Chopped radio wires. Where do they go?

Question

I bought a '90 BMW 525 with no radio. The speaker wires, ground, constant power, and ign power are easy to suss out. But there are three left how can I determine were these go?

Answer 1

You probably don't need them. But one or two of them are probably illumination wires. To test them, use your multimeter and see if either shows voltage when the parking lights are turned on. If you see voltage with the lights, adjust your dash light dimmer switch. If the voltage varies with the dimmer position, it's a dimmer wire. If it doesn't vary, but turns on/off with the lights, it's an illumination wire. Many after-market radios don't use these at all, but if there's an orange or orange/white wire on the after-market deck, connect it to the illumination wire and tape off the dimmer wire.

Another wire might be a power antenna activation wire. If you have a power antenna, you can test it by connecting the wire to 12VDC through a 1-amp fuse. You may need to have the key-switch on. If the antenna goes up, you've found the antenna wire.

Answer 2

One wire might be for panel lighting, one for a power antenna if you have it, maybe one for the security system that prevents a stolen radio being used in another car. Get a Haynes manual or a service manual from your BMW dealer.