headlights on /off

[cohammer60]

My 74 bronco had an issue when dimmer switch was pressed the headlights go off , replaced switch and got new halogen headlights with relay and harness. . After all that still same . I checked plug at dimmer and with jumper one side and middle wire turns on lights and other side with jumper seems to have dead short . Tried to trace wires and follow diagram still stumped . Thanks for any advice .

 

[Lanny]

My 74 bronco had an issue when dimmer switch was pressed the headlights go off , replaced switch and got new halogen headlights with relay and harness. . After all that still same . I checked plug at dimmer and with jumper one side and middle wire turns on lights and other side with jumper seems to have dead short . Tried to trace wires and follow diagram still stumped . Thanks for any advice .

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If any wire has a dead short and there is No fuse to burn out, then the
wire with the dead short is going to spark and smoke like crazy, and you
would surly see that.

Could it be you have a headlight wire that is not making a good connection,
or a wire that is not making a good ground for the headlight.





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[cohammer60]

Tried again but seems its just sparking . I too 2 pieces of long wire and pulled under hood while in dimmer switch plug and when touched togeather the new relay clicks but no lights .

 

[dmsfrr]

Check that the terminals in the headlamp plugs are connected to the correct bulb terminals. Look inside the bulb and the ground terminal (with the internal double/siamesed connection) should be obvious.
If the wires from the dimmer switch to the headlamps are good it's possible one of the plugs has a swapped ground connection on the back of the bulb creating a short.

There is also a hi-beam indicator lamp in the dashboard. If it's the hi beam circuit that has the problem it's wire may be damaged or somehow shorted behind or in the dash.

Check where headlight wires pass thru any body panels, there may be damage there.

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[cohammer60]

Thanks for the info , acording to the dash the bright works and dim does not . I will unplug and check as stated above and see if a plug has swapped or broken wire causing a ground out .

 

[Lanny]

Here is the way the 12 volt headlights are connected on a '65 Pickup
that I have and they have been working good for many years.


Click on picture to Enlarge

 

[cohammer60]

By looking at your headlight I believe that at some point in time my plug was changed and my ground is where you show hi beam . I will check this afternoon. That would make sense why when i click dimmer they go out . Thanks guys for responding.

 

[cohammer60]

Found short where some one had grounded low beam to side marker , thanks for all the help .

 

[dmsfrr]

Glad you found it. Thumbs up!