Converted to 134a - Question on Pressures and Troubleshooting

[DMan]

Hello,

I converted my R12 to 134a a while back and I have some questions. FYI, when I did the replacement, I changed the expansion valve, the drier, lubricant. I can't recall if I flushed the system..but I did use my vacuum pump to evacuate. Here we go:

Q1. I performed an archive search and someone there mentioned I should be shooting for 200psi on the high side with 134a. Is that still valid? Whats the corresponding low side pressure?

Q2. I added about 2.5 cans of 134a to the A/C system when I recharged it the other day. When I started, high side pressure was about 20 psi..when I was done High side pressure was about 95-100psi. The system was blowing *cool* air but I wouldn't say *COLD*. Sorry for the temperature descriptors - I didn't have my Fluke temp gauge handy. Anyway, do I have room to add more refrigerant? Should pressure be my guide?

Q3. If I keep adding and my pressure doesn't go up, I guess I should be looking for a leak. Is it possible the original compressor is 'weak', or is that not a normal failure mode?

Q4. Last q - which way do I hold the stinkin can when I recharge? Right side up or upside down? I've seen directions for both ways..does it matter?

Thanks in advance,

Denis Kefallinos

 

[digorok]

Leak check???

Q1. I performed an archive search and someone there mentioned I should be shooting for 200psi on the high side with 134a. Is that still valid? Whats the corresponding low side pressure?

A) 200 should be good, maybe higher, depends on outside temp. What is the low side reading???? Shoot for a low reading of 25 to 30 at 1500rpm.

Q2. I added about 2.5 cans of 134a to the A/C system when I recharged it the other day. When I started, high side pressure was about 20 psi..when I was done High side pressure was about 95-100psi. The system was blowing *cool* air but I wouldn't say *COLD*. Sorry for the temperature descriptors - I didn't have my Fluke temp gauge handy. Anyway, do I have room to add more refrigerant? Should pressure be my guide?

A) If it was 20 on the high side the system was empty. Did the gas leak out??? If so repair the leak. Did you add oil??? What is the low side reading???? I try to charge by low side pressure. Seems to work better. You need to have a fan blowing through the grill to keep the high side down. You can even mist some water on the condensor.

Q3. If I keep adding and my pressure doesn't go up, I guess I should be looking for a leak. Is it possible the original compressor is 'weak', or is that not a normal failure mode?

A) If the pressure won't go up, the compressor could be bad. Don't forget to put a fan in front of the grill. Need the low side reading.

Q4. Last q - which way do I hold the stinkin can when I recharge? Right side up or upside down? I've seen directions for both ways..does it matter?

A) You can charge liquid (up side down) to the accumelator, but not all at once. You'll need to watch the low side gauge to be sure the pressure stays below 60.

 

[DMan]

Great Answers Digorok! Thanks!