AC Question - New or Rebuild??

[bhammer]

Hey All,

I am thinking of replacing the AC System in my 72 LWB. It is a factory air truck. I was wondering, should I attempt to just rebuild the old system, maybe with some different hoses and such to handle R134A or buy an Old Air System? Any help would be appreciated...

Thanks in Advance

Brian

[Lemield]

I have an aftermarket add-on air unit in my CST...it works great and blows really cold. I also have factory air in my C20...it needs work but I like factory air the best. All aftermarket systems are recirculated air....factory systems are fresh air or recirculated, your choice. There are advantges/disadvantages to both....you will probably get a lot of different opinions from members of the board. Good luck with whatever you decide to do.

[70cst]

I kept mine all facory except the new R134...

[Clyde65]

OLD Air has replacement parts for your factory system, I would call them and ask some questions, also compare the cost of replacement parts vs new system.

[MARKDTN]

If it is factory, I would stay factory and rebuild it. If it didn't have it originally, I would take a hard look at aftermarket. So in your case, rebuild. I might look at converting to a cycling clutch system instead of VIR and I might look at a Sanden compressor upgrade over the original A6.

[bhammer]

Thanks for all the feedback guys. I am leaning towards rebuilding the old stock unit. I have a couple more concerns/questions. I have heard that using the old system I am stuck with using R12 due to size of hoses/compressors, etc. Is this true? Is it possible to modify the original system to accept 134A? I know that I have seen LMC carrys a modified compressor that can handle R12 and R134A, I would probably go this route. How about the hoses? Can I use the original replacement hoses? Is there anything else I would need to upgrade to get it going? If I just buy all new replacement parts from LMC can I run 134A in it as long as I use the upgraded compressor? I am trying to avoid spending the $1300 Old Air kit as I already have all the old setup. I just need to figure out what needs replacing and what will give me the best/coldest set up. Also, I wanted to retain the factory control system, I am not a fan of the Old Air control module. I apologize in advance for my lack of knowledge of AC systems, thank you.

Brian

[bhammer]

I forgot to mention, I am currently living in Las Vegas, NV. Summer is about to hit and I would love to have this thing up and running BEFORE I melt in the 115 degree heat. I am looking for the system that will run the coldest. Is R12 going to be colder than 134a? The heat is also currently INOP, I'm pretty sure I will need to replace the blower motor, hoses, compressor, drier, receiver, and the control module probably needs reworking. The levers on it are all stiff and stuck and don't slide well. Thanks again fellow truckers...

Brian

[leddzepp]

Originally Posted by Clyde65

OLD Air has replacement parts for your factory system, I would call them and ask some questions, also compare the cost of replacement parts vs new system.

I agree.

Originally Posted by MARKDTN

If it is factory, I would stay factory and rebuild it. If it didn't have it originally, I would take a hard look at aftermarket. So in your case, rebuild. I might look at converting to a cycling clutch system instead of VIR and I might look at a Sanden compressor upgrade over the original A6.

I agree with upgrading the compressor. However, I recommend an A/10 replacement compressor from Old Air products. It is NEW not rebuilt. It bolts directly to the factory brackets. A rebuilt A/6 will leak at the front seal. I know, I went through 4 of them. The A/10 did not leak. They run $350-$400. Expensive, but the last New (NOS) A/6 I sourced was $800. You can run R-12 or R-134 through it. I would keep the factory AC system if it is all present and intact.

[leddzepp]

Originally Posted by bhammer

I forgot to mention, I am currently living in Las Vegas, NV. Summer is about to hit and I would love to have this thing up and running BEFORE I melt in the 115 degree heat. I am looking for the system that will run the coldest. Is R12 going to be colder than 134a? The heat is also currently INOP, I'm pretty sure I will need to replace the blower motor, hoses, compressor, drier, receiver, and the control module probably needs reworking. The levers on it are all stiff and stuck and don't slide well. Thanks again fellow truckers...

Brian

R-12 is very expensive, a lot of shops don't even carry it anymore. You can't buy it off the shelf. If the system is properly converted, R-134 works just as well, I recommend it. I live in SoCal heat, and I went with 134 when I put in the new compressor. As long as the system is flushed and POA valve adjusted properly, you will have no problems. I also recommend you have a shop do this for you the first time, unless you have done it before and have the proper tools (vacuum pump, gauges, etc)

[mrein3]

I would definately use the stock system. Stock A6 compressors last a long time. I'm not sure on this A/10 replacement but I'm sure it works fine too.

The most important thing you need to do is adjust your POA to work with R134a.
Click your way over to:
http://www.autoacforum.com/messagevi...&threadid=7567
and follow the instructions about 1/3rd of the way down to make your system work with R134a.

Then flush out everything real good. Buy new R134a compatible oil. Get your R134a over the counter at Wal*Mart or similar. Buy all new o-rings and a new receiver/dryer (you have to buy a new receiver/dryer no matter what way you go). Use the $1200 - $1500 you're going to save over not putting in an aftermarket system to purchase a vacuum pump. Then do all the work yourself. With the purchase of the pump you'll be $1000 ahead of the guys that installed aftermarket.

You'll be way ahead of the game because if your A6 compressor does go out or something else happens, you still have your new vacuum pump you purchased with the money you saved and now can service the system yourself.

[70cst]

Looks like great info ...

[Dark Knight]

I recently did this, except I pieced together a stock system instead of having it all there. I paid $55.55 for everything. Go eBay. First off, R134a will be about the same temperature as a R12 system. You won't even notice a difference. There are several companies that offer a POA valve eliminator kit. I highly recommend this. That way, you won't have to have the old one adjusted, plus they've been known to fail. All the kit does, is turn the normally on compressor to a cycling clutch setup, like a newer car. As for hoses, get a barrier type hose set from LMC that is set up for 134a. I would also replace the short high-side hose, expansion valve, and dryer. Flush the system with A/C flush too (but only the hard lines, evaporator coil, and condenser). Clean the fins on the evaporator too. A stock replacement A6 compressor will work just fine. Re-assemble with new o-rings, add oil (Ester), pull a vacuum, and add freon. Then you'll be good to go! I'll have to look up how much oil it takes though. I believe it's somewhere between 8-12 oz. PM me if you have any questions.

[bhammer]

Thanks for all the info guys!! You've been a great help.

So here is where I am at with everything. I currently have all of the stock components in the truck. It has not worked since I bought the truck 2 years ago and according to the PO told me it hasn't worked for 10+ years. I am not exactly sure where to start with it. I don't know what is bad and what is good. I did have my local mechanic hook up his AC machine to it and charged the system revealing a leak SOMEWHERE, lol. That's about as far as I went. He recommended an aftermarket system. I'd rather stick with the factory setup for a few reasons, one being that I can probably get it running with only purchasing a few new components rather than the whole she-bang. Also, it will work just as well as an aftermarket system from what I have heard. I know that the compressor is locked up, I will be replacing that. I am also planning on putting in a new evaporator core, receiver, drier, and hoses. Sorry for being ignorant on this, but what is the POA valve? Do I need to replace the heater core? Do I need to buy a whole new wiring harness? I am a very mechanical guy and have done a lot of the mechanical work on the motor, etc. However I know nothing about AC systems and don't want to get halfway through and screw up a bunch of new parts. I work for O'Reillys Auto Parts and I caution people all the time about putting in those do-it-yourself cans of refrigerant. I know putting in way too much will blow your o-rings and waste your system in no time. You guys have already been a great help, thanks again. I'm just lost as to where to start. I have the money set aside but am not sure where to begin. I am most likely going to have an AC shop here in town do the work. Prior to me posting this I had no idea there were things like a POA bypass kit, etc.

Brian

[mrein3]

You need to find the leak.
It could be something simple like an o-ring.

Being that you need a new compressor, you might want to look into the a10 replacement that is available.

In your position, this is what I would do - at home.

Get a vacuum pump.
I was just in Harbor Fright yesterday afternoon. They have a vacuum pump for $110. I was going to do some investigation work today and see if it is strong enough to pull a deep enough vacuum for an automobile AC system.

Get that a10 replacement compressor.

Follow the link I posted and adjust your POA.
The POA is mounted on the outboard side of the HVAC box under the hood. Open the hood, walk over to the RF fender, bend over with your ear next to the hood hinge. The POA is touching your nose.

Flush out all the remaining components with AC flush. Skip your old compressor and receiver/dryer - they are going away.

Click around on the ACkits website and purchase a new set of o-rings for your system. Replace them all.

Get a new receiver/dryer from ACkits or since you work at O'Reillys Auto Parts get one there - but wait until you're ready to charge your system. The receiver/dryer contains a dessicant that removes moisture from your system. It should be exposed to the atmosphere as long as it takes you to screw the hard lines into either side of it.

Add oil since you flushed it all out. You need at least 10 ounces. I believe 1972 GM manuals stated 11 ounces. Make sure you put in at least 10. You want 6 in the compressor. Dump the rest in the receiver/dryer.

Button everything up and pull a vacuum. Consult the shop manual but if memory serves you want -28" of Hg. At that pressure all the water in your system will boil and get sucked out with the vacuum pump.

When you get to -28", close up the valves on your manifold gauge set and go away for 30 minutes. When you come back if you still have -28" you are ready to dump in R134a.

After all this use it. If it stops working you have all the tools to fix it yourself. Leaks are usually found by finding oil on one of the components. If its a hose replace it. If its an o-ring replace it and make sure you tighten the connection good. Pull a vacuum, add R134a and try it again.

[bhammer]

Hey,

Thanks a bunch for that.. I am going to be attempting it as soon as the compressor I ordered comes in. I have a better understanding and read through that forum you linked to and it has a bunch of good info. I'll keep you posted on how things go.

Brian