1974 Coupe, no brake lights, no turn signals
 

My 74 has had the power antenna removed. The wires were cut and left hanging. Would this have anything to do with my lights not working properly, like maybe a ground or something ?

Who installed the power antenna since it was not an option for 74? You may want to trace the wiring and determine where they took the power for it.

I have no way of knowing who installed it or if it was an option in 74. If it were an option would it have anything to do with the grounding of the rear lighting if it were wired correctly ?

Do you have a meter?
 

For the brake lights check that the fuse is good and that you have power on both sides of the clips that hold it in.
Do your hazards work?
Next check for power IN and OUT of the brake switch.

The Directional signals are protected by the DIR SIG BACK UP fuse.
Check that one and post back.

My bet would be that the grounding wire[s] for the rear lamps are corroded/damaged/missing. As mentioned, check the sockets for 12 volt power when turned ON. Also check for continuity to chassis ground from the bulb housings or ground pins.

My tail lights work as they should. I have no voltage at the turn signal fuse, no hazard lights, and no back up lights. the turn signal indicator arrows dont light up either. Brake light fuse is good, power to both sides. I have power at the brake light switch but I didn`t check the switch. It is a new switch but I will check it tomorrow. Since the tail lights work shouldn`t that show the ground is ok ? where would the power to the fuse come from on the turn signals ? I`m really lost when it comes to electricity

What about "grounding" do you not understand? For a circuit to work, current has to flow thru the power wire to the device (or lamps, etc). But, that alone won't make ANYTHING work. It then has to flow back to the battery thru the ground wiring. If either the power wire or the ground wire are compromised, nothing works!

Thank you for impute. I already stated I know very little about auto electric

Step by step...
 

I agree that grounds on a C3 are a big problem.
Since your tail lights work I'll guess that the main ground wire attached to the left rear of your frame is good.

Do you have a meter or a test light?

Let's work on the brake lights first.
Check for power in and out of the brake light switch.
After that check for power going into the harmonica switch at the white wire.

Follow Mr. Willcox's diagram and Mr. Shea's diagram for the colors in the harmonica switch.

Power for the brake and directional signals first go into the harmonica connection and back down to the brake lights and turn signals.

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Thank you Peterbuilt and Wilcox for this information. This will help a lot. I will get back later today I plan on spending the whole day working on this. The lights are the only thing preventing me from driving the car. Thank you again. Joe

Had to take a brake but I have made progress. I replaced both flashers, cleaned the prongs that hold the turn signal fuse. I also found a wire in the harmonica connection ( the white one) that may not have been making a good connection, fixed that and now I have brake lights and turn signals on the left side. the hazard lights now work except for the right rear. I`m 71 years old and when I do finish this I hope I never have to get under that dash again lol. Next I will trace the green wire back to the right tail light. I have 12 volts on the green wire at the harmonica connection. I will also check the ground at the bulbs.

Great job of troubleshooting!
I had the utmost confidence that you would figure it out.

One more 'ground wire test'.
The BLACK (ground) wire inside the light sockets can disconnect from corrosion and will look good even though it is bad.
Attach a wire to a good ground and touch the other end to the brass part of the socket and see if the lights work.

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All lights now work as they should. Today I traced the green wire back to the tail lights. where I only found 6 v at the light. I tried the grounding at the base of the bulb and no change.But since the tail lights worked ok I figured the ground must be OK. So what I did was turn key on and engaged
the right turn signal, set up a mirror so I could watch the tail lights and started tracking the green wire. Just about where the frame ends it looks like someone replaced the wiring harness at that point. They spliced the wires and the green wire was just barely hanging on. when I touched it my turn signal came on as well as the brake lights all is well now. And I went for a drive. ( love my Vette) Thank you all for your help.

Good job!!

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