V1 Ambient light sensor check-up

[Ark :D]

My ambient light sensor does not seem to work, so I figured I would check with you guys to verify what I am seeing with it, electrically speaking.

Voltage to sensor with ignition on: 5v
Resistance on the two pins on the sensor itself: 12k-15k ohms?

Does that seem right?

 

[ctuinstra]

Does the resistance change with light? I haven't really dug into exactly what type of light sensor it is.

 

[Ark :D]

I'm not sure to be honest, I just tested the resistance with it disconnected. I'll try to find out tomorrow.

 

[Desert Sasqwatch]

Depends what type of light sending device it is, a photodiode or phototransistor. The photodiode uses light to create an electrical current in the device - don't believe the 'smoked' plastic in the one used would be conducive to this type of device. The phototransistor uses light to provide bias to a transistor to allow current flow through the device from a supplied known voltage/current. Believe this is the device used in our light sensors, since it has 5 volts on it normally.
If standard transistor, the base is the light sensitive part of the transistor, with 5 volts applied to the collector in low light the emitter should have almost no voltage. In a light source there should be voltage (3.5 volts or more?) at the emitter. Be careful checking, since these devices work on very low current - typically 100 to 300 milliamps.