Dash turn signals Options

[Cal]

Question.....when I turn on the turn signals in either direction both indicators on the dash board light up at the same time. Any idea what the problem might be?

[toolguy]

You're probably going to find this hard top believe, but check the wattage of the bulbs in all four corners. .
I had this happen when I installed all new bulbs. . After a couple of hours of checking grounds, connectors and circuits, I traced it down to not using the correct wattage bulbs. . Once I put in the old original bulbs the dash indicators worked correctly again.
I never figured out the 'why' of it and chalked it up to the old military electronic explanation that always applies. . "PFM". . Pure F-ing Magic. .

[Spoke]

You're probably going to find this hard top believe, but check the wattage of the bulbs in all four corners. .
I had this happen when I installed all new bulbs. . After a couple of hours of checking grounds, connectors and circuits, I traced it down to not using the correct wattage bulbs. . Once I put in the old original bulbs the dash indicators worked correctly again.
I never figured out the 'why' of it and chalked it up to the old military electronic explanation that always applies. . "PFM". . Pure F-ing Magic. .

I can take a bit of the PFM out of it for you. See the diagram below with the flasher in the top right corner. Notice the 2nd small coil.

When heavy exterior bulb currents flow when the flasher is flashing, the secondary coil connects the "K" lead to 12V. The K lead is connected to a common wire between the dash indicators.

When the heavy exterior bulb current flows, the K lead connects to 12V, thus one of the dash indicators has 12V across it and lights while the other indicator has 0V across it and is off.

2 scenarios cause both to light:
1) Exterior bulb current is not enough to close the secondary relay; both indicators flash at 1/2 voltage.

2) The secondary coil loses its efficiency over time and heavy exterior bulb current doesn't close the secondary relay.

My flasher suffered from the 2) issue. On the first flash, only the correct indicator lit, then on subsequent flashes, both indicators lit. I solved this by removing the common wire between the indicators from the K lead and attached the common wire to tach ground.

This is a common fix. If you do this fix, you'll find the opposite indicator lights. (RT indicator lights with LT side and visa versa). Swapping the bulbs and bulb holders LT to RT will solve the opposite indicator issue.

[Dave_Darling]

2 scenarios cause both to light:

You forgot one scenario:

Your early 1974 914 has a wiring harness that is only set up to have one turn signal indicator in the tach. It also has a leftover early-style tach with two arrows in it. So the guys at the factory spliced in another section of wire to daisy-chain the two arrows together so both light up at the same time.

I'm pretty sure this is the OP's issue, because he mentioned he had an early 74 car.

--DD

[Cal]

2 scenarios cause both to light:

You forgot one scenario:

Your early 1974 914 has a wiring harness that is only set up to have one turn signal indicator in the tach. It also has a leftover early-style tach with two arrows in it. So the guys at the factory spliced in another section of wire to daisy-chain the two arrows together so both light up at the same time.

I'm pretty sure this is the OP's issue, because he mentioned he had an early 74 car.

--DD

That's interesting.....is that typical? I just assumed something was wrong somewhere. All the exterior indicators and flashers work as they're suppose to. Is there anyone else with an early '74 that can verify if both tach gauge indicators come on at the same time when engaged?