Going from summer to winter transition I lost my charge of gas due to incompetance of the service professional, twice. If you want something done right you have to do it your self. I thought it was the gaskets I had installed. So I dismantled the entire A/C system and replaced them all and the dryer again only to lose another charge.

If you changed every gasket chances are it is your service ports as was the case for me. Seems they ran their leak detector while they were still connected to the ports with the recovery system, of course it isn't going to leak like that. I even had to replace the service port on the brand new dryer I had just gotten as that was leaking.

An easy way to test the high side port is by pouring a cap full of PAG oil into the top of the port and watch with a flashlight for bubbles to form around the rubber center gasket. No bubbles, no leaks. Of course this only works with at least a partial charge in the system.

That trick doesn't work for the low side as the oil leaks out of the port too fast due to the angle. So there you should use a soapy water mix.

To replace the ports you must have the system in a discharged state. You are moraly and legally obligated to have a professional with a recovery system suck the R-134a from the system, as it is illegal to purposely vent into the atmosphere. If your gas is already gone due to the slow leak you are in the clear.

Start by replacing the schrader valve that is in your low side service port on the dryer. You may wish just to buy a replacment dryer if the system has been vented for a considerable period of time. I had just replaced my dryer yet it still leaked so I went with the EF Products 459 Hi Side / Low Side Service Port Leak Repair Kit, about $4. This also comes with replacement high and low side caps.

Using the tool provided remove the old schrader valve by unscrewing it counter clock wise. Once the valve is off of the threads you may need to use a small pair of needle nose pliers to pull it out of the rest of the way. Install one of the valves provided in the kit. Install the new valve using the tool in turning clockwise. Do not over tighten this. You want just a bit over finger tight.

The high side valve is a little more difficult. You will need to go to your local Chevy dealer's parts counter and ask for Either AC Delco Part # 15-5438 or GM Part # 52458184 it is about $17 from a dealer or $4 online.

http://www.autoacforum.com/forumimag...sidegmport.jpg

Removal of the old one requires a special octagon socket for this purpose but we aren't going to reuse the old one so it doesn't matter. Use a 16mm box wrench on the high side liquid line to hold it in place and clip on to the top section of the valve with a some vice grips. Once the seal breaks it is fairly easy to unscrew.

Coat the gasket of the new service port with some PAG oil and screw it in finger tight. Tighten the rest of the way with a small cresent wrench, do not over tighten as you don't want to round the octagon. This is aluminum.

Once done give the system a quick charge with a cheapie can of gas for leak detection, no pressure no bubbles. Do the leak detection as outlined above. If satisfied with that procede to recharge the system.

It still leaks?

You can go one of three ways for leak detection. Bubbles, UV and 'Sniffing'. All do basicly the same thing, but in completely different ways with different degrees of sensitivity.

With bubbles it is the soapy water mix and the paint brush to apply it to seals of the system. Cheap but not that effective with the super slow leaks.

For UV you need to pick up a can of UV Dye in injectable form, such as EF Products 332. After you shoot about 1/4 to 1/2 oz in remove the can, and hit the intake port with the UV Dye Cleaner/Remover EF Products 372. You also need a UV light source and if you really want to be cool a set of yellow tinted glasses, just like on CSI. This is sold in a kit but usually fairly expensive for a decent one.

It has been my experience that on a bright day you will be able to see the dye without exciting it with a UV lamp. Just look for the residue, it will look very similar to the ink left by a yellow high lighter.

Let the system run for 15 minutes or so and look around. Be sure to take off the high side service port cover. Also check the puddle of condensation from the drain tube. If it is greenish yellow like antifreeze your evaporator may be to blame.

Then there is sniffers. These generate a small amount of ozone and then look for a change in voltage from a sensor when the a halogen type gas such as refridgerant hits it. But they are expensive and usually no one will loan them out.

Turn the unit on away from the vehicle as it will use the surounding air to preset to normal. Set for maximum sensitivity. Then just poke around with the A/C system with the tip. Check under the compressor best you can as that is the most likely spots for leaks, as well as the presure sensor behind the compressor. Take readings with both the engine running and shut down. Check the evaporator by sticking the sensor in the air vent with the A/C on the lowest setting.

Hey, don't forget about the connections to the condenser, they are under the battery and require it the battery and tray to be removed from the car. You can use one of those portable jump starters to start and run the car without the main battery installed for testing purposes, just set it on the ECU.