Air compressor on Heil air conditioner is humming but not kicking in

SOURCE: heat controller mini-split air conditioner

Check each screw on your compressor to ground (compressor case). Should be very high resistance Then check the resistance across your teminals on the compressor to be sure it is not shorted. Then check the wiring to your capacitor (The big one). I ran across this just last week. The mechanic didnt have the capicator wired correctly. If it is brand new it will have a wiring schematic somewhere on it.
Dont leave the compressor on very long, but turn it on long enough to get a voltage reading across the terminals. I assume it should be 240 volts. If you have check all of this, they make a jump start gadget to start a stuck compressor. They sell it just about everywhere. Let me know how this comes out..

SOURCE: My new Amana compressor Central Air-Heat Pump hums very loudly

When it hums, is it running? Or does it not run when it hums? I'm assuming it runs when you say you have to turn the therm off to get the noise off.. If it's humming and not running, you have big problemo friend..

SOURCE: Window Air conditioner pulls too many amps

Probably Seems Replace Running Capacitor Located in Component Box or Nearby Compressor

SOURCE: CARRIER MODEL 38YCA030370 MAKES HIGH PITCH ELECTRICAL HUMMING NOI

Yes it could be the pop off pressure relief on the compressor.
I assume it is the outdoor fan your referring to not running.

If this is a heat pump and it is in defrost (only in the heating mode should your outdoor fan be off and then for only a max of 12 to 15 minutes).
If it is just AC ir is Heat pump in cool mode, the out door fan should run while the compressor and indoor fan are on. Until the thermostat is satisfied on room temp.

This high pitched squealing is indicative of a bad fan motor or capacitor for the out door fan motor. Kill power and test blades to see if turns free. Check the run capacitor inside control panel. It is usually silver or aluminum colored (some are painted gray). The top should be flat with rolled edges and the sides should either be round or oval shaped with no swelling or oil leaking from inside it. If this all looks normal take it to where your going to get a motor any way and ask them to check it or sell you a replacement at the same time. These can go out usually from high voltage (lighting...) or from over heating (bad fan motor, dirty out door coil...).

Hope this helps you if not post back I'll respond as soon as I can. And please rate me as high as you can. Thank you for using Fix ya and good luck.

SOURCE: air conditioner hums then shuts off

Replace the start/run capacitor.