1964 gto turn signal
 

Going crazy, put in new wiring harness from m/h electric, everything works well, except the turn signal indicator in the dash, 64 only has one indicator for both sides, going right works fine, going left (nothing) indicator does not work,. Anybody ever had this problem with a 64

This single light bulb depends on the ground and resistance of the lamps [bulbs] in the front and back. If even one is out or missing it will not work correctly. LED lamps also cause this if they don't have a resistor built in. Be sure all 4 corners have good connected working lamps.

What Jack said. If the front lights aren't hooked up the dash indicator won't work.

Electrical circuits are not my long suit.

But if I understand your question, your turn signals are working fine.

The dash indicator lights when the right signals are on but doesn't light when the left signals are on.

It might be helpful to you to take a good look at the '64 Tempest Wiring Diagrams. You can find a colorized version here:

http://forums.maxperformanceinc.com/...08#post6050308

Kudos to tempest1964 for posting it.

If I understand the Indicator circuit, the bulb is powered by way of the Direction Signal Switch at the same time and the same side as the side selected.

The ground for the circuit is provided by the wiring to the side NOT selected.

In other words, the bulb doesn't care which side/wire provides the power and which side/wire provides the ground.

To be honest, I can't figure out how the circuit could be "perfect" in one direction but "broken" in the other direction.

Perhaps, the Dark Blue circuit wiring is connected well enough to carry current when energized but not good enough to provide ground. Or conversely, perhaps the Light Blue circuit wiring provides a good ground but can't carry current.

You could trace the circuit by turning the left signals on and then jumpering the Dark Blue directly to a ground under the dash.

If the Indicator Bulb lights, you have proven the ground is "broken" somewhere along the circuit. Trace along the Dark Blue wire, grounding it along the way until the break is found.

If it doesn't light when directly grounded at the bulb holder, I'm not sure what to check next. Maybe the bulb or the bulb holder? Or maybe jumper to a grounded test light to see if the wiring can light it when the left signals are switched on or simply check for 12V at the Light Blue wire at the bulb holder to confirm the Indicator Bulb holder is getting power when the left signals are switched on.

Like I said, I'm no expert on circuits. But following the Diagram, I'm usually able to figure out how the circuit is "made" and eventually determine where the fault is.

I don't think the switch could be at fault since the signals themselves seem to be working fine.

If I'm off-base, somebody with more expertise can correct me.

Hope the Diagrams help track down the problem.

Bad grounds are often the culprit but it helps to understand the circuit in order to isolate where the bad ground might exist.

I had the exact problem. The bulb in the front right turn signal had blown. Once that was replaced, it worked. Its a dual filament bulb so even though it worked with park lights on, the second filament for turn signal had given up

I almost went nuts tracking a bad ground. The issue was the turn signal bulb housing. Where the bulb socket crimps the metal housing had corroded to the point it not longer had a connection. I had to turn it back and forth with the pair of pliers was all it took to fix it. But man did that take me for a troubleshooting trip.

But yes see what lights are working outside the car first.

Post #4 above has a really good info it it. Just go right back to the basics. The way that indicator is wired in the dash it depends on EVERYTHING else on the car that has anything at all to do with the running lamps, and the turn signals; bulbs (both front as well as rear) this includes ALL of the rear brake lights. All the housing sockets and grounds, & all the #1157 bulbs; everything has to be 100% for that one #1895 dash bulb to "light up" in both directions.


Once at the shop a car came in with a turn signal problem: the LF turn signal light would not work.

It was an older Buick so they gave it to me. I tracked down some of the wiring as well as testing the switch and the brake-light bulbs. When I got up front; the strangest thing. The car's owner had taken it to a local gas station to see if they could fix it first. And I guess somebody there started replacing bulbs, and they had crammed an #1156 bulb into the LF turn signal housing where an #1157 should have been. I guess an easy mistake to make since both of those are clear light bulbs. (The front lens on that car had the amber tint to it molded in.) I am pretty sure that I must have first cleaned all the ground touch-points as well and when I put a new #1157 bulb into the front TS housing everything thing started working just fine!

Those crimped steel housings do not last, just ask any '68 GTO owner!!!


It is very common for those sockets to become "un-grounded" from their steel housing, especially on a 50 year old car. The housing is the ground pathway for the bulb(s).

That or one of those springs underneath the 2 copper buttons will rust and crack in 1/2. And so basically you have an open in your + circuit which you cannot see. (GM used to make a little repair kit for those copper buttons and the springs.)

I am pretty sure that kit was specifically made to fix 1968 Lemans & GTO tail lamp sockets at first but you could easily use the parts from that kit to fix other GM cars as well.

Agreed! I just replaced my backup light switch and re-wired, then noticed only the passenger bulb lit (hadn't checked before working on the switch). I removed the lens cover and started wiggling the bulb and it flashed on sometimes depending on position/pressure. No cleanup of the socket would guarantee proper function, so I then ran a ground wire directly to the housing from the bumper frame mount bolt and now it works every time. Assuming these old housings will keep providing a good ground path may drive you crazy and I wasn't looking to replace the original unit and don't expect any judging on my wiring anytime soon!