95 C4 Y-body corvette
Thread Starter
Staging Lane
Joined: Oct 2020
Posts: 86
Likes: 7
From: St. Louis MO
95 C4 Y-body corvette So I just picked up some manifold gauges to recharge the a/c system in my girls c4. Does anyone have the pressure readings as described in the FSM for the vette? Is it the same as a z28? If so I have the FSM for a 95 z. Thanks
This will be my first time recharging a system correctly(low and high side gauges). All the past times was with that "dummy gauge" that comes with the kit. Any insight on the procedure would also be helpful.
This will be my first time recharging a system correctly(low and high side gauges). All the past times was with that "dummy gauge" that comes with the kit. Any insight on the procedure would also be helpful.
This entire procedure is out there for study. If it’s your first time, write down all the steps precisely so you don’t forget anything as you go. Even do a run-through to get familiar with everything to avoid any missteps. The 3 biggest things I’d mention are:
1) You’ll need a vacuum pump to draw it down to as close to absolute vacuum it’ll go. And then hold it there for a couple of hours at least. Techs that worked for me at a Honda shop 15-16 years ago would always leave them overnight for bulletproof assurance the system was leak free.
2) when adding refrigerant, to prevent introducing air into the system you’ll need to purge the refrigerant line briefly to push out the air that’s in the hose when you connect the refrigerant can. Then open it at the manifold and let the system draw in the refrigerant.
3) amount and type of oil and refrigerant weight are critical.
1) You’ll need a vacuum pump to draw it down to as close to absolute vacuum it’ll go. And then hold it there for a couple of hours at least. Techs that worked for me at a Honda shop 15-16 years ago would always leave them overnight for bulletproof assurance the system was leak free.
2) when adding refrigerant, to prevent introducing air into the system you’ll need to purge the refrigerant line briefly to push out the air that’s in the hose when you connect the refrigerant can. Then open it at the manifold and let the system draw in the refrigerant.
3) amount and type of oil and refrigerant weight are critical.
It usually goes by weight, which is 2lbs of R134A on the C4. The gauges will fluctuate depending on ambient air temp, but I like to see 35-40PSI on the low side, and 210-250PSI on the high side.
Thread Starter
Staging Lane
Joined: Oct 2020
Posts: 86
Likes: 7
From: St. Louis MO
Thanks for the input. I've watched a bunch of youtube videos trying to get myself familiar with this process. I've read that the low side will hoover around freezing in relation to psi, and the high side is 2- 2.5x the outside air temperature. I've also read to introduce the refrigerant thru the low side and keep the high side closed on the manifold? I'm assuming that if there is some static pressure in the line then the system is still sealed and doesn't require a vacuum?
I'll check static pressure and go from there I suppose. I'd assume everything to be in working order. It's a 95 with a little under 12k miles. Thanks again
I'll check static pressure and go from there I suppose. I'd assume everything to be in working order. It's a 95 with a little under 12k miles. Thanks again
Yes, always add refrigerant on the ‘low’ side. More accurate descriptions are ‘suction’ and ‘discharge’ side. The problem with working on a system previously filled with refrigerant and oil is if there’s any refrigerant left in the system,
you can’t weigh it. Usually the assumption is there is none which may be inaccurate and result in an overfill. Oil can leak out too. All
depends on where your leak is. It’s likely a system this old will develop additional leaks at o-rings once refilled. Not trying to discourage you, but the DIY at home scenario is best with a completely dry system with a new drier/desiccant where you know what you’re adding in refrigerant and oil is an accurate amount of both. Equipment for evacuating all the old oil and any refrigerant that may remain is usually beyond the budget of most of us DIY guys. To minimize the cost at a shop for a simple evac/charge, we can go through the system, replace o-rings, schrader valve cores, orifice tube, etc and leak test with a vacuum pump. A shop will evacuate the system, pulling out the old oil and verify your home repair is leak free, and then charge the system with an accurate measure of oil and refrigerant.
you can’t weigh it. Usually the assumption is there is none which may be inaccurate and result in an overfill. Oil can leak out too. All
depends on where your leak is. It’s likely a system this old will develop additional leaks at o-rings once refilled. Not trying to discourage you, but the DIY at home scenario is best with a completely dry system with a new drier/desiccant where you know what you’re adding in refrigerant and oil is an accurate amount of both. Equipment for evacuating all the old oil and any refrigerant that may remain is usually beyond the budget of most of us DIY guys. To minimize the cost at a shop for a simple evac/charge, we can go through the system, replace o-rings, schrader valve cores, orifice tube, etc and leak test with a vacuum pump. A shop will evacuate the system, pulling out the old oil and verify your home repair is leak free, and then charge the system with an accurate measure of oil and refrigerant.
Thread Starter
Staging Lane
Joined: Oct 2020
Posts: 86
Likes: 7
From: St. Louis MO
I saw a video by scanner danner on youtube. He charges the system with nitrogen and checks for any leaks with soapy water. It's suppose to rain heavily all weekend here so I doubt I'll get to check the system out. I plan on running static pressure first and go from there. If anything, I'll get the system evacuated and start fresh with a vacuum. Thanks again for the correct terminology and ball park pressures. Appreciate it
