'99 Blazer A/C Compressor knocking, cold air while driving, but warm air at idle.

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.

I thought about that about just letting it fail, but I always heard that waiting can cause more damage to the other A/C components? Is that not the case? A/C work is about the only thing on a vehicle that I don't want to tackle, so I'm taking it into the shop for an estimate tomorrow. I'll post what I hear back for sticker-shock enjoyment.

When the compressor fails it can send schrapnel throughout the system causing you to need to replace the dryer and expansion device and thoroughly flush the system.

In this case your compressor is already knocking so there is a good chance scrapnel has already entered the system requiring a flush. The expnasion device and dryer are "must change" devices anyway so I don't really see any harm in waiting until it croaks. Other opinions may vary and four out of five dentist agree.

Steve B.

Sounds like the compressor is on its way out. You probably already have compressor shavings all over the system, so I would recommend you run it until it completely stops. Replacing a compressor is not all that difficult if you have the right tools, some books and lots of patience. I installed a new compressor recently (first time job). It was not easy, but it was very satisfying to get it working.

If it seizes you're going to be stranded, at least with a modern vehicle that runs everything off a single serpentine belt. Been there, towed that.

(In the old days, when accessories were driven by individual or subset V-belts, you could MacGyver the non-mission-critical ones through judicious use of a jackknife and perhaps a bit of belt rerrangement to make sure the fan and alternator were still going. Nowadays, everything is in the loop all the time.)

Besides, the sooner you fix the problem, the better chance you have that it *hasn't* blown chunks through the rest of the system (though replacement of the receiver/dryer is usuallly indicated anyway).

Cheers,

--Joe

It isn't his pulley bearing that is making noise, it is the compressor that is knocking. Should the compressor seize simply turn off the air and continue to drive as normal with additional sweat. Unless you are revving the heck out of the engine when it locks your just going to get a horrible squealing until you flip off the a/c (or until the belt breaks if you don't flip off the a/c).

Sounds like you had a pulley bearing go out on yours in which case the belt is going to burn off in short order.

Steve B.

Glad to hear your A/C works now. Would you please post the corrective steps to your repair in the appropriate threads you started regarding your Metro?

Toyota MDT in MO

I just got a quote of about $1100 for the repair. I don't want to put that much money in a truck that 6 years old now, so I guess I am going to do the work myself. I'm keeping the A/C off so it doesn't lock up and ruin my belt. As for the repair, getting the compressor (rebuilt) and drier are easy, but what do I do about the R-134a still in the system? Can a shop recover it for me? I really don't want to vent it. Finally, does anyone know of any good resources for this type of job?

The shop can recover the 134a for you. Your factory service manual is the best tool you can have to learn how to do the job.

Don't buy a rebuilt from your local cheapie auto parts. Best bet is a GM factory new compressor. Second best is to go over to aircondition.com and ask them who is making the best rebuilt right now.

Steve B.

I just got it recharged back in the shop. It really was that difficult of a job at all. I got a brand new Sanden compressor, new drier, and O-tube. Flushed the system, new o-rings, and bolted everything up. The only problem was I didn't realize the new compressor needed a bigger serpentine belt. Everything else when smooth.