HELP - Need to rent a decent A/C vacuum pump

[rapaint66]

So I've replaced most of my A/C components and was able to pull 26" of vacuum and hold it overnight. Running high head pressure after charging with freon. Everything I read indicates this is due to non-condensibles in the system and that 30+" is required to boil out the moisture. The pump I have been renting from AAA is only capable of 28". Where can I find/rent a decent vacuum pump in BR? I'd hate to spend $200.00 on something I will only use once.

 

[LS1RX7]

An evac and recharge would prob be less than $100 at most shops. They could recover the freon in the system and re-use it and not charge extra for freon, oil, etc. Too much oil could cause same issue though. Also did you flush the condenser and is the fan working well?

 

[Charles1959]

View attachment 29119

According to this chart, if you pull 28 inches of vacuum on a day like today (mid 90's temp) you will boil the water out of your system. I used to sell Robinaire A/C equip and their vacuum pumps only guaranteed 28 inches of vacuum. Keep in mind that the longer you keep the system in vacuum the more complete the evacuation will be.
The difference in moisture content in your a/c system when pulled to 28 inches vs 30 inches is negligent. I believe that you might be talking one or one and a half degrees cooler at 30 inches...if that much. I'd pull it to 28 and let it run for an hour then shut it down and check for leaks.
If you are having non-cooling issues, the extra 2 inches of vacuum ain't your problem. You've probably got another type restriction somewhere.
Good Luck
Charlie

 

[rapaint66]

View attachment 29119

According to this chart, if you pull 28 inches of vacuum on a day like today (mid 90's temp) you will boil the water out of your system. I used to sell Robinaire A/C equip and their vacuum pumps only guaranteed 28 inches of vacuum. Keep in mind that the longer you keep the system in vacuum the more complete the evacuation will be.
The difference in moisture content in your a/c system when pulled to 28 inches vs 30 inches is negligent. I believe that you might be talking one or one and a half degrees cooler at 30 inches...if that much. I'd pull it to 28 and let it run for an hour then shut it down and check for leaks.
If you are having non-cooling issues, the extra 2 inches of vacuum ain't your problem. You've probably got another type restriction somewhere.
Good Luck
Charlie

Thanks for the chart info and advice. I really appreciate it! I can not imagine where else there might be a restriction. I have blown 134a solvent and 100 psi air through the entire system for hours on Sunday. Unless the compressor itself can be restricted?? I think I'm going to rent the AAA pump again and crank my engine up. That should get the ambient temperature up in the compartment high enough to allow 28" to work for certain. Also not opposed to dropping $100 to get someone to do this for me as LS1RX suggested. Thanks again!

 

[97z71stepside]

I'll rent you mine. It's a 6 cfm pump and will pull 30 inches of vacuum.

 

[Gus McCrae]

An evac and recharge would prob be less than $100 at most shops. They could recover the freon in the system and re-use it and not charge extra for freon, oil, etc. Too much oil could cause same issue though. Also did you flush the condenser and is the fan working well?

$200, I just replaced the compressor, orifice tube and accumulator on an S10. They recovered and recharged the system.... oh, they replaced one of the Schrader valves. Many shops didn't want to bother since I wasn't giving them $900 to do everything for me.

I was out of pocket about $500 when I got done.

 

[stag0608]

You need a micron gauge to see if you pull a good vacum. You need to pull down to 500 microns. Also should not reuse the same freon it is contaminated already. You should also never use air to blow out a system! If you had the dryer on when you did that you plugged it up. Next time you need to use dry nitrogen.Also no vacum pump can pull down to 30inhg absolute 0 is 29.9. You need micron gauge.

 

[robinfly]

without a good air flow thru your condenser the high side pressure will be excessive, so make sure your fan is working properly and the radiator and condenser is clean. Can also be a bad compressor.

 

[stag0608]

It's not the compressor, but yes make sure your condenser is clean and your getting air through it.

 

[robinfly]

It's not the compressor, but yes make sure your condenser is clean and your getting air through it.

True, brain fart. thanks for the correction

 

[sparky_benton]

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