Need a bit of turn signals help

[M491Cabriolet]

1972 911: Turn signals worked perfectly until out of the blue, they stopped working. The flashers work fine. I've been trying to figure this out over time and had gotten nowhere until today (see below). I looked into the turn signal switch behind the steering wheel, the flasher unit, the obvious wiring. No issues located.

Today, I tried checking current at the fuses. For example, left turn signal switch activated, car on, ground the check probe's wire and touch tip to either side of the fuse and the turn signals start working. Put the right signals on at the switch and nothing. Touch the tester probe to the right fuse and bingo, the turn signals work. I am the world's worst electrician, so I'm totally bewildered.

Can anyone help this electrical dummy understand what I'm seeing here? Thanks so much.

[timmy2]

Corrosion at the fuses would be my guess. Moving them around even slightly cleaned them up enough to make good contact.

[M491Cabriolet]

I did that too. It's interesting because I am touching the screws next to the two fuses, not the fuses themselves. I see a tiny spark on the screw when connection is made, and voila' the turn signals begin to flash. Same deal on both sides of the car. Front and rears flash properly.

[Walter_Middie]

M491

The way the turn signals work is that there is only one flasher for both the L and R blinkers. This single flasher has power to it with the key on, and sends blinking power to both the L and R blinkers all the time - but doesn't work until the circuit is grounded. The turn signal stalk completes the circuit by grounding either the L side blinker lights when pushed down, or completes the R side blinker lights when pushed up.

Again, the flasher unit sends blinking power to both sides all the time - it's only when one side is grounded through the turn signal stalk that one side will actually flash.

I'd take another look at your turn signal stalk wiring and see if adding an external ground there makes them flash. Could just be dirty contacts.

Now that I think about it, if both sides are not working, it's most likely not the switch. I'd check for ground going into the turn signal switch. The ground looks like it goes to the turn signals, headlights, door light switches, etc.... Check to see if something else isn't working - that may be a clue as to where to look for a bad ground.

[Arctic Rat]

M491,

I'd start with changing out the flasher unit. Not expensive, easy to change and know if new one fixes the problem.

Joe D

[brianlay]

check to make sure the multi-pin round connector on the turn signal harness is fully seated.

[PeteKz]

IN addition to whatever else you are doing, use this opportunity to replace ALL the fuses. Over time, heat cycles, and humidity, the fuses age and crack, especially these olde open bullet style fuses. Sometimes you can't see the cracks until you remove them and the strips fall out. Throw the old ones away. You will save yourself troubleshooting headaches in the future. Do it every ten years.

[Simonrex55]

Originally Posted by Walter_Middie

M491

The way the turn signals work is that there is only one flasher for both the L and R blinkers. This single flasher has power to it with the key on, and sends blinking power to both the L and R blinkers all the time - but doesn't work until the circuit is grounded. The turn signal stalk completes the circuit by grounding either the L side blinker lights when pushed down, or completes the R side blinker lights when pushed up.

Again, the flasher unit sends blinking power to both sides all the time - it's only when one side is grounded through the turn signal stalk that one side will actually flash.

I'd take another look at your turn signal stalk wiring and see if adding an external ground there makes them flash. Could just be dirty contacts.

Now that I think about it, if both sides are not working, it's most likely not the switch. I'd check for ground going into the turn signal switch. The ground looks like it goes to the turn signals, headlights, door light switches, etc.... Check to see if something else isn't working - that may be a clue as to where to look for a bad ground.

Great explanation on the system!

I am in the middle of replacing a tunnel, front trunk, front headlight, Left rear, right rear wire harnesses. The harnesses are in and checking power. My flasher isn’t working, but i do have a few grounds not connected. Checking these next

[creaturecat]

ground it out. see what happens.

[spoke]

Here's the turnsignal system for a '70-'73 914. The 911 is very similar. Note the fuse for the turnsignals. Likely you've burned a fuse if the 4-ways work but the turnsignals do not. I don't know what 911 fuse this would relate to but I'd check there first.

Don't replace the flasher as if it works for 4-ways it will work for turnsignals.