1977 F-250 Instrument panel prob
 

Does anyone know why all my gauges (except the charging gauge) peak when I turn on the headlights> The needles on the fuel, water temp and oil PSI all move to the right and peak. When I turn off the headlights, the gauges move back to the normal position.

Sounds like you've got a short somewhere

I have been hunting but it is like looking for a needle in....
There are so many connections related to the dash and associated switches. Electronics is my weakness. Give nuts and bolts anytime.

Question... When did it start doing that? Were you fixing something, are you rewiring or replacing sections of the harness?

I'm in the process of restoring a '77 F250 myself... So, maybe we can figure it out... :)

Thanks everyone for you suggestions
 

To answer the question on what was I doing to at the time to make the gauges go funky. I hadn't been doing any work on it other than changing burnt out fuses. I just bought the truck last week and am still going over everything to make a fix-it list. I am going to pop the panel out to see if there is anything obvious. I will let ya'all know. :confused:

burn out fuses
 

When fueses blow there is something causing that to happen. go back and take a look at the systems that the fuses are protecting and see if there is any short in any of those circuits. Wire chasing and testing can be frustrating because of the way the harness is designed and connected to the engine and routed in and out of the fire wall. Try to get a wiring schematic of you truck and work from that. If no wiring schematic then try to visually check the harness and leads as close as possible. GOOD LUCK!

Thanks
 

I'll keep hunting through the spaghetti.

Narrowing the Hunt
 

Ok... now that we know that this was a pre-existing condition, let's see if we can reduce the spaghetti quest to some extent.

Fuse #2 takes care of I/P illumination and of course is tied into the headlamp switch... If fuse #2 was burnt then the first place I would start is the back of the cluster itself... The connector that connects to the back of the cluster feeds a circuit sheet that drives bulbs, guages, speedo, etc...

Look at the connection point and then the circuit sheet... if that doesn't have any issues, then start from the cluster connection and make your way back to the headlamp swtich...

Maybe you've done this already, but just a thought as to a place to start if you haven't...

As geomath suggested, a wiring schematic is the best thing to have for these issues... Chilton's has books for the '77 with nicely detailed schematics at the back...

Good Luck...