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

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?

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.

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.

On 21 Jul 2005 10:57:31 -0700, "John Manner" >
wrote:

>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.

> I don't really see any harm in waiting until it croaks.

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

On 22 Jul 2005 10:55:43 -0700, "Ad absurdum per aspera"
> wrote:

>> I don't really see any harm in waiting until it croaks.
>
>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.
>
>
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.

wrote:

> I installed a new compressor recently (first time job). It was not
> easy, but it was very satisfying to get it working.

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?

On 23 Jul 2005 13:41:48 -0700, "John Manner" >
wrote:

>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.