AC Problems

I'm sure that this has been discussed before and I did a search on this forum and read many of the posts - but there is always hope that someone has been through a similar situation and has the exact answer.

I have a 98 Classic with a Sanden compressor. I turned on the AC the other day for the first time since last summer. It blew just warm air. I have noticed that for quite some time there is a whirring noise which is preceded by a good click/snap. This can be heard in the cabin while at idle. The whirring cycles for 3-4 secs, clicks/snaps and is gone for off about the same. Today I popped the hood and the noise is coming from the compressor. I started the vehicle and heard this noise. Then I went for a drive and the AC almost seemed to be working - not really cold but not warm either. The air does have that "refrigerated" smell to it. I turned the vehicle off for about 20 minutes. On restart the sound was gone and the AC blew very warm air. Suggestions? Does this sound like classic low coolant symptoms? If so, does it hurt the compressor running it with low coolant?

On another matter the vehicle was showing a Check Engine code for a few days but before I got around to having it read, it went away. Do codes just go away or do they only disappear when the problem goes away as well? I am thinking it was just a gas cap issue (not tight enough) and that it clear itself out after a number of restarts.

Any help or suggestions would be greatly appreciated.

Sean D

That clicking is the compressor clutch cycling, if it does it more than 5x in a minute then the R134 is low and *sometimes* you can just go buy the hose and a small can of coolant. Find a can of dupont w/dye in it. If you were to rate checking the oil, filling up with gas and washing the windshield as a 1 difficulty rating topping off a AC system is a 1 too.
Back out T fitting on hose connector, its got a pointy end for punching a hole in the can.
Screw hose to can
Start engine
Turn A/C on cold and high
Remove schrader valve cap right by the PDC
Snap hose on to schrader valve
Screw T handle down into can to puncture it, then back the T handle out.
Can will start to get cold as the system sucks it in. I turn the can upside down so it pulls liquid instead of gas, fills it faster.
Once can is empty unsnap schrader valve connection and put cap back on.
Unscrew can from hose and throw away can.
Done
As for codes, some will reset after a restart, after several restarts, some will require an OBDII tool to reset and clear the code, depends on the code. OBDII reader is about $150 and is a VERY handy tool to have in your box. I've had one that comes on every once in a while if I coast down a very steep hill for a long distance, that one takes 5 cold cycles to clear or 3 seconds to hookup my acctron scan tool and clear it myself. Being able to see the code is very settling, lets you know if it's a bad one or not.

Rich:

Thanks for the very informative AND prompt response. I will give recharging the system a whir myself - especially with your detailed instructions.

Would the clutch only be cycling when the engine is cool(er) or should it do it all the time at idle?

As for the code, I've exprerienced no driveability issues whatsoever. I always though that the check engine light would always remain on as long as problem was being detected - sort of as a permanent reminder to get it checked. Therefore, when my engine light went away, I assumed the problem had rectified itself. Is this not true?

Sean