[Afirehawk1]

Originally Posted by ACK

Most multimeters have a continuity function, it's the symbol below. Unlikely, but possible, the switch has the brights on in both positions and it's just turning the low beams on and off (in effect, you have brights and even brighter brights). If one of the poles has continuity when in both positions, you have your culprit.

For the tail lamps, if you haven't, I suggest disconnecting the harness under the rear bumper and take voltage readings from each of the wires as follows:
1. all lights off
2. all lights off and brakes on
3. running lights on and brakes off
4. running lights on and brakes on
5. running lights and head lights on and brakes off
6. running lights and head lights on and brakes on
If they all check out okay and you have decent voltage readings, you know the harness coming out of the cab is good, so the issue is definitely at the back half of the harness, which makes it much easier. If that's the case, most likely it's one of the following: the wiring and connections to the tail lights need to be reconfirmed; need better grounds to the tail lights; the LEDs don't want to work with 50+ year old technology.

As a side, I'm in the camp of not using LEDs on the truck, with a few exceptions. LEDs have requirements that don't mix with older vehicles, so they have a habit of doing some very odd things.

Update on the Hi Beam Bright light staying on—-
The green and ground were flipped backwards which caused current bleed over.
Lesson on this one
Pix to illustrate