Hello. I have a LR turn signal /brake light that is dim. I’ve checked the ground and it’s good. Right side is nice and bright. Odd thing is the power is feeding back into my dimmer switch for the headlights .I have a lighted push button dimmer switch on the dashboard . With the lights off when I use the left turn signal the dimmer switch blinks faintly to the rhythm of the blinker. Don’t understand how this is happening as headlights and turn signals are on their own separate circuits. Any advice on how to diagnose this issue would greatly be appreciated
There is a ground problem; turn signal is feeding back thru the tail light filament. Could be housing to mount, bulb socket to light housing, bulb to bulb socket, or odd chance but internal to bulb.
and it could be at a different light bulb than you're checking....bad grounds do very mysterious things!
Bad bulbs will drive you insane and do all sorts of weird crap. Swap them side for side, see what happens. Nothing wrong with having a few spares around.
The bulb you have has blown and the blown filament is touching the filament that is still intact. I had the same issue with a car one time, step on the brakes and it would feedback through other lighting. Replace the bulb and you will be good.
You said you checked the ground, but did you check it visually or electrically? Visual checks may show shiny surfaces, but they don't verify that a ground is actually good. The best way is to get a long jumper wire, connect one end to the battery negative post and the other end to the negative lead on a digital voltmeter. Take the positive voltmeter lead and touch it to the light socket with the socket in it's normal position and the light on. The voltmeter should read between 0.0 and 0.1. Any reading higher indicates a bad ground. On a dim light with a bad ground you may read as high as 5 or 6 volts.
Its definitely a ground or bulb failure. 9.9 times out of 10 its ground! Take a wire from negative post on battery if 12v converted, Positive if 6v PG, and go back to the tail light housing and tap the wire to the housing if bare if not, touch it to the mounting stud that's clean and non painted. If that doesn't help, then pull the lens off, touch the grounding wire directly to the outside of the bulb grounding, if that still doesn't get it, then bulb is probably bad. Jumper wire method is tried and true! Let us know what you find!
As we tend to 'overfinish' many of the parts on our cars, grounding can get iffy. The factories didn't apply a lot of paint on normally unseen brackets and whatnot, allowing easier grounding paths. Powdercoating is even worse for this. So while you may have a shiny clean ground at a location, does the part you've grounded to have electrical continuity back to the battery?
Also 60+ years of corrosion will screw with things...the steel or brases tube that supports the bulb, that's pressed and crimped into a chromed pot metal housing, will get corrosion in places you can't even see.
My Ford had those wonky-multiple piece tail light sockets, even the new ones were the same construction. Those went adios and I opened the bucket holes to accept a newer GM socket, a much better ground IMO.
Shhh.. I like sitting back watching people pull their hair out chasing the wrong thing. Simply swapping bulbs around usually tells you what is going on.
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