A/C Evacuation

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Jul 24, 2005 | 09:04 PM

drswitala

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From: Brownstown MI.

A/C Evacuation

How do you evacuate the A/C system prior to recharging with R134 on a 1980?

Jul 24, 2005 | 09:24 PM

big_G

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From: Austin Texas

You need a vacuum pump that can pull down a 30 in. vacuum, these are used by a/c shops...professional equipment.

Jul 25, 2005 | 08:49 AM

PortDawg

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From: Gloucester Va

St. Jude Donor '05

It's pretty important to do this right, otherwise you'll have moisture in the system and your AC won't work right. The vacuum does a couple things: it makes sure you have a seal and it sucks all the excess moisture from the system. Oh and if you're replacing the compressor, spend the money on a new one...the rebuilds aren't worth the money....

BTW, I just did mine and now I've got nice cool air.....

Good Luck !

Last edited by PortDawg; Jul 25, 2005 at 12:34 PM.

Jul 25, 2005 | 09:32 AM

zwede

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From: Plano TX

Years ago I got a little robinair AC pump off ebay for $160. That thing has paid for itself so many times.

Before I got the robinair I rented a pump. I think I paid $15/day.

Jul 26, 2005 | 08:55 PM

drswitala

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From: Brownstown MI.

YAHOO! Shes blowin cold! The solution was 4oz of oil which I introduced to the system after totally discharing it. Followed up with 2 cans of R134a. It appears that the R134a supplied with the retro kit I used did not have a sufficiant amout of oil pre added to the coolant as it claimed. Also put a manual shut off valve to the heater core which helps keep floor cooler.

Jul 26, 2005 | 10:56 PM

zwede

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From: Plano TX

Unless you pulled 30" of vacuum on it before charging it's not going to work right. There's moisture in the system which corrodes the compressor and plugs stuff up when it freezes.

2 cans of r134a sounds like it's not enough. My 71 needed 3.

Jul 27, 2005 | 04:49 PM

Rockn-Roll

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From: Carmichael CA

Have a shop do it. Not only do you need to get some vacuum going to get out all the gases. But, you need to flush the system including the condensor to get out all the old oil. I think I paid my shop $150 for the entire flush and evacuation. They mechanic spent several hours flushing the system which entailed pouring A/C flush into the system and sucking it out along with the oil that it collects using an A/C service machine.

I actually tried using just a house hold vacuum cleaner which I ran for several hours and it worked OK...got most of the air out and the air temp out of the vent was in the mid 50ºs F. But, after a flush and evacuation the temp dropped to the low 40ºs...a big difference between cool air in the mid 50s and cold air in the 40s.

I try to do everything myself...so that it gets done right mostly. But, in the case of the A/C flush & evac I recommed taking it to a shop...the A/C system is an old system, but a typical GM system which was used in all their vehicles for a decade or two. Some shops actually may not have the fittings for the OEM nipples.

Jul 27, 2005 | 05:43 PM

zwede

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From: Plano TX

I flushed mine myself using this flush gun:

You fill it 1/3 with AC flush and charge it up with compressed air to 110 PSI. Worked real well. Got lots of gunk out.

Edit: Got it at NAPA a few years ago for $80.