Question about wiring marker light/turn signal

[72 swinger]

I recently put a 70 dart grill in my 72.

I can get the turn signal to work by itself and parking light to work by itself. But when parking lights are on and you try to put signal on it does not work.
I also noticed the bulb in the socket only lights up one of the elements (small one) in the socket. Both should be lit when lights are on and turn signal is on.....rite? Any help would be greatly appreciated.

[email protected]

516 359 7734

Thank you,
Chris

 

[slantsixdan]

Sounds like crossed wire(s) and/or a faulty or (probably) missing or faulty ground. There are two filaments in each bulb. Bright for turn, dim for parking. There are two base contacts on the bottom of each bulb; one of them is the feed for the bright and one is the feed for the dim. Both filaments ground through the metal shell of the bulb base. If the ground is no good, the bright filament will ground through the dim filament. Result will be turn signal dimmer than it should be, with slow rise from off to on, and often an improper flash rate. When you turn on the parking lamps, then the dim filaments are no longer a path to ground and then the signal won't work at all. So, make sure you've got a good ground at both front park/turn bulbs.

 

[RedFish]

When the park lamp grounds through the turn signal circuit it will light the dash turn indicaters too.