Discussion Forum - Northstar Chevelle Club

4-door Chevelle · Super Poster

AC question

dashboard · 2K+ Club

The hose coming out of the POA valve (top of AC box) and returning to the compressor is the low pressure side.

Are you going to use R12 or convert to 134?

Chris R · 2K+ Club

If your planning to use R12. Unless you already have a few cans stockpiled, be prepared to open your wallet nice and fat.

4-door Chevelle · Super Poster

All the reading I did moved me back and forth between that one and the lower one so I was seriously lost. I did pick up a conversion kit with the compatible oil so I hope this works. I can get parts pretty much at cost at my buddys shop in Silver Bay.

Lost in the 60s · President

I've seen a number of the R12 cans at swap meets for $10 each this year. There isn't much demand for it anymore and the price has come down.

The conversion will not cool very well unless you plan to change the compressor and poa valve for the higher pressures necessaary for the r134a to be efficient. If possible, I suggest getting 4-5 cans of R12 and using that.

Low side is always the return hose. High side hose always goes to the condensor.

4-door Chevelle · Super Poster

I also searched for a diagram so I could see the flow and a label on each piece since I am not that familiar with the system.

dashboard · 2K+ Club

ac diagram.jpg

Here's a diagram showing everything you need to know.

Depending on what parts you have and parts you need; be ready to spend $500.00 to a $1000.00 to restore a system that's not worked in a while. If you do it all yourself (it's not that hard) and have all the required brackets.

You can get some nice aftermarket systems for $1000.00.

Chris R · 2K+ Club

Lost in the 60s wrote:
I've seen a number of the R12 cans at swap meets for $10 each this year. There isn't much demand for it anymore and the price has come down.
The conversion will not cool very well unless you plan to change the compressor and poa valve for the higher pressures necessaary for the r134a to be efficient. If possible, I suggest getting 4-5 cans of R12 and using that.
Low side is always the return hose. High side hose always goes to the condensor.

I would buy them all day long for 10 dollars a can. Last can I seen for sale was like 35 dollars.

Chris R · 2K+ Club

FWIW. With air conditioning systems. You cant just put the system together and put in the refrigerant and go to town from there. Any little leak and good bye to all that expensive R12 you just put in. You need to have a shop or someone with vacuum equipment evacuate the system to get out the contaminants before you charge it with refrigerant. You want to make sure there is no leaks and any contaminants are out of the system first.

Also, just cleaning everything inside the system and putting it together doesnt mean you dont need to evacuate the system either. Contaminants in an AC system are micro sized and are disolved and removed because of the negative pressure from the vacuuming process. When that crap mixes with the refrigerant, stuff gets plugged up or deterioration of parts like a compressor, evaporator or condenser will happen.

Lost in the 60s · President

Chris R wrote:
Lost in the 60s wrote:
I've seen a number of the R12 cans at swap meets for $10 each this year. There isn't much demand for it anymore and the price has come down.
The conversion will not cool very well unless you plan to change the compressor and poa valve for the higher pressures necessaary for the r134a to be efficient. If possible, I suggest getting 4-5 cans of R12 and using that.
Low side is always the return hose. High side hose always goes to the condensor.
I would buy them all day long for 10 dollars a can. Last can I seen for sale was like 35 dollars.
I passed on a few cans at an early swap meet this year for $10 each. I have a small stash already because my Pete still uses R12.
Chris is right about the evacuation process. It will detect leaks before charging too. The main thing it removes is moisture, which can kill the system.

frank · Active Member

don't know about r12 but most systems have two different size connectors so you can't do it wrong. ask pushrod what replacement refrigerant there is for r12. like a product called hot shot. i don't do to much of the service end so i'm not up on that. i do have a vacumn pump. i would have to think the high side is greater pressure the the can of r12 so it wouldn't go into system. it would want to push into can of r12. low side would be less pressure than can of r12 so it would fill system.

-- Edited by frank on Sunday 3rd of July 2011 03:22:40 PM

Lost in the 60s · President

frank wrote:
don't know about r12 but most systems have two different size connectors so you can't do it wrong. ask pushrod what replacement refrigerant there is for r12. like a product called hot shot. i don't do to much of the service end so i'm not up on that. i do have a vacuum pump.
Older systems had same size ports. Not sure when that changed but I'm pretty sure a '72 has the same size. The replacement refrigerant's used to have propane in them and are extremely dangerous. I don't suggest using anything like that. Might be something better available now.

frank · Active Member

Hot Shot
Replaces R-12, R-134a, R-401A, R-401B, R-409A, R-416A, R-420A, and R-500.

Hot Shot is the best R-12 replacement on the market—period. Here’s why.

The operating characteristics you need. Hot Shot® almost exactly duplicates the operating characteristics of R-12. Use it for low, medium, and high temperatures. Use it in autos, aircraft, and boats. Use it in air-conditioning and refrigeration systems—anywhere you used to use R-12. With Hot Shot®, there is simply no need to inventory multiple gasses.No systems modifications required. Using Hot Shot® requires no inconvenient oil changes. You’re good to go for the entire R-12 temperature range. Plus, no expensive parts retrofits are required.

Proven quality and performance. Hot Shot® is in use in thousands of vehicles and installations throughout the world. You can use it with complete confidence.

Safe and responsible. Hot Shot is classified by ASHRAE as nontoxic and nonflammable (A1) and is EPA/SNAP-accepted.

frank · Active Member

Flammable Properties:
Flash Point: No flash point Flammable Limits in Air (% by volume)
Flammable Limits in Air (% by volume) LEL: NONE (per ASTM E681)
Autoignition: 635ºC (1175ºF) UEL: NONE (per ASTM E681)
Fire and Explosion Hazards:
Cylinders may rupture under elevated temperatures and/or fire conditions. In concentrations above the recommended
exposure limit, open flame will vary in size and color. Eliminate the flame or ignition source and ventilate to disperse
the refrigerant vapors.
Hot Shot is not flammable at atmospheric pressure and temperatures below 100ºC (212ºF). Hot Shot should not exist
with air/excess oxygen at elevated pressures and high temperatures. Hot Shot can become combustible with combinations
of elevated temperatures, pressures, and oxygen, and an ignition source.
For example: Do not mix Hot Shot with air under pressure for leak detection purposes.

seems with most things there is a bad side just don't know what it is. this is copied off google not my words just copy and paste.

-- Edited by frank on Sunday 3rd of July 2011 03:40:16 PM

Lost in the 60s · President

Non-flammable would indicate no presence of propane. Seems to good to be true that it will replace all popular gasses.... I may have to do some searching for reviews now....

4-door Chevelle · Super Poster

Excellent diagram and everything confirms. Let me make a point of clarification, this is a stock, original condition, complete AC system. So, I got the retrofit oil and 2 cans of stuff in. However, it is still blowing hot air but it is important to note the clutch NEVER seems to engage at the front of the compressor.

Should I check for power at the one wire that comes to the compressor with the AC on? Knowing the system will hold 3.75 lbs and the cans contain 1 lb but the kit calls for putting in 85% of previous system capacity should I add one more can?

Lost in the 60s · President

You need to have the system running to get anymore in. The clutch MUST engage on the compressor. You may need to run a hot lead from the battery to engage the clutch to get it charged. Once charged it should function on it's own. If not, check for power at the compressor terminal. If none, find a wiring diagram and start following it back. There are several components that must work together to complete the electrical circuit. All wires must be on the high/low pressure sensors to start with. IF you have power to the clutch and it doesn't engage, the electromagnet may be bad...(pretty rare thou) or the compressor isn't grounding for some reason.

-- Edited by Lost in the 60s on Monday 4th of July 2011 11:17:09 AM

4-door Chevelle · Super Poster

That is what I was thinking Mitch so I will manually get power to the compressor and go from there. I did find a few wiring diagrams online so that will be easy to find again and print.

4-door Chevelle · Super Poster

So, I started her up and put power to the feed wire that comes from the firewall while the AC was on Max, nothing. There is a 3-wire connector with some sort of fuse/relay plugged in to it. I do not get power to either side of the plug! The connectors on either side of the plug go to the rear of the compressor and the connector for the clutch near the clutch. So, I put power at the connector near the clutch and it spun. It put a pretty good draw on the engine but did spin. I cycled it a few times just to be sure and it seemed fine. I then checked for cold air after the clutch was engaged about a full minute and there is no cold air.

So, of course I am missing something and/or may have a bad part/connection somewhere?!?

Again the question, should I add 1 more can?

It is going to be a hot 220 miles tomorrow!!! Thank God for wing windows and 360 degree air!

Lost in the 60s · President

Yes, get as much of the can in as it will take and then get the compressor running. It probably doesn't have enough in the system right now to cool. That fuse you mentioned is a thermal limiter and will blow out under stress. They are hard to find anymore. Power gets to it from a pressure switch in the system. I can't remember if it's on the high or low side. Seems to me it is on the low and not enough refridgerant will cause the switch to stay open causing the clutch to not engage. Been 30 years since I worked on these on a regular basis and the memory isn't getting any better with age...

Yes, the A6 compressors put a lot of draw on the engine but they move a LOT of refridgerant too !

dashboard · 2K+ Club

Expensive stuff, Should you calibrate the POV valve for R12 or 134A?

http://cgi.ebay.com/HOT-SHOT-R-414B-ICOR-INTERNATIONAL-10oz-Can-/400130846029

Chris R · 2K+ Club

dashboard wrote:

Expensive stuff, Should you calibrate the POV valve for R12 or 134A?

http://cgi.ebay.com/HOT-SHOT-R-414B-ICOR-INTERNATIONAL-10oz-Can-/400130846029

http://cgi.ebay.com/HOT-SHOT-R-414B-ICOR-INTERNATIONAL-10oz-Can-/400130846029#vi-desc