Left Blinker Issues
1. If you have a bulb in the socket the rear blinker works, but the dash indicator does not and nothing in the front.
2. If you take the bulb out the rear blinker still works and the dash indicator works.
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Sorry but this makes no sense........you take what bulb out of what socket?
Let's review "how this works"
The signal switch only has so many power inputs, all separate:
1....brake light power from the brake light switch, anytime the brake pedal is pushed
2...full time power from the hazard flasher which is separate
3...Power from the TS flasher when the key is in "run."
OUTPUTS
4....left rear stop/ turn
5....right rear stop/ turn
6....left front turn AND DASH INDICATOR
7....right front turn AND DASH INDICATOR
GROUNDING. Not only must the bulb have a good connection to the lamp shell, the lamp shell then has to have a good ground to the body. This varies from model year. Some years have dedicated grounds connected to the lamp shell and a jumper to the body. GOOD TO ADD if you don't have
Bulbs...........SEVERAL things can happen to bulbs. The filaments can get stuck together causing interesting "cross" talk. Some guys quickly check the bulbs and think they are good when one filament might be bad. THESE ARE ESSENTIALLY two bulbs in one. BEST WAY to test them is to LIGHT them in a spare/ junk socket --which you should have for a test device, anyhow-- across a battery