RV Repair: A/C Wont Start - Just Hums, mach iii, dyi

Question
Lately my Mach III just Hums when I turn it on. Last time I dropped the cover and spun the round cylinder while it was on and it started up. Today all the spinning in the world won't get it to budge. Can you figure this out before I have to buy a new unit? My unit is 2 1/2 years old with almost constant use. (Full timer) Thanks...

Answer
Hi Paul
First of all...has your 110vac connection changed recently?. Are you running more than 25ft of shore chord or has the condition of the adapter or molded end changed???    
You may  be drawing too much current, causing "capacitor hum".
You may need a "run" capacitor or a motor, but I can't be sure from here. "Prop starting" the motor will sometimes work with either problem.
Fan motors can be a DYI, but capacitors can BITE you, look for help from a household type A/C repairman, if not an RV tech.
If you have a voltage drop you will need to fix that before you throw parts at it.
RULE..."as voltage drops, current increases" , "current causes heat"

Thom
RV-PHD