Want LED light to go off when car starts

1. Take off the panels under your dash and find some wires
2. Use a continuity tester to find a wire that is hot only when the key is on
3. Splice this wire and run it, along with a ground, to terminal 85 & 86 in a relay
4. Find a constant power source (one that is hot all the time) and run it to terminal 30
5. Run your LED off terminal 87a
6. Marvel at how simple it all was

Connect the light e. diode pointing (positive end) to a hot wire. The other end (negative) to a resistor in series to a component in the car that goes ground when ignition is off. One example found on a Honda is the clock. When ignition is "on," a terminal in the connector goes positive. This terminal goes to the negative end of the light e. diode. Confused? see below:

I dont get it, what does the resistor do?

NM, I just googled, I get it.

Or don't even bother with a relay: connect the + side of the LED via resistor to the + of the battery, connect the - side of the LED to the + of the coil or wire from ignition switch.

When the ignition is off the LED will ground through the ignition system or radio or turn signal or other system that gets it's power from the ignition switch. When the ignition is on the LED will have both connections at 12 volts and will turn off.

Hope this helps, Peter

p.s. there are a very few cars that this will not work on when the points are open the LED will not turn on, but most will work well.

May I ask why?

If you are deaf and need some positive indication that the engine is running, the oil light is an option. With the ignition on, but the engine off, it will be on (if it is not, check the bulb). Along the same lines, the battery warning light is okay, but it will also come on in some situations, while the engine is running (failed charging circuit).

he wants to spend all kinds of money to make his car "look" like it has an alarm, when for $20 he could buy this exact effect from any tint shop, or car parts store, to each his own....

punch

I've seen quite functional alarms with the LED for not much over $20 in discount stores. In fact, I bought a new Ungo (Clarion) to add to the keyless entry system of my Ford for under $20 last month on Ebay. I guess folks aren't buying alarms as much now that alarm / remote start units are so popular and cheap.

PoD