right turn signal problem

Hi to everyone.  I'm new to this forum.  I recently purchased a 1978 Silver Anniversary Corvette, which has recently developed an issue with the right front turn signal.  I noticed that although the blinker was operating at normal speed, the indicator lamp was not operating on the instrument panel.  After investigating, found the right rear signal operating normally, but no front signal or illumination.  Replaced 1157 signal bulb with two new bulbs, and the flasher behind the glove box, which didn't help.  Replaced bulb in side marker/signal lamp as well.

I then checked with a test light the contacts in the rectangular plug which goes into the front lamp socket harness.  The contact on the side for the signals showed no power with the signal on.  When the parking lights were turned on, the contact then showed a steady, but dim glow, with signals on or off.  The side for the parking light was bright.  I then probed the blue wire for the signal light with the test light before it enters the plug, and there was still no indication of power when parking lights off, and dull glow when parking lights were on.  When parking lights on, right dash indicator arrow glows dull as well.  I assume at this point I will need to open the sheath around the harness along the front of the engine compartment and go from there to look for a ground or wiring issue, or could it be the signal switch itself?  Left side turn signal and running lamps working normally.

I know it's a long explanation, but thought is would simplify the diagnostic process.  Thanks, Gary

Do the brake lights work properly? Also...by chance does the right front sig come on when you mash the brake pedal?

btw...if you need the wiring diagram(s) for your car, you can view and/or download them from my web page HERE.

I have inadvertently discovered the signal issue with my C3.  It is a loose connection from the dark blue wire at the "harmonica."  The connector had been hanging under the instrument panel, and I noticed the bracket for it at the steering column.  Once I installed the harmonica into the bracket, the turn signal indicator light came on.  Upon checking the front of the car, the side marker was flashing, but still no signal light.  After cleaning and reconnecting the connector to the signal lamp harness, the bulb began to operate normally.  So there were two issues with the turn signal wiring.  I will need to open up the harness and fix the wiring issue, as the turn signals operate intermittently when the wire is wiggled.  Just happy I don't have to replace the signal switch