The new one should be r134 compatable, dont stress the conversion involves only changing the O rings which you will have access to anyways since you will have to remove the hoses to change the compresser. Have a shop remove the old refrigerant since it is illegal to release it into the air.
r134 should be about 2 lb
Why would you want to even consider doing this? R12 is no longer in production and as such it cost almost 4 times as much as R134. But to answer your question, use R12 in a R134 system and you will destroy the compressor as the oil is not compatible with R134 oil.
If you mix r12 with r134 air conditioning system, it will cause a high pressure in your airconditioning system and eventually damage the compressor and the evaporator. R12 is only for r12 aircon and something with r134, it can't be mix.
r134
First of all, you don't use R12. Rather, R134 which has the oil included.
Yes, it should have R134. Look on the A/C evaporator or on the compressor. it should be listed there.
R134 is used in all cars after 1992 or so.
If your vehicle is a 1994 or older is contains R12. 1995-96 It man contain R12 or R134. After 1996 it will contain R134. It is listed on a label near the compressor dryer. Engine size means nothing.
R12 It is not produced anymore. Have to covert to R134.
If the AC compressor is engaging it could be the heater control valve is stuck open. If the AC compressor is NOT engaging you probably have a problem with the controls, a sensor or the compressor.
The 1992 GMC Suburban came from the factory with R12 not R134. Unless it is has been converted to use R134 you cannot simply add R134. If it has been converted you need to have the leak fixed before adding anything. It is illegal to add refrigerant to any system without first repairing the leak. How much it will hold depends on how much leaked out.
Follow larger hose from air compressor usually by passenger side firewall near accumulator/drier