I have a '84 Pick up that i switched dashes on. I ended up switching the whole dash, that included the left side, from a 4runner. It has this extra button. What's it for? Was it for the rear window defrost? I'm thinking of using it as an on/off switch for trail lights or a rear bed light or something like that, but first I'd like to know the original purpose.

 

That's the Clutch Start Cancel button. Normally the starter won't operate unless the clutch pedal is pushed down and hitting a switch. This lets you use the starter with the clutch out.

 

I have that same button on my 87 pick up. I use it all the time. It lets you start it without pushing in the clutch if you hit the button first. It was nice when my clutch finally was on its way out I could start it using the button then drove it to the shop

 

I've heard of that button, but my '85 doesn't have it... It will also start without the clutch pushed in.

 

That's the factory installed NOS button or at least that's what you tell jeepers