How to test wires

[marlcam]

I wish to determine which wires are for what in my dashboard stereo area.

 

Among the wires, there are two yellows. According to the schematic, one is left rear speaker negative, one is switched from ignition. I am trying to test for power with a multimeter when the key is in the accessory position. I'm not getting anything. I need advice on the multimeter set up to read this DC amps.

 

Does anyone have a better way to figure out which wire is which?

[bdox]

First, set your multimeter to the closest setting, but not lower than, 12v DC. Touch the black (negative) probe to a paintless metal surface, then touch the red (positive) probe to the wire. If you've got the car on Accessory/Run you should see 12v from your switched wire.

[bossier62guy]

a wiring diagram would be the best option in my opinion but the method stated above will work nicely if all you're looking for is power.

[marlcam]

Thanks. I've tried that but I guess I'm messing up with the multimeter. Perhaps I'm not getting a good ground. I'll test it on a taillight or something I know.

[waumo1]

Thanks. I've tried that but I guess I'm messing up with the multimeter. Perhaps I'm not getting a good ground. I'll test it on a taillight or something I know.

 

Good idea. Always verify your test equipment is working and you know how to work it.

 

You said you needed to test amps. You want the meter set to volts like the previous posted said. If you already tried to test voltage with the meter set to amps (current) you may have blown a fuse in the meter and need to check that out. Could explain why your meter is working.