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question about pulling a vacuum

drptop70ss on Mon April 27, 2009 9:29 PM User is offline

Year: 1995
Make: chevy
Model: caprice
Engine Size: 350
Refrigerant Type: r134
Country of Origin: United States

Getting closer to finishing up my retrofit of a 70 chevelle with 1995 caprice A/C components, quick question on pulling a vacuum since I just ordered a vacuum pump.
I have worked with vacuum, large vacuum pumps that will boil out any oil or moisture in a system until the system is dry. I understand I have to add the 8oz of pag150 oil into the suction side of the compressor before buttoning up the system, but how do you know when you have reached "base pressure" with the vacuum pump since there will be oil in the system? Since the pump will not be strong enough to boil out the oil, but hopefully strong enough to remove moisture, what is the general accepted base pressure when pulling a vacuum? If there is a leak I obviously wont get the system down as low as it should go but I would like to know right away if things look tight or not. Thanks!

Chick on Mon April 27, 2009 10:02 PM User is offlineView users profile

Pull your vacuum down, 29.9 at sea level, (you lose about 1hg for every 1,000 above sea level) and run it about a half hour, shut it off and see if it holds, might take a couple pulls until it holds steady, then charge the system up, it won't pull the oil out and you'll be fine..hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

drptop70ss on Mon April 27, 2009 10:54 PM User is offline

thanks, I will have to see what type of gauge comes on the pump, I am used to working with mTorr readings, but if it is in Hg that will be fine..should know in a couple days when the pump gets here.

One other question, regarding the accumulator, what is inside of it? Mine is clean, any reason I cant reuse it? Is there a decissant in it or is it just a can since it is not a dryer? Or is it? Still learning about the guts of the system.

Chick on Tue April 28, 2009 6:22 AM User is offlineView users profile

A new Accumulator is just about $19.00 and is the best insurance you can buy for your system, don't use the old one. The desiccant is in it and is sure to be water logged by now. Just my opinion. Also, you pull your vacuum thru your gauge set, and the low side will read vacuum when you pull down..Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

drptop70ss on Tue April 28, 2009 5:18 PM User is offline

thanks, your help is always appreciated..I will use the original accumulator for mock up and order a new one for the final install. The fuel injection conversion will take less time than I am spending on this A/C build

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