Hi, I am adding a third brake light to my 71 Riv and when I hook it up the lights are really dim. It uses LED lights so I would think it would use less power. I used vampire clips to pull power from each tail light wire (yellow and dark green) and hooked it into a control box that is supposed to keep the 3rd light from flashing with the blinkers. I jumped the brake light switch with a piece of wire so that they stay on. With my DVOM I check the voltage at the tail lights and I get 9.8 volts. The battery is putting out 12.4. I pulled the connector near the trunk hinges on the driver side and I get 12.3 volts. However, as soon as I plug in the tail lights and back-probe the connector it goes back to 9.8 volts. The taillights shine brightly, but for the LED unit, it just isn't enough voltage. My battery is a little weak, but the car starts fine, and everything should still work with over 12 volts. Could the load of the taillights cause the voltage to drop 2.5 volts in that circuit? My wiring diagram shows two other connectors between the steering column and the trunk. Does anyone know off the top of their head where these other connectors are?
sounds like one that i messed with acouple years back. the diode system that is supposed to integrate it was dropping voltages a little more than i expected. what i ended up doing was running a single wire (i used 16 gauge) directly from the brake light switch to the third brake light. the only drawback was that when the emergency flashers were used the third brakelight stayed off.
Maybe I will try that. I checked it again and I have 10 volts under the column with the tail lights on. So I must have a leak somewhere under the dash. I don't know where the wires go after they go behind the fusebox. Their is a 12volt power for the sail panel lights at the rear connector. I was thinking of putting cheap relay in and using the brake lights to trigger it and pulling power off that other circuit for the third light.
