Actually I don't trust contractors [change
intentional] at all. Too many
"electricians" have swapped hot/neutral and messed up the grounds. Always
verify EVERYthing.
Tell me about it!. I've seen single-pole switches in the neutral wire,
live/neutral swaps, neutral/earth swaps (get a couple of extension leads
with those 2 faults joined together and you can get the lethal live/earth
swap!), under-rated cables, etc, etc, etc. The only person I trust with
the mains is myself (and even then I am not sure I trust them!)
I will admit that I have never tried to repair a contractor, it might be
possible, although I think some of them should just be screpped.
Contactors, on the other hand, are easy to repair. Often repair kits (new
contacts, new coil, etc) are available.
-tony