Technical Turn signal indicators in dash both come on when I use the signals, what's wrong?

I got a 56 Cadillac here that the signals were working fine. Now all of a sudden both indicators in the dash work whenever you choose left or right. On the outside of the car everything is working as it should. I checked grounds on all the sockets and everything seems fine. I know it's back feeding from the front somehow but I just can't figure out what, Anybody have any ideas?

 

Do they light when you turn on headlights?

 

Nope

 

that rules out broken filament touching other one

 

As stated above everything else works perfectly as it should it's just the lights in the dash that are acting up. Brake lights work the outside signals work fine dash lights work. I even have an extra turn signal switch that I hooked up and I works just the same so it's not that unless I have two junk switches

 

http://www.oldcarmanualproject.com/tOCMP/wiring/5765wiring diagrams/Cadillac/MWireCadi65_3WD-034.jpg
1957 found, expect 56 is very similar.
Dark Blue (right side) and Light Blue or Blue (left side) from switch connector are widely separate circuits. I'd check first at that connector and the TS switch, then the Black wire from each indicator to the flasher. Both indicators use this circuit and are tied together.

 

Have you changed the flasher out recently?

 

Do the dash indicators flash in the same sequence with the outside signals, or are the indicators alternating ( signals go out, indicators go on)

Also, what happens if you activate the 4 way flasher? Or hit the brake pedal with the turn signal on?

 

Chased all the wires and everything is working as it should but when I put the test light to the black wire of the Flasher the lights in the dash work backwards but separately. I swapped the Flasher for an original one I have here at the shop and now it's working perfectly. The one that I took out says made in China. That ****ed

 

Thanks for posting the outcome, too many ask questions and never post a resolution!

 

This sounds like a cl***ic loss of ground problem. You said you checked the grounds; did you use a meter? How did you actually check them?

If you have a digital volt/ohm meter, you can easily check the grounds electrically. Set the meter to read DC volts and connect the black lead to battery ground (at the battery). You can use a jumper lead to accomplish this. Now turn on the flashers so that the problem is present. Touch the red lead to the light socket base (check each socket base). The voltmeter should read 0.1 volt or less signifying a good ground. If it reads more than 0.1 volt, you have a bad ground. It is a quick, easy test and if verifies the ground.

 

You posted the fix while I was writing this. Thanks for letting us know.

 

I've heard that a "four way" flasher is made different, but looks the same as a turn signal flasher. Don't know if that would cause your problem. Anyone know of this being a problem?

 

Glad it was something simple, you could go crazy chasing electrical gremlins. I'll file that away as the first thing to check if I ever have turn signal problems.

 

I know you've already resolved your issue but I'll post this in case someone else searching the internet for turn signal problems/solutions stumbles on it.

I had a similar issue on my '57 Chevy, the turn signals on the dash would both light up but also the front parking lights were out.

My issue is my parking light housings ground to the grille bar, which grounds through the aluminum grille insert, to the inner fenders/bumper splash pan and then to the rest of the body. The ground from the bulb to the bulb housing was fine, as was the ground from the housing to the grille bar. But no current was getting from the grille bar through the grille to the inner fender. The fix was as easy as adding a ground jumper wire from one of the studs on the grille bar to the inner fender, eliminating the need for the mesh grille insert to have a clean path to ground.

Seems simple, but it's not something I ever would have thought of.

 

it is a Cadillac, the Standard of Excellence... the car was pissed you put China parts on it.

 

Hell I've had tons of problems with flashers lately. Even getting them locally. The 550 three-prong flasher not one parts store in my area has one in stock so the customer bought one from Amazon or something and that's the one that was from China. I had a old GM one from some wiring harness I cut out of a car that I tossed in there

 

I’m starting to feel better about all of the silly old parts I’ve squirreled away all these years.