Will an A/C compressor engage is there no refrigerant (pressure) in the system?

Hendog · Hendog's Garage

I have not used my A/C since I bought the car over 14 years ago. It was converted to R134 by the PO. That being said it was barely discernible whether it was actually "working" when I brought it home. I don't care much for A/C and so I simply removed the compressor belt.

Now I'm curious to get it going again. I have no idea if there is ANY refrigerant in the system. I was told an A/C compressor clutch would not engage if there was no pressure in the system. I installed the compressor belt and only momentarily turned on the A/C to see if the compressor clutch would engage; and so it did! The clutch engaged. I only let it run for 1-2 seconds to see if it would engage. I don't want to run the compressor and damage it if there is no refrigerant or not enough. So, does this mean my A/C system is pressurized?

Thank you,

spuggy · 06-25-2018, 08:27 PM

Well, different car/system - but when I bought my 944, the A/C clutch would engage if the button was pressed, but it didn't go cold.

After a few years, I figured it'd be useful for getting fog off the windshield or a hot day, so got it checked out; apparently all the refrigerant was gone, like the PO had said. Had the system pressure checked and re-filled - all fine.

Rawknees'Turbo · 06-25-2018, 08:38 PM

If no previous owner added a high/low pressure switch to your 911, then the compressor clutch will engage if the system is completely discharged or even if it is full of goat pizz (aka - no pressure switch installed by the factory - who knows why as they were widely in use when your 911 was made).

T77911S · 06-26-2018, 02:50 AM

no it does not mean it is pressurized.

you need to put gauges on it to check.

Pazuzu · 06-26-2018, 08:01 AM

I would not try to run a system that has sat for 14 years. It's full of humidity, the oil that was leftover has turned to goo, there is probably rust inside the system...basically, it'll be a mess.

That system will require complete dismantling and examination of each part.

T77911S · 06-26-2018, 10:49 AM

I could only imagine how long my 86 comp did not run. just got it going 2 weeks ago.

it should not have humidity in there unless it was opened. then I would just drain the oil and replace.

Hendog · Hendog's Garage

Quote:

Originally Posted by T77911S

I could only imagine how long my 86 comp did not run. just got it going 2 weeks ago.

it should not have humidity in there unless it was opened. then I would just drain the oil and replace.

Any idea how long yours didn’t run? (Ballpark?)
Ya, I don’t think the sky is falling, but I may consider rebuilding the Denso compressor just to freshen up the seals and such. Then I have one hose I will want to replace because it has chafed against the engine lid hinge.

wayne robson · wayne robson's Garage

I have PM you, this may help.