outside mirrors not working in 1 direction
 

Both my outside mirrors do not work going to the right - i.e., to the outside for the passenger side mirror, and to the inside for the driver side mirror.

I removed the switch and took it apart and sprayed liberally with electrical contact cleaner. No change.

Got another switch at a junkyard. Took it apart and sprayed liberally with electrical contact cleaner, and replaced the original one with it. No change.

I don't think two switches in a row would have exactly the same problem with the right-hand direction, so the problem would be in the wiring or the mirrors themselves, right?

Was like this when I got it, so I don't know if both sides went out at the same time or not.

Any ideas what to start checking?

Anyone know how to check the switch and/or plug electrically, with a multimeter?

Any advice appreciated.

Since the same wiring is used when reversing current to the mirror motors and the other direction is functioning, it is very likely you have 2 defective switches.
Might be a good idea to get a new switch from Ford. Just plug it in and then see what you get.

I took both switches apart again, this time exposing the rubber membrane contacts and the corresponding contacts on the circuit boards. Cleaned by using a q-tip to rub a tiny bit of toothpaste (for a little abrasion) on the contacts before spraying with electrical cleaner again.

Both switches work now.

I like your procedure, especially since it works!! Nice job.