[dv657172]

High Beam Indicator Light at the top of the dash is lit up when headlights are on Dim setting and isnt lit up when the Brights are on. Original factory wiring harness.

Ground issue, floor dimmer switch issue or something else?

[Scarebird]

Are the actual head lights working correctly?

[OG68]

My initial thought is that the headlights are mis-wired or installed in the wrong location. Just to be clear, Outside headlights have three terminals, inside lights have two.

I'm assuming that no wiring modifications have been done that you're aware of and the car is equipped with non LED headlights.
Has it always been this way or has there been any recent replacements of the high beam switch or headlights? Firewall plugs removed? Accident repair?
Even though it has the factory harness a lot of things could have been modified in the last 52 years.

High beam and and high beam indicator wire colors are Lt Green. Low beam is Tan.
The high beam indicator is wired together with the dimmer switch high beam wire at the firewall connector plug behind the fusebox.
Schematics on the next post.

These are basic steps to verify proper operation of the headlight circuit.
You first want to verify operation of the dimmer switch. If ok then move on to the next step

1. Check the Lt Green wire at the dimmer switch for 12 volts when the high beam indicators is on. and that the tan wire has 12 volts when the high beam indicator is off. The blue wire is common to both and always has 12 volts when the headlight switch is pulled out all the way. The plug can only go on one way




If readings are correct;
2. Check the inside headlight plugs for Lt Green/blk tracer and black wires (2). The outside headlights have three wires Tan, Lt Green/black tracer and Black
If not good, make sure the plugs are on the right headlights and / or the headlights are mounted correctly.



If good,
3. Verify all four headlights are on when the indicator is on.

If not good,
3. Pull the fuse box off the firewall on the interior side and check the terminal block. Make sure the lt green wires from the indicator light and dimmer switch are on the same terminal.



If you haven't found the problem there may be problems with grounds or lack of. The firewall plug may be mis-wired on the engine side. The instrument panel plug may also be mis- wired.
But try the basic steps first.

[OG68]

Schematics attached

[dv657172]

Thanks for all the info and advice OG68! I will be definitely looking into all that tomorrow and report back.

[dv657172]

Only a limited amount of investigation thus far but

Low Beams are outboard (3 prong connection)
High Beams are inboard (2 prong connection)
Both of which work fine as does the floor dimmer switch...but dash indicator comes on in wrong sequence (light ON when Dim lights on, OFF when brights are on)


I haven't seen any wiring that has been modified thus far

I have had the car for years but never noticed issue until recently as I have been going through all the cars interior and exterior lighting for proper operation

[Scarebird]

This is a 1972 OEM Shop manual; same as the 71 but in color (I have both). I highlighted the wiring - all I can easily see going wrong is the feed wire from the indicator going to the wrong cavity in the fuse block. Problem is IIRC the 2 wires are crimped together, so unless the harness was modifed that should not be an issue.

edit: unless I am seeing things, the schematic for the switch is in error - the light blue wire (power) should be the "hinge" terminal, not the light green wire.

[Scarebird]

OG68's pic shows this junction well:

[OG68]

[QUOTE=Scarebird;6458136]
unless I am seeing things, the schematic for the switch is in error - the light blue wire (power) should be the "hinge" terminal, not the light green wire.

You're not seeing things. They fubar'd that one.

Correct on the 71 drawing though

[OG68]

Originally Posted by dv657172

Only a limited amount of investigation thus far but

Low Beams are outboard (3 prong connection)
High Beams are inboard (2 prong connection)
Both of which work fine as does the floor dimmer switch...but dash indicator comes on in wrong sequence (light ON when Dim lights on, OFF when brights are on)

Check the fusebox terminals. Battery disconnected first.
Remove the two screws holding the fusebox to the firewall and then unclip the fuse box from the terminal board.

If their headlight wiring is correct then the only other alternative I can think of is the firewall plug is mis-wired. Wouldn't surprise me if its been that way since new.

[OG68]

Originally Posted by dv657172

Only a limited amount of investigation thus far but

Low Beams are outboard (3 prong connection)
High Beams are inboard (2 prong connection)
Both of which work fine as does the floor dimmer switch...but dash indicator comes on in wrong sequence (light ON when Dim lights on, OFF when brights are on)

Check the fusebox terminals. Battery disconnected first.
Remove the two screws holding the fusebox to the firewall and then unclip the fuse box from the terminal board.

If the headlight wiring is correct then the only other alternative I can think of is the firewall plug is mis-wired. Wouldn't surprise me if its been that way since new.

[Scarebird]

Originally Posted by OG68

If their headlight wiring is correct then the only other alternative I can think of is the firewall plug is mis-wired. Wouldn't surprise me if its been that way since new.

If the wires were switched either side of the plug that would do it.

[dv657172]

Dimmer switch wiring looks correct

You tell me on the fusebox pls, are the green and tan wires switched? Light blue wire routing looks different than OG68 pic

Thanks
DV

[Scarebird]

Looking at OG68's pic - it does NOT match the wiring diagram, his or mine.

Yours does however. That said, if the wires are switched on the lighting harness plug engine side, you will get the symtoms you have.

You have the info here to sort this out now. Pull the light harness out of the fuse block (3/8" bolt must be undone) then run 12v to the green then the tan wires and see what lights up.

[OG68]

Like Scarecrow said, your wiring matches a 71 terminal board. Mine is a 68 so will be slightly different. Since the interior side looks good, pull the right side plug off and verify the plug side wires match the fuse box side.

[dv657172]

Pulling off the engine side of the fuse box appears pretty difficult given the power booster....given the wires are definitely correct at the headlights and appear correct as per the schematic going into the fuse panel on the interior side is there anything possible other than the wires being backward at the fusebox on the engine side? if not, then what is the solution to fixing the issue, switching the wires on the fuse box (interior side)?

[Scarebird]

You could switch the wires further down the harness by cutting an soldering - not recommended.

Pulling the harness plus is not difficult if yyou have a 1/4 drive ratchet. You will also need a plug tool.

Or just live with it, no harm done.

[dv657172]

Scarebird

I meant difficult in terms of accessibility given the Power Booster. I have been spoiled with manual brake 65 GTOs which have a bit more space to work on everything

What is the plug tool you referred to?

[OG68]

Small flat blade similar to a 'tweaker' screwdriver. Releases the terminal locking tab inside the plug housing. Takes a few seconds to switch the wires.

[Scarebird]

yes, these are them:

https://www.amazon.com/Lisle-57750-W...389673975&th=1