1970s 1970 AC R12 how to charge?

[jmurrayent]

1970 Deville, just installed new AC compressor and drier, replaced all o-rings, flushed the system and held vacuum at -28psi overnight.  I understand the system takes 4lbs. of R12.  I had a partial 15 lb. cannister and a full 15 lb. cannister. I emptied the partial can and used very little out of the full can trying to achieve 30 psi (low side) and 175 psi on the high side.   How do I know when I have installed the right amount of freon?  I think I may have overcharged it.  I currently have 30psi on the low pressure side and 175psi on the high side at idle.  No bubbles in the sight glass on the guage.  Its blowing luke warm at the vents.  Can someone offer advice?  Thanks!

[Dave Shepherd]

Couple of basic things here, is the system in full a.c. mode, is the water control valve not allowing any hot water into the heater core, is the low side pipe cold to the touch? Of course the right way to charge system  is to use a charging station to control the 4lb charge requirement.

[jmurrayent]

Hi Dave, yes the cold side pipe is cold, not frosty cold, but pretty cold.  The dial is set at auto, but I"ve also tried it on full high.  Is there any way to charge the system using the pressure gauges and site glass or is 4 lb volume the only way? Thanks

[Dave Shepherd]

Now that is charged the system would have be evacuted with the proper equipment and recharged with the controlled amount of 4lbs. That just ensures the proper amount is in the system.

["Cadillac Kid" Greg Surfas 15364]

With the pressures you report (30/170) I would suggest that the refrigeration side of the system is functioning and not over charged. I would look elsewhere for the issue and your '70 I would suggest disconnecting (and plugging) the large vacuum line that goes to the programmer actuator, that is ocated at the firewall on the driver's side and has several small vacuum line connected to it. Just disconnect the large vacuum line. This should rive the system into full cooling.
You may also have an issue with the purge vent, but check one thing at a time. I would not do anything with the refrigeration system for now.
Greg Surfas

[jmurrayent]

Thanks Greg, I'll give that a try...

[jmurrayent]

Greg,

I took my first drive today with 70 degree outside temp here in Reno.  The AC worked but I can feel the temp fluctuating from super cold to luke warm.  The control is set in the auto mode with the temp dial at 65.  When I got home, I disconnected the large vacuum hose on the silver cannister on the firewall and the AC went full cold and full fan like it was turbocharged  .  Does this mean I have to look into the control unit at the firewall?  I think I'll order Cadillac Tim's AC manual, I have one for my '65 and it is excellent but I think the '70 is different......

[TJ Hopland]

Ya sounds like a control problem.  Tim's manuals are worth the money.  Much easier to understand and go through the troubleshooting than the factory manual.