single phase ac motor runs forwards or backwards

[kickstartthedog]

hi all hope you can help. i have a single phase ac motor which turns freely by hand but wont start under its own power it just hums until it trips out overload. to make things interesting though if you apply power to the motor and then turn it by hand it will pick up to near full speed. whichever way you turn it so you can end up with it running at neally full speed in reverse switch it off and wait for it to stop re apply power turn the shaft by hand and have it spin near full speed in the opposite direction.
thanx in advance for your answers as i have just torn out the last of my hair

Dave

 

[Modernelectric]

Is it a capacitor start motor?

 

[kickstartthedog]

dont know i havnt removed it yet. job for ron

 

[ajelec10]

It shouldn't matter what type of single phase motor it is, it could be induction start, capiactor start etc could have a centrfugal switch in inside, what i can tell you is that the a single phase motor ahs a start winding and a run winding, the start winding is not working and thats why it sits and hums as it cant decide what direction it wants to run in, this could be a faulty winding, centrfugal switch, or capiactor, or could be a fauly control swicth if you can make the motor spin forwards and backwards via a control swicth when it was working that could also be at fault.
Hope this helps

AJ

 

[MikeCDF]

Have you checked wiring correct - also internal connections - as per JB cover.
If wiring OK then most likely capacitor - has motor being sitting around not working for a long time!
If wiring OK and capacitor OK or changed then replace motor is my advise. You can spend more time troubleshooting than getting the installation working.

 

[peteludman]

i had this and it was the capacitor