I have to respectfully disagree with some members of alt.hvac who seem to imply that any A/C problem requires a "specialist", and that chumps like those who frequent rec.crafts.metalworking have no business even looking at A/C problems.
Just one case in point. A year ago my A/C sometimes would not start. (most of the time it would, but it kept getting worse)
A symptom was that in those cases, it would start if I gently kicked the outside unit.
After asking on newsgroups, and receiving responses from alt.hvac members about the need for "experts", and other responses from alt.home.repair boiling down to "open up the damn thing and use your multimeter", I opted for the latter.
Opened it up and quickly discovered that, drumroll, the quick disconnect that connected a 24V line to the contactor, simply broke from too much vibration and being made cheaply. It still kept contact most of the time, enough to operate the coil, and when it did not, the "kick" would bring it back into contact.
Another quick disconnect crimped on, and guess what, the A/C unit is operating quite trouble free since then.
If I simply called some "service company", I can imagine that the less scrupulous ones would try to sell me a lot of crap I did not need. The most optimistic scenario would be that after taking a day off work, and paying $75 for a service call, a tech would replace that same quick disconnect for free. Whether that optimistic scenario would be realized, is not clear.
So, while, no doubt, sometimes learned experts are necessary, they are not always necessary, and should not be called without some preliminary investigation.
i