320I Wiper Switch don't turn off

Hello there:

I have a little problem with the wiper switch of my BMW 320I 1978 USA Version.

This is the problem: I can't turn off the wiper, I can change the speed, but I can't turn it off, my guest is that the Wiper Switch is the problem, and for a "quick" solution I soldered it and I can turn it off, buy I have only one speed, hehehehe.

I have tow questions:

1.- what other thing can I check out besides the wiper switch?

2.- can I fit a wiper switch from a BMW 320I 1977 on mi BMW 320I 1978?

thanks for your help.