I am in the middle of restoring a 1970 GS 455. In assembling the instrument panel and installation, my brake light indicator is on all the time. Very dim but on. It goes to full power if I apply the parking brake. Anyone have a similar problem and know where the voltage leak came from? Key off Engine off = 0.4v Key on Engine off = 4.6v Key on Engine On = 7.3v
Where are you measuring the voltage from? With the key off, engine off there should be no voltage coming from the fuse block gauge fuse going to the instrument panel so, you might have a voltage leak coming from the ignition switch located on the steering column. You may have a second problem with the brake proportioning valve allowing a ground to go to the warning light. I have this problem with mine currently and will be replacing the proportioning valve to fix it. Here's the wiring diagram if it will help. Top diagram is gauges and bottom is idiot lights. The brake and gen lights work the same with either.
I am measuring from the brown connector on my voltage regulator. I agree with your assessment of the ignition switch or leakage coming from the steering column. I will run some tests to check that out as well as the brake voltage leak to see if I can isolate it. thanks.
