F-BOMB

When hooking up a vacuum to the air conditioning for evacuation, do you hook up the vacuum to the low pressure port or to the high pressure port. I bought a cheap venturi vacuum from Harbor Freight and do not know which to hook it to.

zap89

Dude you ever figure it out ? I have bought one too and posted a similar question but like you no one has an answer

black89ws6

You hook it to the middle port on a set of manifold gauges. You can't pull a proper vacuum without them.

Once it's hooked up and running, I usually pull the vacuum on both the hi and low sides. The system will pull down to deep vacuum faster.

If you guys are using the venturi vacuums that hook to an air compressor, I hope you have a ginormous air compressor. Those rigs take a lot of compressor volume to pull a good vac, and you really need to vac it for a half hour minimum.

zap89

I have a 6hp 33gal Craftsman air compressor only a few months old. What do you or the other board members use ? Do you do it on your own or just find it easier to take it to a shop and let them them do that part ?
In Texas, A/C shops charge a premium for all work so I try to do as much of it as I can myself.
And thanks for the answer...

black89ws6

that should be big enough.

I have a 5cfm robinair vac pump that I use. I don't have a big enough air compressor for the venturi type pump.

Vacuuming isn't really something you can have someone do for you. The schrader valves in the port connectors are designed to hold pressure. not vacuum. If you unhook from a system under vacuum, it will let air in. If you were to have it done, have it charged as well. That would keep the air out.

CaysE

A schrader valve has a spring that should keep the valve closed under vaccuum at atmospheric outside pressure. If you're getting air in the system when you remove the vaccuum pump, replace the schrader valve.

zap89

So you are saying I should be able to take it to a shop have them vacum it and then go home and charge it ?
Thanks to the both of you for all your help..

CaysE

I don't see any problem with it as long as you're sure there are no leaks and your schrader valves can hold the vaccuum. Personally, I would take apart the system to replace the o-rings and check the orifice tube before getting it charged.

zap89

My compressor froze up so it was replaced as was the dryer, orifice and orings. Now to vacum and charge..the "feels like" temp is like getting close to 100 so I am moving on this quick

zap89

Well guys thanks for all the help. It was a great leanring experience, I vacumed it and let it run for like 45 mins, checked for leaks, charged it and have 48 degrees coming out of my center vents ! ahhhhh now I can sit on these Houston freeways all day. I rented the vacum and gagues from Autozone (Put down deposit and then get it back) it worked like a champ

CaysE

A/C is the best invention ever! Good job.