So drivers travelling in the opposite direction know you have an intention to cross their lane.
You only need to check youtube to see drivers who don’t see cars in other lanes or those who don’t use the indicators (don’t know how to use, don’t know they are fitted...)
What you're trying to do is overly complicated and you would need an actual auto electrician to implement. Without knowing the technical details of your particular vehicle, you won't get a straight answer. But I can tell you it varies between manufacturer and you have things like body control modules and multiples CAN buses to contend with.
When you say '...
What Mike said and also:
On the highway; letting drivers in front of you know that you're switching lanes. That way they know that you're about to overtake them
When parked, oncoming drivers as well as drivers parked in front of you know you're about to drive off, so they know not to overtake or drive off.
When leaving a roundabout, oncoming drivers know ...
Sounds like a poor ground, when the headlights are off then the 21W can get to ground via the headlamps but if the headlamps are on then that does not happen.
Check the ground connections and for breaks in the ground wires.
Without a turn signal on coming drivers would not know if you are wanting to make a right/left hand turn. This would reduce safety if turn signals were not a thing. In other words its a form of communication with other users on the road.
Based on the shape of the "special nut" which is certainly an unusual part name, I would expect that the nut is really a rivnut. When installed, the tool pulls the portion inside the sheet metal, compressing the back side against the metal, preventing the spinning you're experiencing.
There's no documentation to support this, but it seems unlikely ...
Headlights come in good/better/best.
One thing to watch out for is the expected hours on headlight bulbs. "Good" often has a normal expected life... but the "better" or "best" bulbs actually have a much shorter expected life. Read the package labels carefully.
The vibration and thermal extremes of vehicles is a rough location ...
There are longlife lamps available. They are a bit dimmer than the standard lamps, but it isn't unheard that they outlive the car.
On my 12 year old car car both headlights got replaced with some noname H7, one brake light broke after an collision. The other lamps are original and in working order.
It would be a waste of money for the manufacturers to use ...
I have fitted a brand new incandescent and it has blown after seconds...
I have fitted other incandescents and they last longer.
manufacturers give information called "Mean Time Before Failure". This is an estimate of the expected life, but some will fail outside of this time.
While manufacturing processes and materials make the LED type of lamp ...
Headlights and fog lights have a parabolic reflector that is shaped to shine in a cone ahead of the car, the light source has to be in the right position to focus correctly. Think of a magnifying glass, as you move it closer or farther away from a light source the focus changes, the same principle applies here. Most likely the LED replacement is shorter or ...
The problem was an unplugged cable under the scuff plate in the trunk.
It's quite easy to take out, you just have to remove the trunk floor and pull that part.
There's only 1 cable connected to that little panel and it wasn't connected.
Make sure you hear the click when you connect it.
Most likely there is a short circuit somewhere in the tail light circuit in the trailer's wiring, which will be causing the car's fuse to blow.
To test this, get hold of a digital multimeter (a cheap DIY shop one will be fine), and set it to continuity mode. With the trailer not plugged into the car, Take the bulb out of the right hand tail light, and test ...