Auto AC leak question
 

A seal on my receiver/dryer doesn't hold vacuum - I replaced the seal and added an o-ring and can get it to hold vacuum but I want to be able to test the system with around 50psi of air before I take it to the shop that will charge it up. My question is: how do I get air or some other non-refridgerant gas in through the manifold to test the system?

You may have to buy a hose with a fitting and then take it to a shop that will crimp an air hose fitting on it or one you can adapt it to.

What you need to get to is a 1/4" male flare. That will connect to the hoses on your gauge. A good hardware store will have the male flare to pipe thread fittings. Then, use other fittings to adapt to your supply hose (barb, couplings, etc).
Jurgen

I take the charge hose off and inject straight into the manifold with a rubber tipped nozzle on my air gun. You may have to remove a schrader valve on the manifold. Press the rubber tip on the manifold, open a valve, inject, close valve.

Charging with air will put a lot of moisture in there. Dry nitrogen is a better choice. If you use air pull a LONG vacuum, at least overnight. Receivers are the one part of a AC system pretty much designed to be replaced ever time the system is open to the atmosphere.

Ditto

Nitrogen is better, but I wouldn't say compressed air puts a lot of moisture in the system. It mainly depends on the condition of your air tank. I drain mine. Sure, some gets in there, but it also gets boiled off when under vacuum. Overnight is pretty liberal, but it's all dependent on the ambient temp and how well your vacuum pump works. Mine works pretty well, it's 100 degrees here and 20 minutes is more than enough.

My vacuum pump came out of a Robinaire machine, vintage '07. One fitting and wire it up!