On 20 Jul 2005 18:30:10 -0700, "John Manner" >
wrote:

>I have a 1999 S10 Blazer 4x4 and this summer the compressor has
>developed a knock that is louder at times then other times. It still
>blows cold while driving, but only blows warm at idle. The compressor
>clutch never shuts off so I know it isn't the low-pressure switch or
>low coolant. What could be the possible causes and what should I look
>at first? I'm assuming something might be partially plugged since the
>compressor still works? Or is this what a compressor does before it
>implodes?

Chances are good that your compressor is on its last leg. Just
because the compressor never shuts off does not mean your aren't low
of refrigerant, it just means you aren't low enough to trip the
safety. In this case though it wouldn't make much sense to add more
refrigerant to a compressor that is already knocking.

Were it mine I would just drive it until the compressor finally gives
up the ghost but if/when the compressor does lock you need to get to
that switch and shut the a/c off before it cooks the belt and leaves
you stranded.

Steve B.