If I turn off my AC while I'm out of the house for the day, or if there's been a cool day, when I turn it back on, the compressor doesn't start. It just hums and then shuts down, like it was locked up. It does this several times and then starts up OK. When the AC is on (at the thermostat) and the compressor and inside blower cycle, it starts right up. Only when it's been off for some time (10 hours?, a day or two), does it have the starting problem. I've had AC techs out numerous times. The first time this happened, all measurements were OK but he installed a 'hard start capacitor'. Didn't help. Everyone one who's been out since says the same thing - everything measures OK.

The only solution offered was to replace it. Since it uses the old refrigerant, I'd have to replace everything inside and out and the lines in between. (This is a standalone central AC unit; I've got hot water heat.) I've been hesitant to do so since it cools fine once it's running. The outside unit (Carrier) replaced the original 20 year old Trane and started doing this after it was about 2 years old (warranty expired, of course). And it's been doing this for the last 8 years. Any ideas or is replacement the only option?