Been looking up ways to charge my ac. Read all about the 134a conversion and all the others. I don't currently have the money to spend a few $100 on a conversion, so was looking into cheaper methods. Found envirosafe r290 which seems to have mixed results. Pretty confident in my decision to use it, but there's multiple different types and I wasn't exactly sure which one is recommended. Also, was hoping someone could give some information on it before I go blow myself up or light the car on fire

Or should I just run 134a in my r12 system and if it leaks out it leaks out or if something breaks then I have to spend the money when I have it?

Get some R12/ebay on Craigslist and be done with it. Be sure and go online and take the test for purchase license. I'm sure the seller will want to see it, before the cash.

A.c. recharge psi reading full, but nothing comes out of the valve stems if pressed. Compressor also isn't kicking on. Any idea what may cause this?

If nothing comes out of the valve stem, there is no refrigerant. No refrigerant, no pressure, no pressure, no compressor turn on.

Dont know about any r290 but the retrofit for 134a isnt that difficult and 134a wont give you any kind of adverse problems down the line. Converted my 90 corvette to 134a, works great and Im in LV. All you have to do is pull compressor out, pour out and measure any oil that comes out. Replace accumulator and do the same as comp. pour out any oil from old one. Measure total amount you get from both. Add 75% of measurement back to compressor with new PAG oil (making sure you pour it in suction side of compressor. Thats the big pipe side) Put rest in accumulator. Pressure check and while you do this step add nitrogen to high side and watch low side gauge. Should come up fairly quick, if not you must replace orifice tube which is in line going from condenser to evap. Once it holds pressure and your confident orifice is clear. Evac and recharge 10% less 134a that r12. Ideally you should replace low pressure switch install a clutch cycling switch but it will work ok without. With the clutch cycling switch it allows the evap to get down below 32* and get colder air out of the vent without freezing it up. Good Luck

I use R152a aka Keyboard Duster air myself. Get a side tap and side pierce the can. It cost me like $5.00 to recharge a vehicle and the stuff gets colder than R134a ever thought about.

Chilliewillie, I'm not sure what you mean by this. The low pressure switch does cycle the compressor. Can you explain this more?

Let me rephrase that. Its been my experience that most auto AC shops out here (LV) when converting from r12 to 134a they add a clutch cycling switch and replace LPS because 134a pressures keep evap below freezing. The CCS turns off compressor for so many seconds every minute which keeps evap defrosted enough it doesn't freeze up and blows out colder air, than r12 because its under feezing temp. Technically if you leave the r12 LPS in it would cut out compressor too soon thus not getting the most out of refrigerant and warmer discharge air temps. But it has also been my experience that in real world auto ac isnt a perfect science and conditions vary too much to get that **** about it. Since discharge air temp varies with rpm it doesnt really matter if its 38 or 48 while driving around town.

Mine gets into the 30°F range before it switches off. I usually add the late 80s cadillac thermal cycling switch on the evaporator inlet and adjust the cycling switch to cut off about 20 psi. This lets the evaporator get just below freezing and cycle off when the temperature gets too cold.