I want to wire up a third brake light on my contractor cap for my 1997 2500.
The internet says there should be a factory wire provided for this sticking out of the harness near the spare tire.
I have dropped the spare tire but don't see anything.
Can anyone confirm that it exists on 1997 models? I have a third brake light on the cab.

 

I haven't even glanced at it in so long, but I recall a 7-pin trailer connector in the bed of my '96. I assume that is OE. Does your '97 have that? I don't know if that connector is connected from the factory, though. Check your PMs

 

I have a 7 pin, not OEM, but that doesn't matter....you cant take brake lights directly from the 7 pin because it is shared with the turn signals and it would flash when you use turn signals. If I could do that I would just take it from the brake lights.
There is an extra wire on some trucks, specifically for a third high mount brake light, called CHMSL (center high mount stop lamp). Some trucks have it, apparently mine doesn't.
But I sorted it out and ran a wire directly from the brake switch at the pedal. Its the white/tan wire if anyone cares.

 

Good point - I didn't think that through far enough

 

Here is what I gleaned from the service manual wiring section. You can tap into the WT/TN brake wire at C203 located near the drivers side firewall.

 

I understand what you're saying, but I actually have a different perspective on this issue. It does matter whether your 7-pin connection is OEM or not because it can affect the wiring configuration and what functions are available. I mean yeah, while it's true that the brake lights are typically shared with the turn signals on a 7-pin connector, there are ways to separate them to prevent the flashing issue. One common method is using a relay or diode setup to isolate the brake light circuit from the turn signal circuit. For example, this allows me to tap into the brake lights without interference from the turn signals)

 

My FSM says white wire with tan tracer for 2001....

Kurt

 

Ok, but what I was asking about was the factory wire that eliminates the need for any diodes/relays/logic controller.
Some trucks have an extra wire in the harness labeled "CHMSL". The wire is not connected to anything at the rear, and it comes out of the harness near the spare tire. That wire is specifically for a Center High Mount Stop Lamp that is found on caps and campers.
Now it may be possible that the extra wire only exists on trucks with factory 7 pin trailer connectors....that's what I was trying to figure out. Because my truck doesn't have the extra wire and some do.