shouldn't energize to drive the compressor *anyway* if an otherwise correctly operating system is low on refrigerant or is completely empty. It couldn't hurt to take the precautions previously mentioned, though.

Sorcerer33 wrote: Fri Apr 03, 2026 3:02 am Would I be ok adding R123 from a re gas kit to get the car to have it properly vacuum emptied and regassed ?????

Do you mean R-134a or the newer R-1234yf refrigerant? In any case, I never recommend that vehicle owners use one of those "kits" to recharge a system, regardless of the refrigerant. The only proper way to charge or recharge a system is to *precisely* weigh-in pure refrigerant in the exact amount, or have it done at a professional shop that has a machine to complete the process.

To do it yourself, you would need some basic professional tools: a Manifold Gauge Set, a vacuum pump capable of drawing the system down to 29.9 InHg (Inches of Mercury) at sea level, a precise refrigerant scale, a source of pure refrigerant (no additives), and the knowledge to complete the job.