Air Conditioner Reconditioning

[midnitewarya]

Hey guys!

Finally got my engine swap, which turned into a almost total restoration, finished. Along the way I managed to get my hands on a couple of cans of liquid gold!



Here is where I am at... I have a basic knowledge of how the A/C in my 91 K5 works. Right now, I have a brand new R4 Compressor, a brand new, never installed dryer, and a new installed condenser.

Everything else is in stock condition. The lines into the evaporator were exposed while I did some sand blasting, so I figure I got some cleaning/replacement to do.

Where do I begin? I have access to an A/C vacuum pump.

 

[Blue85]

Well a charge is like 48oz, so start by finding more cans. Do you (or will you) have gauges? A vacuum pump?

First of all, keep all the new parts capped up until you're ready to install. You might as well pull the orifice tube and flush the evap before you start, and buy a new orifice. Then with all new stuff it's pretty much by the book. Look up your oil charge, pour most of it in the drier and some of it in the compressor (per specs) and assemble everything. It's good to lube all the o-rings with your oil. At this point you need to leak check by drawing a vacuum and letting it hold it. The super cheap Harbor Freight venturi pump is fine for this. Then you're ready for the real vacuum charge (or to head to a shop).

 

[longbedder]

Like Blue said, you'll need twice as much as you've got.

Honestly, if you do it right, there's really no good reason to stick with R12 anymore. You can get good cooling from R134a - just make sure the condenser is built for it (AC Delco 15-6960 is the one to have for a Blazer with R134a), the engine fan/clutch are pulling plenty of air, and the fan shroud is in good repair. That condenser is key.

 

[Big Ray]

I picked up a new vacuum pump from a guy on ebay...$55 shipped.

 

[midnitewarya]

Well a charge is like 48oz, so start by finding more cans. Do you (or will you) have gauges? A vacuum pump?

First of all, keep all the new parts capped up until you're ready to install. You might as well pull the orifice tube and flush the evap before you start, and buy a new orifice. Then with all new stuff it's pretty much by the book. Look up your oil charge, pour most of it in the drier and some of it in the compressor (per specs) and assemble everything. It's good to lube all the o-rings with your oil. At this point you need to leak check by drawing a vacuum and letting it hold it. The super cheap Harbor Freight venturi pump is fine for this. Then you're ready for the real vacuum charge (or to head to a shop).

Thanks! You mentioned filling the system with oil, is that separate from the R-12 or is the R-12 considered the oil?

Got the orifice tube on order, and a new set of O-rings.

Is there any method to flushing the system? Special fluids?

 

[Blue85]

Yes, you absolutely have to add oil. Old systems used mineral oil with R-12, but I don't think you want to be committed to R-12 long-term. I would use an Ester in a new system, as the newer oils are generally better and compatible with all the refrigerants. They do make oil charge in a pressurized and and also oil and refrigerant mixed, but that's for topping off a system that's already charged/sealed. For a new setup, it's easiest to just pour the oil from a can.

To flush, they do sell an aerosol can with a hose and rubber fitting to seal against tube openings. That's fairly convenient. You can also use mineral spirits, but you have to run a lot of compressed air through to make sure all the solvent is out (and "pop" the ends). I've used brake clean and never saw problems (it's great at evaporating clean). You shouldn't need to flush any of the new parts, though.

 

[midnitewarya]

Yes, you absolutely have to add oil. Old systems used mineral oil with R-12, but I don't think you want to be committed to R-12 long-term. I would use an Ester in a new system, as the newer oils are generally better and compatible with all the refrigerants. They do make oil charge in a pressurized and and also oil and refrigerant mixed, but that's for topping off a system that's already charged/sealed. For a new setup, it's easiest to just pour the oil from a can.

To flush, they do sell an aerosol can with a hose and rubber fitting to seal against tube openings. That's fairly convenient. You can also use mineral spirits, but you have to run a lot of compressed air through to make sure all the solvent is out (and "pop" the ends). I've used brake clean and never saw problems (it's great at evaporating clean). You shouldn't need to flush any of the new parts, though.

Thanks so much for the help. I have to flush the condenser, as the cover I made for it fell off during sandblasting. My kids stole the caps off the evaporator at some point when they were "helping". I'd like to flush just to be sure.

Do you have a link to any of the old a/c manuals?

 

[louise martin]

I really wanna thanks for such brilliant help, you have saved my money from calling an ac repair specialist.