AC compressor diagnosis

[KeithG]

I've got a 97 Camry with an AC system that doesn't work. Its worked without fail since 97. Pressing the AC control button causes the compressor to turn for a very brief period of time followed by the apparent re-engagement of the compressor clutch. The AC indicator then starts blinking.

So I got some gauges yesterday and there 70 psi on both sides.

The belt seems fine, but I do smell a hot rubber smell from it after the compressor stops.

I'd love a few tips on what else I should do to diagnose the issue. I plan to get it evacuated before I tear into the parts, (if necessary, of course.)

I've read from mrtech2 (sp?) that shorting compressor somehow to force it on is a common thing to do, but I don't know if its appropriate in my case.

Thanks. Good links are appreciated too.

 

[shanneba]

http://basicautomaintenanceandrepair.blogspot.com/2009/04/auto-ac-repair-101ac-troubleshooting.html

http://basicautomaintenanceandrepair.blogspot.com/2009/04/auto-ac-repairr-134-pressure-ranges.html

 

[Chris142]

What are the guage readings when it's engaged? Whats the ambiemt temp?

 

[KeithG]

The gauges don't move when it engages. And, it only engages for less then a second.

Last night at about 75F both gauges were at 70 PSI

 

[KeithG]

I've also found this helpful:
http://www.aa1car.com/library/ac98.htm

So I'm narrowing down the possibilities to:
Blockage
failing compressor
clutch issue

 

[rshaw125]

Clutch / bearing worn out? Usually you can remove the clutch and bearing assembly and re-install a new one without messing with the freon. Not uncommon.

 

[KeithG]

I'm getting a little more certain about what I know and don't know about these things after reading more posts. My issue seems similar to this post:

http://www.bobistheoilguy.com/forums/ubb...true#Post873966

I'll test the clutch voltage and try adding some sauce.

More info. tonight...

 

[KeithG]

I was able to get the compressor going by shorting the pressure switch. The gauges went to 0 and 90 PSI and its about 80F today. I only ran the compressor for 30 seconds or so for fear of damage.

Now, how can I assess the situation? Am I empty and leaking? Or am I low and possibly not leaking?

If I'm empty I'd be apt to replace o-rings ,seals, and accumulator before vaccuum testing for further leaks. Right?

If I'm only low should I even attempt a recharge?

Thanks for the tips so far, hopefully you all have a few more in ya'

 

[scurvy]

Originally Posted By: KeithG
I was able to get the compressor going by shorting the pressure switch. The gauges went to 0 and 90 PSI and its about 80F today.


If your low side gauge went to 0 psig & the high side gauge went to 90 psig, you may be undercharged or have a system blockage.

Let the system equilibrate and measure the low & high side pressures (they should be the same). Compare them to this chart after measuring the system temperature (infrared thermometer helps) to see if the overall amount of R134a is correct.

If your earlier statement of 'both sides at 70 psig' was correct and the system was at 80°F, it is undercharged as it should be at 87.6 psig at that temperature.

 

[KeithG]

So I added about half a can of R134a and the pressure increased to the correct range. I replugged the pressure sensor and took the car for a drive. The system seemed to be working. Then I noticed the noise at higher rpms. The compressor or clutch is making a howling/ grinding noise.

Even though I don't know how to diagnose it, its probably a safe bet to plan an compressor & clutch replacement. Yes?

Any chance the compressor needs a little oil? Or would that indicate a leaky compressor that needs replacement anyway?

Thanks.

 

[mechtech2]

70 at 75 F ambient after a good long sit should be correct.
But not if there was any heat in the engine compartment!

I never saw 0 and 90 readings - this is unanswerable.
Being low on fluid is common, but that would not explain the belt melting smell.

So, keep an eye, ear, and nose to it!

 

[440Magnum]

Originally Posted By: scurvy
Originally Posted By: KeithG
I was able to get the compressor going by shorting the pressure switch. The gauges went to 0 and 90 PSI and its about 80F today.


If your low side gauge went to 0 psig & the high side gauge went to 90 psig, you may be undercharged or have a system blockage.


I'd say pretty clearly undercharged and likely leaking. A blockage would kick the high side way above 90 PSI on an 80-degree ambient day. That bugger is EMPTY. Odds are your noise after recharging is due to it having lost oil along with the refrigerant- any obviously oily spots on the AC plumbing? Oil schmear on the underside of the hood directly above the compressor pulley? If not, then (and I say this in hopes I'm wrong) the leak may be in the evaporator core under the dash. Unfortunately that's pretty common in cars since the early 90s and the switch to R-134a and aluminum evap cores instead of R-12 and copper/brass cores.