Parking Brake Woes...

[soule64]

Hi. I sure hope somebody here can help. I normally hang out in the 67-72 section, but my son has a 76 C-10 that has a problem that I can't seem to figure out. (I did search the site before posting without much luck). Just out of the blue, the parking brake light on the dash came on and stays on when the parking brake is engaged or released. This light has never come on - with the brake on or off - in the three years that we owned the truck (I thought it was dead). I think 'Ok, no problem - there must be a switch that contacts the brake lever and it is now live'. I checked the schematic in the Haynes manual and it shows that the only circuit for the light goes thru the 'brake indicator switch'. But as hard as I looked - I could find no switch or wires anywhere near the parking brake. So then I am thinking 'well, maybe it is wired to indicate a fault in the system' and sure enough, one of the brake lights is burned out. After a few high-fives thinking that we solved the mystery, we replace the bulb... and the indicator light in the dash stays on. I did read a post on the site that said that the brake proportioning valve might be causing the light to illuminate, but I don't see how the light is wired thru it. So, my questions are:

1. Is there a contact switch for the parking brake? If so where would I find it? There is nothing in the manuals that I have. (a pic would be great because I have looked over the entire assembly!)

2. Is the "BRAKE" indicator light on the dash just for the parking brake ('on' when engaged, 'off' when released) or is it used for some other fault condition?

3. Is the brake proportioning valve somehow connected with the indicator light staying on? The brake lights (exterior lights) now work fine after I replaced the R/H bulb.

I apologize for the length of this post and the fact that I have probably over-analyzed the problem, but I feel like an idiot for not being able to fix it. Any help or suggestions that anyone might be able to provide me and my son are greatly appreciated. Thanks.