Author Topic: Correct Alma compressor for 6.9?  (Read 348 times)

p. rex

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  • Crazed 6.9 owner
  • Location: Austin, TX
Re: Correct Alma compressor for 6.9?
« Reply #15 on: 02 October 2019, 08:57 AM »
Hooray, more problems!  I picked the car up yesterday.  The good news is, the AC is cooling very well and the ACC flaps and servo seem to function correctly.  The bad news is that I am getting an ugly whirring noise from under the hood when at speed, like a bad bearing somewhere.  It's not audible at idle.  I can't hear it when the compressor switch on the dashboard is turned off, so I assume it's my old compressor.

From what I've read, the fact that it's noisy when engaged and quiet when turned off indicates that it's something in the compressor itself.  I think that my mechanic put in a little more R12 than is indicated, maybe four ounces, but he says the pressures are good, so I don't think the refrigerant charge is off by enough to cause this problem.  Maybe it's a bad shaft bearing or other mechanical problem inside the compressor?

What are the odds that this thing lunches itself and destroys a bunch of other A/C components?  Should I leave the A/C off until I can get the compressor replaced?  I am having my guy look at the car later this week, but I suspect I've already got my answer.

Thanks!
1979 450SEL 6.9 #7184 “Die Marschallin”

p. rex

  • Enthusiast
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  • Posts: 25
  • Crazed 6.9 owner
  • Location: Austin, TX
Re: Correct Alma compressor for 6.9?
« Reply #16 on: 02 October 2019, 07:40 PM »
I have done some more driving and listening.  The noise is intermittent, not continuous.  It seems worse between, say, 1500 and 2500 rpm.  It is difficult to describe — something between a crackling and a whirring.  Not seriously offensive or loud, you have to be listening for it to notice it.  Possibly the shaft seal?  Is it possible it could only leak while running?

AC performance is surprisingly good.  The flow from the blower is not overwhelming, but temperature ranges from pleasantly chilly to balls-cold, depending on whether you’re moving or not.  I was putting around in the late evening in 90-95 degree temps and it was having no difficulty at all keeping things cool and comfortable.
1979 450SEL 6.9 #7184 “Die Marschallin”