Automotive Air Conditioning Information Forum (Archives)

79vetter on Mon July 18, 2011 7:54 PM

Year: 1979
Make: Chevy
Model: Corvette
Engine Size: 350
Refrigerant Type: R12

I have spent a lot of time and money getting to this point.
In summary, I installed a New R4 Compressor, New Evaporator, New Main Hose, New Orifice, New O- Rings, New Accumulator. I flushed the old Condenser using advice here and flushed the remaining lines. I have installed 4oz. of mineral oil in the compressor and 2 oz, in the Evaporator. I've got .25 oz. of dye in the Evaporator as well. I put a socket on the compressor and rotated it several times.
I rented a 1.5 CFM Vacuum Pump and Gauges and I evacuated for about 3 hours. It seems be holding vacuum just fine (overnight) according to the gauges.

All that's left : Install the the R12.

Here's my problem. My GM Service Manual has specific instructions on how to charge the system.
Places like this forum give instructions that differ from my manual. For example:

Gm Manual:
1) Start Car
2) Invert Can and install 1 pound
3) Turn A/C on to Norm - Blower to Hi (this will suck in the remainder of R12)
4) Use fan on Condenser

AC Forum:
1) install R12 with car off (1 person said install on the high side with the car off)
2) install as a Gas
3) bypass cut-off switch
4) bring idle up (1500 rpm)
5) heat can of freon

Doors /Windows Open or Closed
Not sure how to use the gauges as well.
I'm worried that I get in the middle of this and then run into problems.



Edited: Mon July 18, 2011 at 8:12 PM by 79vetter

JJM on Mon July 18, 2011 9:26 PM

Procedures aren't too much different, since the GM procedure you cited does say to get 1 pound in first, then turn the A/C on... so both procedures have the A/C off during the initial charge.

Bottom line is want to get in as much refrigerant as possible with the engine off, gas (tank upright) or liquid (tank upside down). Doesn't make a difference if it's through either the low side, high side or both. Once you've gotten as much in as the system will take with the engine off, close the high side valve, turn on the A/C, and charge as a gas (tank upright).

You already did all the hard stuff, charging is the easiest part.

Even though the system is still under vacuum and holding, you should still hit it with the vacuum pump for another 15-30 minutes before charging. Micron readings do rise over time.

Also, before charging, with both wheels closed, and the refrigerant tank connected, be sure to crack open the yellow hose (carefully) the gauge to expel any air that might be in the line, then proceed to charge.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com

79vetter on Mon July 18, 2011 9:29 PM

thanks for the reply....wth regards to cracking the yellow hose to purge air, can I just press the schrader valve (on the yellow hose at the manifold) until refridgerant comes out?

Also, I wonder what the difference is with starting the car vs. not starting the car? Since the A/C is turned off anyway?

Edited: Mon July 18, 2011 at 9:41 PM by 79vetter

TRB on Mon July 18, 2011 9:36 PM

Quote
Originally posted by: JJM
Even though the system is still under vacuum and holding, you should still hit it with the vacuum pump for another 15-30 minutes before charging. Micron readings do rise over time.



Also, before charging, with both wheels closed, and the refrigerant tank connected and open supply refrigerant, be sure to crack open the yellow hose (carefully) the gauge to expel any air that might be in the line, then proceed to charge.



Joe



When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com

Made a small edit to what Joe suggested. Just want you to understand the you want to bleed a small amount of refrigerant through the yellow hose at the base of the guages.



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

70monte on Tue July 19, 2011 11:24 PM

You can press the schrader valve on the yellow hose to vent any air in the system. That is what I do.

This is how I do my charging. After pulling a vaccum, I close both valves on the gauge set and disconnect the yellow hose from the vacuum pump. I then attach it to my can tap, purge the air from the yellow hose and then open the low side valve on my gauge set and let the vacuum in the system suck in as much of the refrigerant as it can. I usually have a bowl of hot water to put the can in to help the process along.

I then start the vehicle up and continue to charge until I'm positive the can is empty. I actually weigh each can with the can tap attached before and after to get an idea of how much refrigerant I put in the system.

I then repeat with each additional can.

I also have AC on Max with highest blower speed and windows and doors open. It's really a pretty simple procedure.

The biggest thing that I have to remember to do is purge the air from the yellow hose each time I change cans.

Good luck and let us know how it goes.

Wayne