Main dipped headlights not working

67Dart273, you said:
"With the light switch in "head" "any two" of the dimmer switch terminals should be hot. If there is only one, you have bad dimmer. If you have two terminals hot,"
IF you have headlights ON, wouldn't only one terminal be "hot" at a time, (either HIGH or LOW)? Now as I type this, I think I see what you're saying; you will have 2 terminals hot, because if you measure to ground, you will get voltage on the common terminal (feed in from switch) and one or the other of the remaining terminals (HIGH or LOW out) correct?
If that's the case, it wouldn't be "any two" because if you tried HIGH to ground, then LOW to ground, only one of those should be "hot" at a time, no?
Unless I'm confused, in which case anything you can do to help clarify would be appreciated, because I will be needing to wire my project up and I'm hoping to not have a bunch of issues.

I'm talking about the switch "as a whole." You don't even need a diagram to TS a dimmer. There is power into one terminal of the dimmer with the HL switch on so that is one terminal hot

The switch is SPDT, so there is always one output. You don't need to know which one, because if you switch it, the dead terminal should become hot.

Therefore any two terminals should be hot when the HL switch is on.