Hi Lew,
I've been thinking about your signal lights for a bit (had a few problems with
mine, too!). For starters, I found it helpful to find out how the signal flasher
works: when you put 12 V across it, the current flows through a resistor wire
that heats up, develops a bit of slack to allow a curved membrane to snap into
a position that interrupts the current. The wire then cools down, the membrane
snaps back into contact position and the sequence starts again. The more voltage
you put across the flasher, the quicker the wire heats up and the quicker it
flashes. My flasher goes crazy when you short it to earth, when it gets the full
12 V. If you have a couple of bulbs in the circuit, you draw less current and
it slows down.
> The signals work rather languidly with the key on but fail to blink when
> the parking or headlamps are on. They do burn brightly but don't blink
> (emergency flashers work fine).
If they burn but don't blink it is because of a slight voltage drop across the
battery with the headlights on? The flasher of course shouldn't be quite
so sensitive to battery voltage.
> Trying, w\ headlamps off, to get a zippier
> flash by bringing a test ground wire from the batt. neg.directly to the bulb
> case doesn't seem to help.
This makes sense since your hazard lights work - the circuit from the bulbs
to earth is the same for hazard or signals (at least it is on my '69 model -
I tried to compare the '69 and '75 wiring diagrams but gave up...)
> Extended time with the signal on while testing
> causes them to fail entirely and then it won't blink no matter what I do.
I feel this can only be because of a fault in the signal flasher - the rest of
the circuit is stationary and doesn't 'change' when you leave it on.
> They all click
> snappily when energized on the bench w\ a 12v M.C. battery. but If I hook up
> a 12v. bulb in the circuit they won't flash, nothing happens?
Do you mean the test bulbs don't even burn? If so, get rid of the flashers is
my advice. When in 'resting' position, you should have contact across the
flasher and that should make any bulb burn. If it is a low Watt bulb, it may
not flash but should at least burn.
You say the hazard flasher is OK, and you don't mention different action for
left or right signals, so it seems your bulbs are the right kind (21 Watt on
my B). Summarising, my guess is that the flasher is at fault since you get
fairly normal operation with key on headlights off; that indicates the rest
of the circuit is OK. I didn't get a grip on my electrical problems until I
ran a few xerox copies of the wiring diagram and traced the relevant parts of
it in pencil with the appropriate colour... The diagram is a nightmare.
Hope this is of some use to you...
Frank van Dalen
'69 B
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