I used a similar method to the one suggested by Bordew.

I used to do a lot of service calls to mobile homes wired with aluminum. Usual complaint was that 1/2 the stuff didn't work. I'd turn on every light switch & table lamp & then beat on the walls with my fist (rude & crude, I know) & when the lights flickered, went to the nearest box & tightened the connection.

This method really does work, but the customer really expects to see something more high tech than a fist or rubber mallet.

Tom

Few things are harder to put up with than the annoyance of a good example.