Input override question

I am new here and have been working on an LED array. Currently I have a work test circuit with 27 piranha 5mm LEDs. Circuit has two inputs both are 12v DC input A lights array at 50% intensity, input B lights array at 100% intensity. Input B overrides input A and works fine. I want to add a third input "C" that will override both A and B but can't figure it out.
Here is an example of what I have.
View attachment 68957

My goal is to have input C use a chasing circuit and override the B input. At this point I feel I may need to look at using a chip to control?

I'm not sure what your goal is here... you won't get any brighter than input B. if you want to 'disable' A and B, then use relay contacts to open them up, either prior to or after the diodes. Oops, one set of contacts at the common point after the 220 ohm resistor will open both inputs up. If you want a low, medium, high, change input A to a slightly higher value, set input B to, say 200 ohm (150-180?), and input C to direct connect.

It depends on what your purpose for the C override is... to make brighter or turn off...

Look at it this way. I have two LEDs and two switches, the 12VDC source for switch A is constant and the 12 VDC source for switch B is pulsed. When switch a is closed and b open both LEDs are lit and steady. When switch a is open and switch b is open LED 1 is constant and led 2 is pulsed.

I don't know if I should look at building a logic gate or if there is a chip I can use ?

How about this? The dual pole, dual throw relays disconnect inputs A and B and isolate the 6 columns for chaser pattern inputs. A 6 pole, dual throw relay would be better.

In case you don't REALLY want to disable the brake lights and turn signals, try this one.

Thanks I will give it a try