What should I do about an outside a/c unit that hums but won't come on?

Answer by  mlucas (515)

The old hums but won't come on problem. The problem could be as simple as a capacitor, low pressure or a bad contactor. Call a Professional.

Answer by  strohs21 (181)

Humming noises generally dictate electical problems, this sounds like it could either be the condensor fan motor or a bad contactor. Contactors are generally inexpensive and the best place to start. I would recommend replacing that first. Make sure all power is off when installing new contactor to avoid causing shorts.

Answer by  Brandon (16)

Look for ice on the lines leading into the house. This could indicate a freon leak. Check to see if the fan on the outside unit is actually turning. If it is not moving you can attempt to turn the fan with a long stick, but be very careful.

Answer by  Azrael (27)

First and foremost, if you are worried about it, disconnect it from main power! If this can't be done safely, get someone around who is qualified and able to disconnect it. Then you should find someone to inspect the unit ASAP

Answer by  Liz59 (10966)

Basically, the parts in your unit have been overworked. The humming sound indicates that the parts are burned out. Thus, you need to be able to repair and or replace the parts.

Answer by  LeheckaG (1826)

Outside "A/C" unit "humming" means that your compressor motor or cooling fan motor has a bad starter capacitor or starter winding(s); contact your HVAC service contractor.

Answer by  champaign9497 (11977)

Change the contacter first and see if that fixes it, it could also be the capaciters or a relay switch as well the easiest way to fix the problem and probably the cheapest would be to call your local technician he will be able to diagnose and fix the problem much quicker than you could on your own.

Answer by  Nic (99)

Call an a/c repair man!! Turn off the A/C unit, at the breaker if necessary. The motor is probably frozen on the outside unit. Don't run it until fixed, due to potential fire hazard!

Answer by  Liz59 (10966)

Well if it is hum and it won't come on, then that indicates that there is some major damage to the machine. You need to contact the customer service for more support.