A/C freshen up

[Michael Star]

My 70 GMC came with factory air (compressor needs to be replaced) but it worked before the compressor went out. What other things should be replaced along with the compressor?

[leddzepp]

The drier...possibly expansion valve. I know most parts houses will not warranty the compressor unless a new drier and expansion valve are used.

[mrein3]

For sure you want a new receiver dryer (P/N 33215 at Rockauto.com $10.20). You must replace this item every time you open the system up.
If you're worried about the expansion valve replace it (P/N 38652 at rockauto $17.30).

What I would do if I was you I'd adjust the POA to work with R134a.
http://www.autoacforum.com/messagevi...AR_MSGDBTABLE=
This link used to have a nice photo of what it looks like when you are adjusting the POA but I see they have taken the photo off.

Flush the condenser and evaporator out with mineral spirits ($10-$15 at your nearest big box hardware store or local hardware store).
Blow the mineral spirits out real good from both directions on each piece. And be prepared for a mess.

Replace ALL the o-rings in the system ($4.65 P/N CP3011 at Ackits.com).

Install the new expansion valve with the correct o-rings in CP 3011. Install the receiver/dryer the moment before you draw a vacuum on the system.

Fill with R134a that is still available over the counter at Wal*Mart and everywhere else. Stop at 80% of the R12 amount and then slowly adjust according to what your manifold gauges tell you.

Enjoy cheap, cool AC for another 40 years.

If you have a stash of R12 skip the POA adjustment, flush everything, replace the o-rings, vacuum, fill.

On my truck I did the R134a stuff above. In such a small space like the cab of our pickups the stock, not as efficeint as modern condenser works ok. The R12 will be much colder but again I had my system up and running last summer for a few 90 degree days and it did just fine. It didn't fog my glasses like the R12 in my 72 Chevelle does but I have yet to get out of a R134a air conditioned car and have my glasses fog.

[tkeduk8r]

quick question.... how would we pull a vacuum on the AC system at home??? is there a special tool we need to purchase????
--Mike

[leddzepp]

You would need a vacuum pump. Harbor freight sells 2 different models that go on sale regularly.

[1972RedNeck]

If I were you I'd get a compressor that was remaned in the USA.

[VWBeamer]

Originally Posted by tkeduk8r

quick question.... how would we pull a vacuum on the AC system at home??? is there a special tool we need to purchase????
--Mike

Harbor Freight makes one that works with an air compressor for about 10 bucks on sale pretty often. They have gauges also. You need a good air compressor for it to work though.

http://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html?utm_medium=cse&utm_source=googlebase&hft_adv=40010&mr:trackingCode=9E780F9E-782A-E011-B31E-001B2163195C&mr:referralID=NA

I would google for instructions. I did the AC on my 79 truck and it worked great. I would suggest running brake clean through all the hoses that you re using, and to vacuum the system down for a good while (45 minutes) to ensure it's dry. Any moisture or dirt will ruin the system.

If you don't have a good air compressor, or are going do more than a couple a year, get a vacuum pump.

http://www.harborfreight.com/25-cfm-...:referralID=NA


EDIT: I would also say get a good rebuilt compressor. The autozone/advancedAuto stuff is junk. NAPA sells a good compressor, it's going to run a lot more than the discount stuff, but it will last a lot longer. The 150 dollar compressor might make it a year.

[gcburdic]

great info folks!!!

[Michael Star]

Yes! Thank you all for the info!

[mrein3]

Whatever pump you use you want to get your closed system down to -28" to -30" Hg. What this does - if you remember you high school chemistry - is boil the moisture out of the system. You may even notice some steam coming out of the vacuum pump. Once you get your vacuum down to -28 to -30 close the valves on your gauge set and leave it alone for 30 minutes.

When you come back, if you are still at the same point on the gauges as when you left, the system is sealed properly and ready for R12 or R134a or whatever you are using. If it isn't there, don't waste your chemicals. Find the leak, fix it, suck it dry, and try it again.

The oil I used when I converted to R134a came from that ackits.com place. It contained a green dye that will make it easy to find any future leaks.

[MARKDTN]

As others have said, dryer and maybe expansion valve. I have used the POA replacement kits that make it a cycling system with good success, others have not. Might be a good time to convert to a Sanden compressor. Much more efficient. If it was me, I'd stay R12. In the grand scheme it is not much more expensive and it works. I agree, that air vacuum pump is an air hog, if you must use it I hope you have a giant compressor. You are much better off IMHO to borrow or rent a real a/c vacuum pump. Getting the air out is very important with R12 but it is critical with R134. If you don't, it won't cool well and the high side pressures will be even higher.

[leddzepp]

dont buy one of those $20 vacuum pumps that run off a compressor, unless you have a two-stage compressor at home. HF sells two different vacuum pumps that are independent and work very well. as far as a rebuilt stock ac compressor (a-6) i have NEVER had any luck with one....the front seal ALWAYS ends up leaking. i would buy a new one (pricey), a sanden, or a pro6ten from old air products (this one fits the factory ac brackets)
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