installed a NO SCHOOL side mount plate with MODEL A tail light, Figured out the wires and made a ground for the tail light. All hooked up, running light works fine but I get no effects from the brakes (the red / yellow wire). I have no turn signals (removed). I soldered the new wiring into the old harness. Any help would be great.

 

In order to help you solve your problem I would like to know how many bulbs this model a light has and if there are single or dual filament lamps.

Could you post some images?

In general I can say:

Types of bulbs used in taillights are:

- Dual filament for brake/tail light 20W/5W



- Single filament 20W as brake light



- Single filament 5W as tail light

- Festoon bulb 3-5W as a tag light.



Color codes to use on a Dyna 2004:

Blue for running/tail light and tag light

Red/yellow as brake light

Black to ground

Here's in image I posted some time ago on how to wire a double filament taillight:

 

one double filament bulb. The light itself had 2 wires (green / black) coming from the light housing, I made a ground and attached it to on of the mounting bolts and tied it into the stock ground coming off the rear connection. Do the signal wires or the acc. pwr wire need to be tied in somewhere to close the circuit??? I am confused on why the brakes dont trigger the brake light but the running light works fine. I wired mine the same as your diagram. Thanks bro

 

If the running light works fine, the circuit is closed imo.

Some points to check out:

- check with a probe light or a multi meter if you have any power coming from the brake light signal wire
- check if the brake signal wire is connected properly to the lamp fitting
- does the double poles make good contact in the lamp fitting
- is the bulb OK?
- are the fuses OK?