I have a bunch of r12 freeon i want to use to recharge my ac. I cant find the fill valve on the low pressure end. Does anyone know where it is?

Moving to Tech/General Engine.....................

The side of the accumulator/dryer

Thats the high pressure side though, my pressure gauge says theres way too much pressure in there, even though half my freeon is gone

that is the low pressure side. the accumulater ,drier

That's the low pressure side.

With the compressor not running, if there's any significant amount of Freon in the system at all, you will read about 80-100 psi there, depending on the temp of everything.

Disconnect the plug right next to that, with the 2 terminals with green wires, and short the pins of the plug together. Then turn on the air. The compressor should come on, and the pressure at that schrader valve should drop ALOT. If the system were full, you'd see it drop slowly and stabilize at around 35-40 psi depending on engine RPM and ambient temp. If you see the pressure go below about 30, it's substantially low, and needs at least 2 cans.

The high pressure side is on the smaller line somewhere; mine is below the coolant bottle. It takes a special fitting to hook a gauge there. If you don't know what you're doing, leave it alone. Just pay attention to the low side.

Add a can of Freon, and see what the low side pressure goes to. Keep adding it until you see about 40 psi at the low pressure port with the thing set to normal air, highest speed blower, engine RPM about 2000-2200. When you've got it like that, you should be able to take your jumper out of the plug with the green wires and hook it back up, and it shoulfd work normally.

I was having problems with my ac pressure being too high! After adding a couple of cans of R-134A during my retrofit process my dad and I decided to check the pressure. It was high so we thought we had a big problem. Little did we know that the pressure goes up once the car isn't running. Your post really helped and the ac charge process will definitely be over tomorrow when we finish adding more R-134A

Once again Thirdgen has saved me!

Where did you get a bunch of R12 from?

in a barn. Id imagine the stuff has a shelf life. I havent had a chance to refill the system yet to tell. Transmission probs. My cousin in ohio has a 30 gal keg of the stuff. He was licensed to capture and recharge systems in the 70s. The ones i found in the barn were little cans that somebody bought at kmart for 78 cents.

The shelf life on that stuff is not an issue. It's pretty permanent.

My wife used to work at a plant where they canned it..... I remember buying it by the pallet for about 72 cents a can, when I worked at a place that (among other things) installed air conditioners in new cars for dealers.

I still have the license. Still have a recovery machine. Use it every now and then.

Wow, at .72 cents I could have made millions.

Forget building cars, i need to build a time machine.

40 Psi at 2K rpm is overcharged, and will negatively impact cooling performance. The lower your low side pressure is, the colder the air can get. At 40 Psi, R12 evaporates at about 45 degrees F. http://www.delanet.com/~pparish/pt-table.htm but at 28.5 Psi, R12 evaporates at 28.5 degrees F. The temperature of your evaporator core is directly related to your low side pressure, and the temperature of your air vents is directly related to your evaporator core temperature.

The difference is in your engine speed. At idle, with blower on high, a properly charged system may hit 40 on the low side, but as soon as the engine is reved up (as little as 1200-1500) it should pull down near 30.

You shouldn't need to jump the clutch cycling switch, unless your system is completely empty.

If you don't have a proper set of gauges, a quick way to check your system charge is to watch the compressor cycle rate. On an 80 degree day, with the blower on high, and the engine idling, if the compressor cycles on and off more twice a minute, it may be low. If it doesn't cycle at all, it may be overcharged. Ambient temperature has a lot to do with it. Hotter weather will cause the compressor to cycle less, and colder weather will cause the compressor to cycle more.