another dash wiring question

[76bonanza]

I am trying to wire in the brake warning light to an led. But the brake warning light on the harness never gets power. I thought it came on when you started the truck but it never gets more than .5 volts not enuf to turn on light. How do I know if it will light when brakes freak out?

[71tahoe]

The wire that goes to the valve that connects to the master cylinder. It should have a wire connected. When you touch the connector to ground it should light the dash.

[76bonanza]

I see so pull wire on MC ground it and it should lite the dash? So the switch in the prop valve grounds when it is tripped makes perfect sense.

[71tahoe]

Yep. That's the only way a single wire could complete a connection, to ground. I wouldn't guarantee that's the only thing needed to light the bulb though.

[Longhorn Man]

well, actually, it IS supposed to light up when you have the key in crank position.

[76bonanza]

upon futher testing the tan wire from harness has to be hooked neg on l.e.d and positive on l.e.d to 12 volt, then when I ground wire at MC it lights but still does not light when key is turned or do you actually have to crank motor over for it to light?

Thanks for help.