Master switch issue

[Smroot]

Hi all,  I have an issue with the master in my Encore.  When I turn the master rocker off the power stays on.  If I recycle I can get it to shut off.  Doesn’t happen every time.  Cleaned with contact cleaner but still happens.  Before I spend $435 on a new switch I’d like to hear any thoughts that it could be a different problem.  

[EricJ]

Master relay may be sticking.   It's near the battery, the master switch turns it on and off.

[Aerodon]

There are several connectors in the circuit from the avionics relay to the ground.  If any one of them were open or intermittent then the switch would not ground and the avionics would stay on.

Some switches have 2 poles, only one in use.  Swap the ires over to the other side?

But if there is a fault in the small control relay, this could provide an alternate path to ground to hold the avionics relay in the on position. 

And the avionics relay could be sticking.

 

Aerodon

 

 

 

 

 

[rgpilot]

If it happens to be the relay, new relays are available from Peerless Electronics on L.I.

Available and much less expensive than from Mooney. 2 years ago about $450

They are made in Germany and are exact replacements.

[Smroot]

Erik J,

Could I clean the master relay with contact cleaner?  What does it look like?  I have a hunch that’s the problem.  Not the switch.  
Tim

[EricJ]

31 minutes ago, Smroot said:

Erik J,

Could I clean the master relay with contact cleaner?  What does it look like?  I have a hunch that’s the problem.  Not the switch.  
Tim

They're usually sealed up reasonably well, so it might be tough to do.   They're usually reasonably easy to replace.   I think on your airplane it's next to the battery box in the tail.

[N201MKTurbo]

You might try to disassemble it, if you can, don’t bother with contact cleaner, you want to sand or file the pits off then polish to about a 1000 grit finish.

Those contactors usually have a spring loaded copper disc connected to the solenoid armature that contacts two massive copper posts.