Why does my car's ac keep blowing up?

Sorry for this not being properly crossposted, I meant to but forgot to add this news group to it when I put it on rec.autos.tech A lot of folks here in home repair know AC systems so I thought there might be some good ideas here. -----------------------------------------
Twice now my 92 Explorer has "blown" the compressor. In both cases it blew very shortly, within minutes, of starting the truck. It blew so shortly after starting the truck I have a hard time seeing how the pressure could be high enough to "blow" but in both cases it popped the high pressure relief valve and spewed oil and refrigerant out. The first time it did it I had started the truck, pulled out onto the street and immediately hit a red light. While at the light I put it in neutral and gave it enough gas to rev up the engine to 1500 rpm to run the compressor enough to get more cooling in the 100 degree heat. After less then a minute of waiting at the light there was a grunge/screech/smoke/smell and no more cooling. Seemed like the compressor had locked, oil blew, fan belt screeched over the locked pulley and the oil burned on the exhaust manifold. Then it unlocked but no more cooling. Upon tearing it down there was the expected "black death" look to the oil, it had about 100K miles on the system, and metal bits at the orifice tube screen. When I took the compressor apart there were broken bits and obvious new wear marks on the internals. I got a new compressor, accumulator, orifice tube and condenser and flushed the evap and all lines. Put it back together and it ran fine for 4 years.
Then last month I started it up after it sat all day, about a 95 degree day. Started it and just let it idle for no more then 1 to 2 minutes while I arranged my stuff before leaving. Then grunge/screech/smoke/smell and no more cooling - same thing again but I hadn't even sped up the engine. Immediately turned it off. Got out and looked, oil blown out all over the engine again. Turned it back on and the compressor spun freely, no funny noises, but no cooling. Unlike the first time, when I tore it down I didn't find anything much in the system, no little metal chunks, just a little bit of "blackness" to the oil, a small amount of sludge on the O-tube screen. The inside of the compressor did not seem to have any broken parts. From how everything looked I might have been able to fix it by simply recharging it but I had already ripped the compressor apart. So I bought all new parts again and redid it last week. Got a compressor, accumulator, o-tube and condenser from rockauto for $220. Now it's cooling fine.
Then about 3 days after fixing it I was at the SAME park where it had blown the second time. Started it up and heard what I thought sounded like the grudge noise - like the fan belt was just starting to slip and was fighting it. After having heard this twice before I immediately turned it off. Thought maybe, just maybe I smelled a tiny bit of burning oil but there was no smoke like the first two times. Drove about 3 miles to the store with the AC off and a frown on my face. Popped the hood and disconnected the compressor. Then started the engine and turned the ac on. Then plugged the compressor back in while I watched under the hood. Compressor came on, no funny noises, and it started to cool!! In fact, it seemed to be working perfectly normally. So I presume I caught it JUST in time before it blew out the high pressure blow-off again and spewed oil everywhere.
So at this point my thinking was that maybe I was putting too much oil in the system and slugging the compressor on start up. So I pulled the one week old compressor back off and checked the oil level. It was actually on the low side, certainly not at all overfilled. So put it back together and it's working just fine.
Sorry for the long post, ...
why is this system blowing up within 1 or 2 minutes after a "cold" start???? It's always in the 1 or 2 minutes when I would think the system isn't even working hard yet.
Every time I start the engine (and AC) now I have my finger ready on the AC on-off button ready to shut it off if I hear the slightest funny noise.
I put in 80% of the amount of R12 as I'm using 134a. Running it in the driveway at 2000 rpm I've seen the low side drop to 30 and the high side go to over 325. I don't see how they could possibly go even that high, much less to the 400 psi needed to pop the high pressure valve within 2 minutes after starting with the engine at or near idle speed.
Anyone got any theories? Too much oil? Too much refrigerant? Not enough virgins being sacrificed?
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wrote:
Not familiar with Ford compressors, but I've had enough trouble with rebuilt GM's that I won't buy them anymore. New only. You buying rebuilt?
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On Fri, 16 Oct 2015 00:45:36 -0500, Vic Smith

Nope, always new for this vehicle. On another vehicle (GM A6) I went with rebuilt because new was so expensive... and the first one lasted 6 months, the second one was defective out of the box, and the third only made about 1000 miles before the front seal started slinging oil. Ultimately buying new would have been cheaper but it's hard to lay out the money all at once when you can bleed to death slowly......
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