We have a fairly old central A/C system that has required very little repair
over its 25-year life. It is a dual-zone system. Recently, one compressor
started running only intermittently. Today it would not start at all (just
the inside fan came on, but no compressor running, no cooling).

In trying to trouble-shoot this problem myself (at least to see if I could
find the root cause), I confirmed that the normal voltage existed across the
wires from the thermostat, but discovered that at least one of the two
"pressure switches" has an open circuit -- these "pressure switches" are
wired in series, between one of the thermostat wires and the compressor
control unit. I think that each of these "pressure switches" monitors the
refrigerant pressure (one pressure switch on each of the refrigerant lines
leading back to the house), and is supposed to interrupt the thermostat
voltage if the refrigerant pressure gets too high.

I seem to remember, for example, that if you run the A/C, then turn it off
(by raising the thermostat setting), then immediately turn the A/C back on
(by lowering the setting), there is a chance of "blowing out the
compressor," since when it comes back on, the pressure it's pumping against
is still very high. So, probably a main reason for the "pressure switches"
is to prevent the compressor from starting up if the refrigerant pressure is
still too high from recent pumping.

Anyway, to see if the problem really was just one of these "pressure
switches," I shorted the two of them out. The compressor started like a
charm, and has been running perfectly, cooling the house.

My question: If I continue to run the A/C system this way, with the pressure
switched shorted out, until I can get them replaced, am I running a major
risk? Should everything be OK as long as I'm careful not to re-start up the
A/C right after it has been turned off? I.e., if I'm careful to wait 5-10
min before re-starting the A/C (or just let it cycle normally via a fixed
thermostat setting) is there no danger of "blowing out the compressor?"

Thanks.