View Single Post
JFairman JFairman is offline
Registered User
Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Originally Posted by gsxrken View Post
With my manifold setup, I can use the vacuum pump to draw down all of the lines right up to the quick connectors and to the 30lb bottle of r134. This may not be possible with the various manifold setups and their configurations, but take a look at yours and see if it's possible.

On edit- Jeff I see you're in NNJ- you're welcome to borrow my rig. I'm in 10598
I have Mastercool USA made manifold gauges. I can draw a vacuum throughout the entire thing and all 3 hoses but you never get 100% of the air out.. it's impossible while you're on earth.

By purging all the lines and the brass manifold everything is screwed into you have them 100% filled with AC refrigerant and nothing else. This way nothing is going into the AC system other than refrigerant and refrigerant oil if you're adding any oil.

When I do an AC charge I do a 3 hour evacuation with a high quality Robinaire two stage vacuum pump. It's amazing the electric motor on it even says made in USA!

Then I let it sit overnight with the gauges and hoses still attached. Then check it next day and if it's still holding a vacuum I run the vacuum pump another 3 hours. Probably more than needed but there is over 40 feet of AC hose in a 911 and the receiver drier, front condenser, and evaporator with expansion valve are around 20 feet of hose away from the compressor so it can take a while for all the moisture to boil out of those places and make it's way to the shrader valve on the compressor while nothing is moving through the hoses.

After getting it all charged as good as you can you can still improve how cold the AC vent temps gets by "sweeping" the system. Do that after it's fully charged and has run a little by slowly loosening a hose fitting from the front condensor and let the refrigerant leak out.
Let it out slowly so you don't blow much oil out with it. Then tighten the fitting when regrigerant almost stops coming out. By doing this any moisture that was still in the system mixed in with the refrigerant got blown out with the refrigerant while it was leaking out and pressure was equalizing.

Then evacuate it again as said before and charge it again. Doing this might make vent temps a little colder if there were any remnants of air and moisture still in the system.
Good luck with it.
Old 07-22-2017, 10:44 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)