Truck AC question

[bensonwe]

I have an ac question on my gmc sierra. I was wondering if a vac can be pulled on a charged system without loosing the refrigerant? I replaced a failed line and pulled a vacuum for and hour, charged it with dye and ran the ac for about 10 miles. No leaks. But i dont think the vac pull was enough. Now i want to pull another vac for longer issuring as much contaminants are removed as possible. Thanks for the input.

[Hossfly]

No you can’t pull a vacuum on a charged system. You pull a vacuum on a system after repairs are performed and leak tested. You wont be able to separate the refrigerant from the air that’s inside. You will loose all that you’ve put in. An hour is long enough to get all air out but not any physical water if any.

[Jniedbalski]

You also can’t pull a vacuum and then run the car ac. There is a low pressure cut off. It cycles when low and won’t turn the compressor on at all if to low. Pull the vacuum after repairs 1/2 hour is plenty. Check gauge for vacuum close valves turn off pump. Let set ten to 30 min check for leaks, low pressure gauge goes up. If not charge and run it

[Jniedbalski]

If you have the system apart for a long time Ten min or more I like to change out the desiccant on the low side also. It’s in the aluminum tank on Chevys and gmc’s

[Winger Ed.]

Put it on 'double secret probation', and keep driving.

It'll tell you if ya did a good repair.

[jim147]

You don't think you pulled enough vacuum?

By what? Are the needles bouncing? Going by your first post you don't have a vacuum gauge to see exactly what you pull so it's a close guess.

[.429&H110]

20 years in A/C, hockey rinks, and freezers ice cream machines freeze dryers etc. Vehicle A/C is very forgiving to work on (good thing too). The best way to ruin them is to overcharge them. True of any closed cycle or Ruger. Recover all the refrigerant. Repair it. Pressure test with dry nitrogen if you want to. Nitrogen will chase air and moisture out. Dump the nitrogen to zero, vac for about ten minutes. Now it will suck in a little oil. How to know how much oil to add? You don't. The oil is likely stuck in the accumulator compressor condenser. If you recovered vapor only, you didn't get much oil, 2 oz would be a lot. If you accidentally blew out the charge, you likely lost a lot of oil. I had a oil flushing gadget that would clean burnouts and all the oil. Carefully change to the "good" vacuum pump, the one with new oil, vac 'til the micron gage says go or you get tired. Weigh new refrigerant into the high side. Start it up, finish charging by weight slowly into the low side. Now you can find out what was really wrong in the first place. I love that part. Start over.

There are a lot of A/C videos on utube and some are quite entertaining.

On some systems I could lock the refrigerant in a condenser/receiver, recover the low side vapor. They don't let me design cars. Last outfit I worked for billed $2 a minute. People thought I was gouging with $12,000 worth of equipment and a one ton van. 20 pound can of r-22 was $400 15 years ago. I had lots and lots. 507 404 134 all ready to go. I don't work there anymore.

I have a 2001 Tacoma here in AZ and never have added gas, A/C works fine.
How did Toyota build a twenty year system?

[jim147]

I think it's because you have never added gas. I find a lot of leaking shrader valves after people have kept adding the "freeze on" without fixing the problem.

[Three44s]

I am a farmer and dirt is our biggest boogie man for keeping AC systems going.

What this has to do with vehicles is that depending on their operating environment, they may fall into the same trap where heat exchanging, either dumping heat outside the passenger compartment or absorbing heat inside it.

My Hay Windrower has been a real pill. There is a ton of glass and I would do well to add some window tinting to reduce solar heating and lighten the load on the system but in the meantime I cleaned the condenser and evaporator inside and out and changed all the hoses, the compressor, the receiver/dryer and the expansion valve.

I hold my vacuum for 24 hrs after flushing with appropriate cleaner and purging and pressure testing with nitrogen.

But I did more!

The air inlet for fresh air had a LOUSY filter system and I built a custom air filter and fan system to increase the pressurization inside the cab. I instructed my operator to DILIGENTLY clean the radiator and condenser RELIGIOUSLY and NEVER EVER run that machine with the door open.

The system has since run flawlessly for two seasons straight without any Freon added. The cab actually self cleans now. I wish the evaporator was in an easier place to service but it is where it is (in a terrible place to access).

My operator is now banned from adding refrigerant. He blew the old compressor up and he got to run that machine for two miserable summers without AC. He thought he was “smarter” than me but he listens now!

He also received the honor of accessing that nasty located evaporator and he keeps that door shut as a result.

I did not pay enough attention to what compressor was the best until it became too late to gather a bunch of them up though. I know now that the old Delco A6 would be my choice as their capacity is unparalleled. I had a guy feed me a line on how terrible they are to work on. I watched a detailed video from a popular repair shop and the biggest thing is to accumulate the proper specialized tools and book mark that video!

I checked with a wrecking yard and they did not have a single A6 in the yard. I am not sure the Chinese knock offs of that compressor are worth fooling with?

I installed a Sanden knockoff and I was really worried as it was running very hot for a while but things leveled off after a while.

Three44s