Fuse # 17 keeps blowing

[Otis Driftwood]

1981 F150 Custom Explorer

Just replaced the headlight switch, which corrected the problem I had with the headlights going on and off. Was hoping it would correct the dash lights too, but it did not. I'll replace the fuse, and all is fine till about a minute after I pull out of my parking spot, and then I'll hear the pop of the fuse blowing. 90% of the time it's fuse 17 for the instrument lights. Kinda at a loss. Anyone have any suggestions on where to start?

[Dyn Blin]

I was going to say to move to a relay set for the headlights to take the voltage off the switch (even changing the switch doesn't always relieve the resistance & heat from the  old wiring). But when you mention the instrument panel, makes me lean towards the Instrument Voltage Regulator.  Gary has a nice write up

[Gary Lewis]

Another idea is that you have an intermittent short on the illumination wiring.  Perhaps someone changed out the radio and you have an intermittent short on the light blue/red wire going to it.  http://www.garysgaragemahal.com/instrument-illumination1.html
 

[Dyn Blin]

Gary, would resistance in the wiring to the IVR input lead  ever see enough heat to trip the fuse?  

Or would the plastic film circuit ever get dirty enough to trip a fuse?

[Gary Lewis]

I doubt that would do it.

[Steve83]

Otis Driftwood wrote

...the fuse blowing. 90% of the time it's fuse 17 for the instrument lights.

Which fuse(s) is it the other 10%?

Dyn Blin wrote

...would resistance in the wiring to the IVR input lead  ever see enough heat to trip the fuse? Or would the plastic film circuit ever get dirty enough to trip a fuse?

Resistance REDUCES current through a circuit (and voltage to a component within that circuit); fuses blow because too MUCH current is flowing.

[Otis Driftwood]

The radio has been changed out, but has not worked since I bought the truck. Thinking about removing it entirely for now. Thanks for the tips, I'll let y'all know if that did  the trick.

[1986F150Six]

Often times, it is what has been added [by a previous owner] that causes electrical issues [i.e. radios and trailer wiring].

[Gary Lewis]

Amen, brother!  

[Otis Driftwood]

Removed the radio, taped off the exposed wires, and I am happy to report, that I now have consistent dash lights! Thanks so much for the help y'all!

[Gary Lewis]

Excellent!