Thoughts on my r134a pressure?

[1 Wild R/T]

well yea you could as long as you don’t plan to drive it anywhere and just sit and idle it. Otherwise seems like a waste of time to me.

Oh, he's right, you can... But I challenger you to find an Auto A/C shop that does... Unless the guy at the shop worked in household or industrial A/C he was taught to do it with pressure gauges.... In the automotive world we don't look at Subcooling,Super Heat or Super Fly for that matter...

 

[Cranky]

Man, I'm going to die because I've been doing it wrong all my life!! My 95 Dakota has a slow leak and will go down a can in about a year and a half. According to the data tag, it holds 2 lbs. It still cools pretty well but the firewall/blend doors leak probably due to an ill attempt to replace the evap core at a 'professional' shop so if it's been sitting in the sun, it takes awhile to cool down while driving. The truck was still in warranty back then and have to idea why dad didn't take it to the dealer but that's some of things my dad was was doing in his mid 70's. I got the truck about a year later (98) when he passed on. My 96 Dakota puts out 40 degrees in the center register and the firewall etc are fine. The only other vehicle that I owned and cooled this good was a 70 Challenger!

 

[66chargerpat]

I when back and watched the vid. I never seen a clutch cycle like that. There's something else going on. Please everyone, watch the vid. That double cycle is strange. Almost like two different thing are controlling the clutch.

 

[dryheat]

Either low on freon or pressure switch screwed up.

^^^ THIS ^^^

Also ... check the wiring for loose / sporadic connections from the thermostat.

Which VA system system did you install?

 

[toolmanmike]

Either low on freon or pressure switch screwed up.

This. The low pressure switch is on it's threshold. That's why the clutch is cycling like that. I always introduce freon until the clutch stays engaged then let it stabilize before I add more.

 

[JerseyJoe]

Sorry guys, it's raining here and I had to pick up a new tap for these new fangled self sealing cans.
Had to do it in the garage and I don't have a big fan but I'm happy with it until I get it out on the road with some realistic ambient temps. The compressor is not cycling like it was yesterday and it is definitely cooling well inside, I never had condensation on the glass before. Vent temp was 45 degrees. It might have continued down but it was idling/roasting in the garage and I shut it down. Thanks everybody for the input!
It's the "Sure fit" Vintage Air kit for the 69-70 B Bodies.

 

[Beekeeper]

Heck yea pressures are spot on now! Now ride around in the miserable heat be cool as a cucumber

 

[69L48Z27]

That looks like you got it!

 

[JerseyJoe]

Thanks man! Figure's today it had to rain

 

[Ranger16]

I had to pick up a new tap for these new fangled self sealing cans.

Funny you mention that. You would not believe what I recently went through and how long it took me to figure out that they changed them.

 

[RJRENTON]

Does this system make any mention of how many oz it should have for the intended vehicle? If you are using 12 oz cans to fill, figure in that you are going to lose at least 2 oz per can through the hoses and gauges and since the system won't really pull much once the can is almost empty, there will also be about an oz still left over in the can.

IF, during the charging process, if you INVERT the can, you will exreact ALL the refrigerant as a liquid, which by the time it gets thru the hoses and chargjng manifold, it will have turned to a gas. Plus the vapor pressure in the can will remain high. If extracting gas, the can's vapor pressure will drop causing much longer charge times, due to pressure drop caused by evaporation.
BOB RENTON

 

[Cranky]

IF, during the charging process, if you INVERT the can, you will exreact ALL the refrigerant as a liquid, which by the time it gets thru the hoses and chargjng manifold, it will have turned to a gas. Plus the vapor pressure in the can will remain high. If extracting gas, the can's vapor pressure will drop causing much longer charge times, due to pressure drop caused by evaporation.
BOB RENTON

Think I've done that before......and the can still had some left but wasn't much.

 

[toolmanmike]

IF, during the charging process, if you INVERT the can, you will extract ALL the refrigerant as a liquid, which by the time it gets thru the hoses and chargjng manifold, it will have turned to a gas. Plus the vapor pressure in the can will remain high. If extracting gas, the can's vapor pressure will drop causing much longer charge times, due to pressure drop caused by evaporation.
BOB RENTON

I always charge through the low side using liquid. Turn the keg over and let her flow. I do that for R12 as well.

 

[RJRENTON]

Sorry guys, it's raining here and I had to pick up a new tap for these new fangled self sealing cans.
Had to do it in the garage and I don't have a big fan but I'm happy with it until I get it out on the road with some realistic ambient temps. The compressor is not cycling like it was yesterday and it is definitely cooling well inside, I never had condensation on the glass before. Vent temp was 45 degrees. It might have continued down but it was idling/roasting in the garage and I shut it down. Thanks everybody for the input!
It's the "Sure fit" Vintage Air kit for the 69-70 B Bodies.

View attachment 979346 View attachment 979347

I guess it depends on your philosophy regarding charging. I all my years in dealing with automotive air conditioning systems, I almost NEVER connect to the high side pressure port, taking all readings at the compressor's inlet or low pressure connection port of the system, usually located on the suction dryer/accumulator, not to be confused with the liquid line dryer as used on the vintage Mopar A/C systems.
If, when changing with a refrigerant manifold with 2 gauges, oberve the low pressure gauge's pressure reading for the gas being charged. The outer scale is the pressure. While sighting along the needle, observe the TEMPERATURE of the gas at the pressure reading, of the gas being measured (usually there are several different gases listed). This is the saturated gas temperature, including the gas's superheat temperature which is very close to the air temp off the evaporator at the center outlet of the dash. The amount of super heat added is usually controlled by the refrigerant's liquid metering orifice OR a thermostatic expansion valve (TXV) a variable refrigerant metering device OR the evaporator's pressure cycling switch, as in GM's CCOT system (Cycling Clutch Orifice Tube). Superheat is a thermodynamic term that permits the cold refrigerant gas to absorb more heat after undergoing the liquid to gas phase change. Later, as more knowledge of how R-134A operates and cools, different systems were introduced. The variable displacement axial flow compressor is probably the best suited for most automotive applications allowing for large temperature variations of both evaporator and condenser conditions....maximum displacement for rapid cooling and minimum displacement for low temperature operation in winter conditions.
Which system is best and which charging method is best is a matter of personal preference. Just my opinion of course.
BOB RENTON

 

[1 Wild R/T]

If the low side fitting is a reasonable distance from the compressor enough to allow the liquid to expand & change state I like to charge with liquid, but some compressors have the fittings right at the compressor like in the picture below... If you hit the compressor with liquid while running it can destroy the compressor, sometimes it damages the reeds but it can also displace the swash plate.....

 

[RJRENTON]

If the low side fitting is a reasonable distance from the compressor enough to allow the liquid to expand & change state I like to charge with liquid, but some compressors have the fittings right at the compressor like in the picture below... If you hit the compressor with liquid while running it can destroy the compressor, sometimes it damages the reeds but it can also displace the swash plate.....

View attachment 979921

I'm aware of the consequences or the potential possibilities of damage. There is an additional component that can be added to a charging manifold (available thru W.W.GRAINGER) that permits liquid charging thru the inlet port, by metering the liquid refrigerant at a controlled rate, to prevent liquid slugging. There is an old expression: "you cannot compress a liquid", definitely applies. The idea of liquid charging, with the right equipment, and with prudence, especially if adding refrigerant oil is both safe for the equipment and installer. Again, due to the length of the hoses and the insertion point, the liquid to gas phase change will have occured before the compressor would see any damage.
BOB RENTON
FYI...
Imperial Kwik Charger Liquid Low Side Charger
9 reviews

Part Number:535-C

IN STOCK
Kwik Charger Liquid Low Side Charger 1/4" female inlet, 1/4" male outlet
The Kwik Charge® charging unit accepts liquid refrigerant from the cylinder and discharges into low side of the system. Charging rate is up to eight times faster than vapor charging. In addition, liquid charging is required when using R-410A and other blended refrigerants.

• Attach the Kwik Charge device to the low side of the charging manifold.
• Charging hose is connected from Kwik Charge device outlet to low side of refrigeration system.
• Internal metering element reduces liquid flow to a level below capacity of compressor, assuring a safe, fast charge without endangering the compressor.
• A built-in ball check valve automatically opens when drawing a vacuum to assure rapid, unrestricted evacuation.
• Can be used with all fluorinated hydrocarbon refrigerant systems.

RJR

 

[Demonic]

Pfff. You don't need to spent the money on that. If you're concerned about liquid damage when you charge, just throttle the low side valve - with a little experience you can feel the liquid flash off in you manifold set.

The EPR valves in the V2 compressors prevented this with R12. Their restriction, in addition to regulating the evaporator pressure, also insured that if any liquid did not change state in event of low load, would flash off across the EPR. I had always hoped someone would design a 134a EPR valve. Then you could maintain a 36* evaporator - and not have to worry about dropping to 32* evaporator.

 

[JerseyJoe]

Gentlemen I have an update. I wasn't able to drive the car until today, and while the refrigerant pressures are still great the compressor was clicking on and off again, a lot. But when I jump the terminals on the switch at the dryer the compressor runs constantly (as it should) and the cabin begins cooling off.
Unless I'm on the wrong track, I'm going to try the switch next, It looks like a regular parts store switch, nothing special.

 

[toolmanmike]

Gentlemen I have an update. I wasn't able to drive the car until today, and while the refrigerant pressures are still great the compressor was clicking on and off again, a lot. But when I jump the terminals on the switch at the dryer the compressor runs constantly (as it should) and the cabin begins cooling off.
Unless I'm on the wrong track, I'm going to try the switch next, It looks like a regular parts store switch, nothing special.

View attachment 980590

You may loose all your freon when you unscrew the switch. That's a low pressure switch. I bet you have a leak. Run the system to pressurize it and test all the hoses, fittings and service valves with soapy water.

 

[JerseyJoe]

You may loose all your freon when you unscrew the switch. That's a low pressure switch. I bet you have a leak. Run the system to pressurize it and test all the hoses, fittings and service valves with soapy water.

Sorry I didn't mention I did drive it for about 20 minutes first, then put the gauges on it. I can check for leaks again but I'm pretty sure at 55 psi while running (it's 95 degrees today) the switch should function properly. It was emptied and recharged 3 days ago.