1971 right side markers dim when lights on | Ford Thunderbird club group 1955-2005 T-Bird models

1971 right side markers dim when lights on

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Thunderbird Year
1971
On my 71 all of the stop and turn signals work correctly when the headlights or parking lamps are switched off. When switched on the right side marker lights go very dim. At this state the front and rear turns work but the rear turn doesn’t sequence although It sequences normally with lights off. With headlights switched on a press of the brake pedal instantly lights the left brake lights as it should but the right instantly sequence once until on.
when the headlights are on the right signal indicator is illuminated which tells me the normal path is interrupted.

I’ve studied the heck out of the schematic I have and it’s simple but omits what goes on inside the sequencer and column switches. I’m unable to see visibly and understand how the circuit is completed with the park lamps powered. Really scratching my head. Could use some tips.

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The 1971 side marker light wiring is unique to the 1970-71 Thunderbirds, 1970-71 Lincolns, 1970-71 Cougars, and 1970 Mustangs..
The side marker bulb ground path passes through the front turn signal bulb element.
This arrangement causes the side marker lights to flash in unison with the turn signals, until the headlights are turned on.
With the headlights and/or running lights on, the side marker lights flash the opposite of the turn signals and
the bulb current flows the opposite direction.
Note: non-bidirectional LEDs will not work in the side marker sockets because of this reverse current flow.

If the ground path through the front turn signal element is bad, it could cause the side marker light to glow dimly.
It will also affect the sequencing on that side.

Verify that the front right turn signal bulb socket is grounded and has the correct 1157 bulb installed.
If front LEDs have been installed, an LED side marker adapter kit (D0WY-15A434-LSM) must be installed for all 4 side markers.
This kit redirects the side marker light ground.
 
cougarsunlimited said:
The 1971 side marker light wiring is unique to the 1970-71 Thunderbirds, 1970-71 Lincolns, 1970-71 Cougars, and 1970 Mustangs..
The side marker bulb ground path passes through the front turn signal bulb element.
This arrangement causes the side marker lights to flash in unison with the turn signals, until the headlights are turned on.
With the headlights and/or running lights on, the side marker lights flash the opposite of the turn signals and
the bulb current flows the opposite direction.
Note: non-bidirectional LEDs will not work in the side marker sockets because of this reverse current flow.

If the ground path through the front turn signal element is bad, it could cause the side marker light to glow dimly.
It will also affect the sequencing on that side.

Verify that the front right turn signal bulb socket is grounded and has the correct 1157 bulb installed.
If front LEDs have been installed, an LED side marker adapter kit (D0WY-15A434-LSM) must be installed for all 4 side markers.
This kit redirects the side marker light ground.
Click to expand...
I’m very grateful for your input on this. I have the cougars unlimited sequencer and led tails and have been happy with them. Only the tails are led to clarify. I got the impression from the schematic I have that the ground path had to go through a lamp if not something latent to the drawing. The front turns both work perfectly with and without park/headlights. So far last weekends go at it I cleaned two grounds at the front corners of the engine bay. Pulled all the lighting connectors apart to inspect for corrosion in the engine bay. I swapped all the bulbs from right side to left and got no improvement. I will dig deeper into the front corner and report back.
 
That schematic leaves a lot to be desired. It doesn't necessarily reflect the correct wire colors either.

I had a similar problem on my 68, and when I replaced my headlight switch to resolve another problem the turns signals started to work correctly. So I would start here, since that appears to be a common element for both the headlights and the signals. Be aware that there were at least two different headlight switches for the 68, and I don't know what carried through to 1971. The 68 switches also controlled the vacuum headlight doors, which the 71 doesn't have. In 68 the new replacements are the "short stalk" variety, the stalk being what the headlight knob attaches to. My 68 just missed that regarding date of manufacture, and uses the long stalk variety. I found this out the hard way. I know one person that replace a long stalk switch with a short one, and just shortened the stalk. I opted for a used long stalk switch (not available as new) and had to get a couple before everything worked. All is good now.

Steve
 
That schematic leaves a lot to be desired. It doesn't necessarily reflect the correct wire colors either.

I had a similar problem on my 68, and when I replaced my headlight switch to resolve another problem the turns signals started to work correctly. So I would start here, since that appears to be a common element for both the headlights and the signals. Be aware that there were at least two different headlight switches for the 68, and I don't know what carried through to 1971. The 68 switches also controlled the vacuum headlight doors, which the 71 doesn't have. In 68 the new replacements are the "short stalk" variety, the stalk being what the headlight knob attaches to. My 68 just missed that regarding date of manufacture, and uses the long stalk variety. I found this out the hard way. I know one person that replace a long stalk switch with a short one, and just shortened the stalk. I opted for a used long stalk switch (not available as new) and had to get a couple before everything worked. All is good now.

Steve
 
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