Could be the turn signal switch - could also be an open ground at
one the left-side turn signals, either the lamp-base to socket ground
or the wire from the socket to chassis ground. This is far more
common when you have a dual-filament lamp like the old 1034/1157 (or
the new wedge-base IIRC 3157) that has a bright 'turn' filament and a
dim 'marker/tail' filament in one bulb.
The power from the left signal goes through the 'turn' filament of
the lamp but can't get to ground - so it goes through the left
'marker' filament of the same lamp and into the marker light circuit,
across to the right marker lamp filament and lights it up, and then to
the ground for the right lamp.
Can also happen this way (both sides blinking) if they use a small
separate side-marker light on the fender with one filament that is
wired *between* the Turn and Marker circuits on each side. These are
the ones that normally blink on in sync with the turn signals during
the day, and blink OFF in sync with the turn signals at night...
They count on one side or the other being off and grounded through
the dark filament for the small side marker lamp to light, and if both
have power at the same time the light goes out. Same symptom
applies, if the ground is open on one side the power will sneak across
to the other side to find a ground there.
One of the oddities from the way they wire cars.
--<< Bruce >>--
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