Re: ***ac issues/help please/hot***99 wj
The best way to charge is by weight. The capacity should be on a sticker under hood. My 04 V8 HO is 27.0 oz., not sure about 4.0L
Adding R134 without knowing how much is in there is difficult and can be dangerous.
That being said, I just changed my compressor, and I charged system as follows...
1. Evacuate system. Mine was already empty due to compressor change.
2. Pull a vacuum ...pump can be rented from Autozone, or purchased from Harbor Freight..
Vacuum serves two purposes- verifies there are no leaks, and boils off any moisture in system. If system holds vacuum then there are no leaks. I left under vacuum for about an hour to be sure.
3. Add R134 to low side only (very important). I used 12 oz cans and weighed them with postal scale to ensure accuracy. You can get a partial charge with car off (compressor not running)...Once pressure equalizes between can and system you will need to start engine and turn on ac to run compressor. The compressor will draw the rest of R134 into system. Don't turn can upside down, you can slug compressor.
Besides vacuum you will need gauges, and can adapter to attach small cans to manifold gauges.