72and86

I'm slowing learning how to do this right by reading online.
Whatever was in there has leaked out. I did a vacuum test on the system. It was 31 last night, this morning its 28-29 ish.

2 questions: How do I determine where the leak is w/o taking the entire system part? (I bought a new receiver/dryer. I'll replace that with the new green o rings and see if that helps...)

And how do I know if the PO hadn't already converted to 134a? Theres no sticker on the compressor saying so... (see above pic, previous posts).

lvmyvt76

call them???????

slofut

When you change to 134a you change or put adapters on the service ports that are a different size than r12 ports. Your AC tech will notice this right off. This is done to avoid mixing refrigerants in the system and service equipment.

72and86

Ive never had a seller reply to a question after 24 hours of them taking the money for the car. And I don't have his contact info.

72and86

DIY owners can remove them to use on other cars, but yeah I know what you mean. It's doubtful it's been changed over... Probably hasn't worked in years.

bucharli

systems in the 80's are much different, I just through 134a in and they work fine, these early vettes are a very different system. I just replaced all the components in my 69 and built it for 134a. the oil is a factor. 2oz per component and its a synthetic oil. the r12 replacement gas is not the same as real r12 but it will be cheaper to use that and do minor repairs then to set this system up for 134a. or do a lot of component cleaning and get a pov calibrated for 134a

72and86

Well I was going to try to replace the receiver/dryer but when I started to turn the nut going into it, the tubing from the condenser (its the condenser, right?) started to bend and kink. Not good. Also the stock dryer had a site glass on it, the replacement didn't.

I also read a GM report saying the existing oil in the compressor from R12 was not harmful when converting to 134a. So I said screw it, lets just see if I can get some cold air outta this beast.

After running vacuum on it for an hour, it looked good. (System was already empty). I added a can of R134a, then a can of Stop Leak, with Dye and then another can of 13Oz. R134a.

Sticker says 3.2lbs on compressor of R12. My calculations of replacement should be 42 (apprx) oz of 134a.

After 2 cans the thermometer at the vent read 49 degrees. The car ran at idle for about an hour. I didn't ad the last can yet as I going to see if there's any leaks.

bucharli

play it by eye. ambient temp plays a big factor in system pressures. best time to do it is in the hot sun.

71 Green 454

Were you using gauges? If so, what were your low side/high side readings after adding the second can?

bucharli

this may help. and the 1st scale on the gauges is vacuum the 2nd scale is 134a

72and86

I THINK when I was adding the 2nd can with the AC on MAX setting in the car, the gauge was reading close to 190-195 on the low side. The high side was closed so I don't remember.
After the car was shut off the LS gauge read about 72 psi.
Outside temp was about 65F when I charged the system.

bucharli

that should be your high side/red guage reading while running. or you read it in kpa not lbs. and make sure your reading the correct scale on your guages, there are 4 different ones. ambient temp and the running numbers is your best guide. not amount installed!

lvmyvt76

you had 190-195 on th LOW side, better step back, she is going to blow!!!!!!!! (high side reading???) outside temperature was too low to get good readings, need to check in higher temps.