a/c troubles

[dieseldaver]

I had a little problem with my a/c. A rock went through the condenser a couple of years ago, and I finally got around to putting a new one in. I had it charged up, but it is only blowing cool air, not cold. Talking with the mechanic that filled it, he said everything seemed normal. Did all the feel this, feel that tests and all is good. He mentioned that quite often the rad-like part inside the cab (I forgot the name of it) gets plugged up. I figured I could check it out, but once I got in there, I found it's darned near impossible to get at it. I pulled the fan out, and can feel some bits of leaves with my fingertips. I ripped apart half the dash, but I can't get the plastic box that contains the rad-like thing to move, let alone open. Anybody know how to get at it? It's a 1994 Sierra, 4x4, extended cab.

[HowieE]

You are right, it is almost impossible to get the evaporator out. You would have to removwe the bottom shell that houses the heater core, remove the heater core then remove the shell the houses the evaporator.
If your AC worked before the rock I do not thing a plugged evaporator is your problem. If the system was open for any length of time and not cleaned you may have a plugged expansion valve scree. First check to see if the AC is charged enough to work and the screens are passing gas. With the truck running and turning about 1500 rpm the suction line, the larger one coming back to the compressor, should be cold to the touch and should even form condinsate if there is any hymidity. If this is not the case have someone put a set of guages on the system and check it out. You may only need to have the system topped off before you go any futher.
Good Luck

[dieseldaver]

It never really worked properly before the rock. I did get it fully charged just yesterday, so it doesn't need a top up, and that tube you mentioned was cleaned out. All the tubes feel fine like you mentioned.

[GARY PAGE]

HOLD ON BEFORE YOU TEAR INTO THAT THING. I HOPE YOU HAVE THE SHOP MANUALS. RUN A PERFROMANCE TEST ON THE SYSTEM PRIOR TO TEARING IN THE DASH BOARD. TAKE A THERM AND PER THE TABLE IN THE MANUAL BASED ON REL HUMIDITY AND TEMP MEASURE THE TEMP OF THE AIR COMING OUT OF THE VENTS. MAKE SURE THAT IT MEETS MINIMUM SPEC BEFORE TEARING IN THE BOX. IF IT DOESN'T IT MEANS TWO THINGS.

1) THE SYSTEM IS NOT CHARGED CORRECTLY
2) THE AIR MIX VALVE IS NOT WORKING CORRECTL AND YOU ARE MIXING HEAT WITH THE AC.

EVEN WITH A CLOGGED EVAPORATOR CORE IT GET COLD AND WILL MEET SPEC AT THE VENTS, IT JUST DOEN'T PROVIDE THE VOLUME OF AIR YOU ARE LOOKING FOR. IF THE ABOVE TESTS ARE GOOD THEN MAYBE YOU HAVE TO PROCEED WITH A MASSIVE PROJECT, HOPE YOU HAVE A GOOD BACK!


THATS AN R12 SYSTEM RIGHT?

[dieseldaver]

Nope, not the R12, it's the newer stuff. I gave up on pulling the dash apart to get that out. I was able to blow air through that rad-like thing inside the cab enough to get a bunch of pine needles and dirt out, but it seems like it wasn't the culprit. I'm taking it to a guy who specializes in a/c stuff, so hopefully he'll have a better idea of what's going on. I'm starting holidays, so hopefully he'll have it running by the time I'm back in two weeks. Thanks for the ideas.