A/C Chatters/Gobbles at idle

[slownis]

My A/C on my '92 Ford Ranger has a chattering sound at idle. My wife says its like a turkey gobbling. I'm perplexed by this, so I'm going to write down everything I have done.

First thing you need to know is that this is not a new problem. Last Summer (summer of '10), I decided to finally fix the A/C on the truck. I got a rebuilt compressor from napa, and a new drier. We did this at my neighbor's house so we could use his air tank to properly flush the system. I didn't change the condensor at that time. We got it cooling, but it had this chattering sound. I marked it up to the fact that the neighbor used PAG oil, but this was a retrofit, so we should have used esther. Driving down the road the sound went away.

Fast forward to this summer. Somewhere between then and now, the refrigerant had all leaked out again. I decided to just replace everything, and I mean everything. I removed and replaced the evaporator, the condensor, the compressor (which was still under napa's warranty), and o-rings, the orifice tube, and the accumulator. The only original pieces are the two lines, which were flushed. This time I filled it with esther oil (8 oz, 100 weight), putting half in the new/rebuilt compressor and half in brand new evaporator.
We refilled it with refrigerant using my neighbors guages. It cools, but the chattering sound was back! Again, only at idle....

What did I do wrong this time?

My neighbor noticed that the high side seemed to read a little high at idle, so he suggested I add an axiliary fan to cool the condensor. I did that, but it didn't fix it. Still chatters like before.

I haven't tried changing the belt, or the tensioner. The Main cooling fan for the truck seems a little warn, but the fan clutch seems stiff. Part of the fan shroud is missing.

 

[4x4junkie]

I would think a chattering sound means a faulty compressor (I've never heard one good word about rebuilt compressors, especially regarding the Ford FS-series compressors). It's difficult for anyone to make a diagnosis just by the description of a noise though.
How much R-134a freon did you put in? (and what engine is your truck?)

FWIW, PAG-46 oil is the preferred oil with a new/rebuilt compressor as long as all the old R-12 mineral oil has been removed (which is what I used when I did a retrofit on my 1990 2.9L a bit over 3 years ago).

 

[ksum25]

Sounds like the same problem I had with my BII. The problem was too much pressure in the system. The pump would make a weird sound the the hoses were vibrating. What happened in my case was I added the refrigerant when the system was cold, but after a few miles of driving the pressure would be almost 30 -40 lbs too high. all I did to fix the problem was to drive the truck for 15 min then set the pressure and never had a problem again.