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Dashlights dont work when the headlights are on.

Dominic Torreto

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I have a 1970 charger and for some reason the dash lights dont work when the headlights are on. The turnsignals also flash really slow when the headlights are on(and no it is not the battery I put a new battery in and it still does the same thing even on a battery charger). When I pull the 20 amp running tail light fuse out the turn signals flash like they should and the dashlights do work with the headlights on. Dont know what is causing this.
 
Sounds like you have a ground problem somewhere.....
 
Do you have a good ground on the gauge cluster? Have you changed anything lately ? New car to you? Need more info.
 
No have had this since 2012. Nothing different has happened other than cutting all lights to the tail lights
 
cutting all lights to tail lights?
 
The tail light fuse has to be used for dash lights. If that fuse is removed you will not have dash lights. System works this way. 1-The 20 amp fuse feeds a set of contacts in the headlamp switch. 2-When the headlamps are turned on that circuit feeds the dash light dimming control. 3-The dimming control then powers back to the lower amperage instrument fuse. 4-From the instrument light fuse it goes to the orange wires which feed all the instrument lights.
 
We figured that part out. Is it possible that the headlight switch or the dimmer dashboard switch could be bad and cause this?
 
try to ground one of the tail light sockets
 
I have a 1970 charger and for some reason the dash lights dont work when the headlights are on. The turnsignals also flash really slow when the headlights are on(and no it is not the battery I put a new battery in and it still does the same thing even on a battery charger). When I pull the 20 amp running tail light fuse out the turn signals flash like they should and the dashlights do work with the headlights on. Dont know what is causing this.
Did you turn the dash light switch up?
 
Did you turn the dash light switch up?
On my other post which is turn signals only. Someone stated I shouldnt have any voltage going to my turn signals even if the headlights and turn signals are off. In other words I do have voltage going to the turn signals when everything is off. Would that effect the dashlight scenerio as well?
 
Voltage appearing where it should never be is always a concern. Since you have not witnessed smoke and fire you should consider yourself fortunate. This may be a timely journey but it appears a wire is in the wrong place, a short between two wires exists, or a few other possibilities.

Many moons ago when I was an active duty Air Force technician working aircraft systems with literally miles of wire, a troubleshooting technique called "Divide and Conqure" was our best friend. Basically, one isolates the issue by breaking connections along the way. If problem goes away and returns as the connection is opened and closed, you have isolated the fault area.

I have used this same logic many times while working of vehicles.

Good luck. Don't give up!!
 
Fixed both probpems with the dash. Everything is working now. The black wire to the dash motherboard had power in it for some reason when I cut that and grounded the motherboard everything including the turn signals and dashlights started working
 
Update i guess you need that black wire for the 12 volt but I ended up finding out that dashlights still work. The problem actually was the dash needed to be grounded the whole time
 
This is the diagram for anyone in the future that is having issues with gauges or dashlights. Make sure your dash casing is grounded. Use a testlight and make sure its not getting power. Also in this diagram that pin thqt looks pink is NOT A PINK WIRE IT IS PURPLE!! If this helps anyone give me a like so I can be even more popular.

Screenshot_20230205-153048_Messages.jpg
 
Any chance of a clearer photo
This is the diagram for anyone in the future that is having issues with gauges or dashlights. Make sure your dash casing is grounded. Use a testlight and make sure its not getting power. Also in this diagram that pin thqt looks pink is NOT A PINK WIRE IT IS PURPLE!! If this helps anyone give me a like so I can be even more popular.

View attachment 1413277
 
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