ok the title pretty much explains it i have an electrical mystery. when the lights are on the fuel guage drops and the blinkers will not work. when the headlights are off everything works fine. with the headlights on the emergency flashers still work. do i have a bad turn signal fuse or flasher that is drawing to much juice and staying on causing a drop in voltage which makes the fuel gauge drop?

so i just did a couple other things. i took out the blinker flasher and the blinkers still work with it out but real slow, and they are working with the headlights now. but the fuel gauge will drop with every pulsation of the blinkers does this make any sense?????? thanks guys

 

My Ford did that exact same thing... pulsed with the blinker. My "Brilliant" Electrical teachers didn't have much help for me

I'm guessin a weak ground?

 

ok update on this one with the brights not on the blinkers work. the drivers side will dim with the pulsation of the blinker not the passenger side. the passenger side light is brand new the drivers side is not. could the light be bad causing a bad ground? but it still doesnt explain why they dont work with the headlights on bright. unless the light is shorting out the whole system i think i will just buy a new headlight switch , blinker flasher and a headlight and go from there.

 

Maybe check the ground on the core support by the battery.

 

What he said.

 

Headlight Switch!! That is the first thing I would do after checking the grounds on the cab. I have had things kind of like this happen to our D-350 and W-250 a few times. It seems like when the headlight switch shorts out it makes everything else in the cab good haywire. Once my radio would shut off when I turned the headlights on turned out to be the switch that took alot of time to figure that out. After i took out all the quick disconnect plugs I don't have near the electrical glitches. The only bad thing about these first gens is the wiring!!

 

ok so i got the blinkers working bad ground! but now when the blinkers are on the fuel gauge will pulsate like down a little at a time. also with the lights on the gauge will drop at a steady rate. also there is no gauge lights now? tried anew headlight switch and nothing.

 

Is this on the '85 Chevy?

 

no a buddies 91 but..... i also had these same symptoms on a chevy once and never figured it out. sorry should have been a little more clear

 

So you fixed the ground on the core support and replaced the headlight switch?

It sounds like you have a cluster ground problem still. If you look in the sticky under "LED dash lights", Jim Lane wrote a nice how-to that includes cluster ground repair.

 

yeah i got a new headlight switch and that wasn't it so maybe i have a frayed wire somewhere or something is rubbing ill take a look in the sticky.

 

ok so the dimmer switch makes the fuel gauge drop so is it a bad headlight switch? but the guage lights also arent working so, im wondering if it is a bad ground of some sort

 

See my post #10.

 

yeah ill take a look at it closer thanks wanna