AC pressure switch question

[bhw33191]

I think i need a new one. Can i replace this without losing my AC charge? Its just i don't know whats behind it and didnt know if there is a one way valve or not.

[Blt2Lst]

I am pretty sure you will have to discharge the system to replace the pressure switch since it does monitor system pressure directly.
Why do you think you need a new one?
Have you hooked up gauges to your system to see what is going on?
Inquiry minds want to know..

[bhw33191]

Originally Posted by Blt2Lst

I am pretty sure you will have to discharge the system to replace the pressure switch since it does monitor system pressure directly.
Why do you think you need a new one?
Have you hooked up gauges to your system to see what is going on?
Inquiry minds want to know..

For lack of better idea, i figured i needed a new one. At idle the compressor would stay on but when the RPMs are above about 1k it would cycle off and on every 5 seconds...which means it was a little annoying driving around with the AC on and it worries me about burning the clutch. I think its somewhat of a bigger problem than that though.

But please read on , I need someone elses opinion on what i should do. The low-down: Today the temp was around 95. Compressor acts the same as usual. Stays on during idle, blips on and off in above idle RPM. I just went out and turned the AC on, car was completely cooled off, felt the compressor and it feels excessively hot even though it was only on for about a minute. Maybe this is a lubrication problem, or maybe my belt is too tight? Don't know. I just realized the R134 i've been putting in this system says it contains the PAG lubricant you guys told me NOT to use...However, when i first filled the system about a year ago i DID put in a can of the right stuff "i think its Ester oil?". So maybe this lubricant mixing is causing the problem? Also, the compressor sounds a little noisy, almost like a crunching noise. Its not loud but its definitely there..who knows if its normal.

And one more Important thing to mention: Up until a year ago, my AC had not been working for at least 10 years. Found out there was a large crack in the aluminum condenser tube. When i fixed that, i never had the system cleaned or vacuumed "figured it wasn't a problem since the system had been dry". But that still doesn't rule out moisture/corrosion in the system. Anyway, it worked as soon as i filled it up. Maybe i need the system completely vacuumed and refilled strictly using that Ester oil?

[Blt2Lst]

Originally Posted by bhw33191

For lack of better idea, i figured i needed a new one. At idle the compressor would stay on but when the RPMs are above about 1k it would cycle off and on every 5 seconds...which means it was a little annoying driving around with the AC on and it worries me about burning the clutch. I think its somewhat of a bigger problem than that though.

But please read on , I need someone elses opinion on what i should do. The low-down: Today the temp was around 95. Compressor acts the same as usual. Stays on during idle, blips on and off in above idle RPM. I just went out and turned the AC on, car was completely cooled off, felt the compressor and it feels excessively hot even though it was only on for about a minute. Maybe this is a lubrication problem..and the compressor is failing because of it? I just realized the R134 i've been putting in this system says it contains the PAG lubricant you guys told me NOT to use...However, when i first filled the system about a year ago i DID put in a can of the right stuff "i think its Ester oil?". So maybe this lubricant mixing is causing the problem? Also, the compressor sounds a little noisy, almost like a crunching noise. Its not loud but its definitely there..who knows if its normal.

And one more Important thing to mention: Up until a year ago, my AC had not been working for at least 10 years. Found out there was a large crack in the aluminum condenser tube. When i fixed that, i never had the system cleaned or vacuumed "figured it wasn't a problem since the system had been dry". But that still doesn't rule out moisture/corrosion in the system. Anyway, it worked as soon as i filled it up. Maybe i need the system completely vacuumed and refilled strictly using that Ester oil?

You should still hook up some AC gauges to see what the pressures are in the system (this is AC diagnosis 101), A cycling compressor can mean the system is low on charge.
The crunching sound could be the clutch/pulley bearing starting to go or the compressor itself is about to go. If the system was not operating for 10 years and it was open to the environment all that time, your system most definately is contaminated.
Just changing the oil and refilling with r134 is not the correct way to do the conversion.
To get your system working properly, you will probably need to :
1. change the compressor
2. new receiver dryer and orifice tube, maybe hoses.
3. completely flush system of old oil and contaminents
4. evacuate and refill system

It won't be cheap to do but you will be cool afterwards

[bhw33191]

Thank you so much for the details. Might have my mechanic do the AC, or at least clean the system since i don't have a vacuum..but anything else i could definitely do myself. Oh and one more thing. Specifically, the PSI is at 35 at idle, which seems just about right. I think i definitely have a dirty AC system on my hands. But sheesh i'm still happy it sort of works considering the situation.

[j cAT]

Originally Posted by bhw33191

Thank you so much for the details. Might have my mechanic do the AC, or at least clean the system since i don't have a vacuum..but anything else i could definitely do myself. Oh and one more thing. Specifically, the PSI is at 35 at idle, which seems just about right. I think i definitely have a dirty AC system on my hands. But sheesh i'm still happy it sort of works considering the situation.

when converting this old R12 ac system you must use the conversion oil....PAG 150 is for R134 GM designed vehicles...since this was mixed , it would be best to have an ac tech clean out the total system . then replace the ac compressor and using the conversion oil..

they have the proper chemicals and equiptment to do this ..