Repairing home air conditioners (Failing compressor)

This is a followup to the earlier post about repairing air conditions. This post however is more targeted to an experienced DIY person because we will discuss electronics.

Symptoms:
1. Compressor fan starts but dies a couple of seconds later.
2. Compressor fan starts only if you manually help it turn.
3. Compressor outlet pipes not cold.

Please note that there are some air condition units which switch off when the compressor fails as a safety mechanism. So if your air condition unit switches off after a couple of minutes, then check the compressor.

These are the symptoms of a bad 'run capacitor' - a run capacitor helps a single phase motor to start and keep it running but holding electric charge. The run capacitor in an air condition unit is called a Dual Run Capacitor because it supports two electric motors - the fan and the compressor. If the capacitor busts or weakens by time (loses more than 10% of the holding capacity) then you need to change it.

The capacitor looks like this:

The only tricky part when replacing the capacitor is to pay attention to the terminals:

C: common
FAN: fan
HERM: compressor

Also make sure you use the same voltage rating -  440 volt capacitor can be used in place of a 370 volt, but not a 370 in place of a 440 volt. The microfarads must stay the same within 5% of its original value.

Good luck!