voltage problem

[Andy-2e0bns]

Hi All,
Have a small problem that I need to sort out on my car. The owner before me fitted a light in the rear how ever this is cuasing a 13v supply to travel back along the negative feed when the doors are closed. Can anyone help with a circuit to prevent this.

with regards
Andy-2e0bns

[I_Daniel]

How is the light switched on ? A seperate switch or the door-switch.?
The door switch could be for a domelight or an alarm-system.
Does the car have a dome-light?

On a negative earth car - If the light that has been fitted uses it's own circuit then it would normally be from positive to a switch and then to the bulb holder. The other side of the Bulb (Globe) goes to earth. (Usually a very short wire to an earth spot)

[kbs]

Hi,

Are you measuring 13v between the 'negative' side of the bulb and ground while the light should be working but isn't?
If so, the connection between the negative side of the bulb and ground is faulty.

If the bulb works (and the door switch is in the negative lead) you should read 13v on negative side of the bulb (when the door is closed) as it is not connected to the ground (no current flowing so no voltage dropped across bulb). Just noticed '2E0'. Intermediate isnt it? I don't need to tell you about ohms law!

If the door switch is also used for an alarm (and either the alarm or the light is aftermarket), fit a dedicated switch for lamp.

Good Luck

Keith