AC Recharging question

Okay, I've got an '82 El Camino, which all of it's refrigerant leaked out of. I've sinced fixed the leak, and am looking to recharge the system. I bought one of those typical cans of R134a and got to work.

It says to attatch to the low-end port, between the compressor and the vaporizer. Which, in my case, happens to be sticking out of the side of my Accumulator/drier.

I started the car like it said, and started filling. THe pressure started to go up, and the compressor began to run... then the pressure tapered off, and the compressor stopped. And the pressure began to rise, the compressor started, pressure dropped, and it stopped.

Leaving it turned off, the pressure needle is up in the yellow, signifying it is too full.. but I start my car, and the same thing happens again...

So which is it, is it too full? Or is it still empty? Am I doing something horribly wrong?

I am assuming that your car has its original A/C system and has not been retro-fitted...

In 1982 cars did not use R134a as freon, they still used R12 which you can no longer buy here in the United Stated without the proper refrigerant license. Take your car to a shop that works on A/C systems tell them what you did and pay them to fix it, your A/C will not work correctly until you do.

I retrofitted it myself... the system had been completely gutted by the previous owner, so I had to replace, and install everything myself. I went ahead and bought R134a compatible parts.

Did you hook a vacuum pump up to it and suck all the air out of all the lines before you put the freon in it?

Find a pressure/temperature chart for R134a online and then hook a set of gauges up to the lines, the pressure in the low/high sides should closely match whatever is on the pressure/temp. chart for a given temp., if the pressure is low you need put more freon in, if the pressure is too high you would need to remove some.

There is a really good chart at: http://www.hantech.com/support/documents/HTCPressureTemperatureChart.pdf

I had orriginally brought it to a mechanic, and had them charge the system, because I lacked the tools necessary to do so for the first time. After a month however, almost all of it had leaked out.

So, there shouldn't be any air in the system... right? Just very little refrigerant.

A gauge game with the filling canister... that's where the source of my problem is. Its reading keeps varrying, and I'm not sure which one is right.

Off, it says it's dangerously over-presurized. Turn it on, and the pressure bounces back and forth between too low, and too full... causing the compressor to turn on, pressure drops, and it cuts off. Pressure Rises, compressor turns on, pressure falls, compressor cuts out....

Maybe your system is operating as designed. Does your gauge show the pressure in numbers, or just low, medium and high? A typical GM cycling clutch setup will cycle the compressor off and on during operation. When the low side pressure (the port you've connected to between the compressor and evaporator) drops to roughly 30 psi, the compressor will turn off to prevent the evaporator from freezing up. When the low side pressure starts to go back up again (this is normal as the pressures are equalizing with the compressor off- it would make more sense if you could see the correlation between the high and low sides with a gauge set connected) it will turn the compressor on at about 45 psi, and the cycle will begin all over again.
Now, if the compressor is cycling on and off really quickly and your ambient temperature is in the neighborhood of 70 degrees F, i would say that the system is still low. It would help to have a pressure/temperature chart and some gauges, as was already mentioned in a post above. Have you verified that the air coming out of the vents is cool?

There we go, now that's something more usefull. :D

The compressor turning on and off takes about a second, maybe two each time it kicks in, then shuts off after about the same amount of time, rinse and repeat.

And I checked, the air is still very much warm... perhaps 1 or 2 degrees cooler than ambient... really not doing anything at the moment.

It does have numbers, as well as the color-coded system. It's a little late for me to check atm, but I'll get the exact readings tomorrow if you think it would help.

It kinda makes sense to me that it would act like this. But I wanted to be sure before i started pumping another can of refrigerant in, and blew up my compressor, or a gasket or something.

Check the pressure/temp chart at that link I posted, at a given temp. the pressure should equal what the pressure is on the chart, if the pressure is low you need to add more freon, if the pressure is too high you have too much in. Either one will cause it not blow cold air.

Torch... I appreciate the effort you're putting in... but did you even read my posts?

I know what too full is, and what too empty is... the problem is, my gauge is giving sparatic, eratic, and a several other 'ic readings.

I was, and still am pretty sure it needs more. But I wanted some confirmation before I pumped too much in there, and hurt something. But then, I suppose I can't hurt anything by obver-filling it if it's not running... after all the high-pressure switch would cut off the system. And if the can can keep that kinda pressure inside of it, then the rest of the system should be able to as well.

Was the system empty before you started charging?
How much /how many lbs/oz. have you added?
There should be a tag on system as to how much it takes to fill it.
Some of the older R-12 systems take 3-4 lbs of gas to fill them.

But you can not properly recharge with a wall mart one gauge death kit.
And a lot of the death kits contain stop leak and fit all ac oil.
You need a AC recharge gauge set with a low and high gauge.

On a retro fit kit or change over from R-12 to R-134 you need to cut the charge around 10-15 percent to hold down high pressure.
If you can post back your low and high side pressure readings at idle and at 2K rpm with compressor running or jumped and running.
MT

Good call, MT-2500. i agree. the sealer that comes in those kits IS death.