Groaning Noise From The Evaporator

[Doug]

Hello, new here. I'm having a problem, sort of, with the a/c on a '83 El Camino. I bought this car a year ago and immediately replaced the compressor, the accumulator, o-rings and orefice tube.

I had it professionally flushed, vacuumed, oiled and charged and it's been working great for the last year (and still is.)

The problem is, when I first fire off the a/c I get a groaning noise coming from the evaporator area that goes away after 15-30 seconds of operation. I get the same noise (sometimes, but shorter in duration) on shutdown. The noise sounds like a sick dog in heat. It's like something has to equalize after it's running to make the noise go away.

The replacement compressor is a new (not rebuilt) Four Seasons and I can neither feel or hear a vibration coming from it that could transmit itself through the lines. Also, the R-134 sticker under the hood says they put 41 ounces in it.

Thanks for any and all help in solving this issue.

[tbirdtbird]

Has the noise been there from the start?
Does it vary depending on fan speed?
Vary with temp setting?

[Doug]

The noise started when I had it charged. I ruled out the blower motor because it also does it when the blower motor is disconnected. Changing the temperature slider doesn't change anything, noise-wise. There is no noise when I change it to heat.

Thanks -

[Tim]

Were you using the same compressor from a year ago and had to have the system recharged recently?

[Doug]

The system is virtually untouched from when I repaired it a year ago, hasn't been recharged. Thanks -

[tbirdtbird]

Glad it is not a reman comp. However, we generally have seen 4-squeezins quality to not be up to par, even if new.
I am still suspecting the comp.
Time for some pressure readings.
Pressures (hi and lo, thus using a professional manifold gauge set) should be taken with RPM at 1500 , max fan max cool, recirc, doors open (a true load test), and ambient stated, and center vent temp reported.
Report back

[Doug]

Sorry for the late reply. I will perform this test in the next couple of days and report back. Thanks again.

[Doug]

I'm back. The ambient temperature was 80 degrees with low humidity. I had 40-41 degrees out of the center vent with recirc on, full blast. With the low side valve closed at the manifold my readings were 35 low, 275 high. Thanks -

[tbirdtbird]

Your symptoms are a bit baffling.
Since they began immediately upon the recharge, at this point, along with the hi side being a bit hi at 275, you may be overcharged. I would suggest you have the system reclaimed, evacuated, and recharged to spec. The sticker says 41oz but how much did they actually put in? And how much oil?
I would have brought it back to them when the shop first charged it

[tony1963]

I've had the same issues on the GM orifice tube systems of that era. You may be slightly overcharged and the orifice tube is the source of the groaning noise.