no A\C

[bassalive]

I was kinda vague in the first decription of my problem so i'll try again. My 99 Tahoe has no cold air from the A/C. I would like to know the procedure for recharging the system with R134.

[KirkW]

The way I do it is to first find the leak. Condensers and Compressors are prime suspects.

Next, I evacuate the system with a vacuum pump (the electric pumps are far better than the venturi-style ones).

Finally, I add in the amount specified on the underhood refrigerant label. I have a 20-lb bottle of R134a and set it on a digital postage scale. But I've also had good results using several of the 14-oz cans sold in auto-parts stores.

One tip - When using the DIY kits from an auto-parts store, before snapping the fill-hose connector onto the truck's A/C, crack the valve open on the can of R134a. A few seconds of escaping gas will purge the hose of outside air. Then connect the hose to the truck.

If you have a manifold gauge set the evacuate/fill procedure is much easier.

HOWEVER, if you just want a quick'n'dirty, make it cold now I'll figure it out later, then simply get yourself a recharge can (or two) of R-134a from the auto-parts store. Add in the refrigerant while the engine and A/C is running. As you're filling it up, feel the inlet and outlet pipes that go through the firewall and lead to the evaporator. When the system is low, one pipe will feel cold, the other warm. The compressor will be cycling a lot, too (short time on, long time off) As the system fills up, both pipes will start to feel cold. The compressor will start running for longer and longer periods. When they both feel the same (cold) temp and the compressor is running almost continuously (varies with outside air temp and humidity), the system is full - stop charging. Overcharging will make the system perform poorly, as well as undercharging.

Get yourself the can with the ultraviolet leak detecting dye so if/when it leaks, you can find it.