Older systems were about 1 volt. Newer systems can go all the way up to 6 volts. It is diffucult to measure with a voltmeter. At normal volume the signal will only be 0.1 to 0.5 volts.
The best way to test a system is to plug a discman into the input of the amp. If you still get no sound, check your "Remote" turn on wire (it's usually blue).
It's a bad idea to use home equipment in a car. Home equipment is built differently. I blew the output transistors on one of my home amps while testing a car audio system.
Now I use a boombox with a line input.
<<Edit>> Actually, I should say I use one of these...
RadioShack Mini Audio Amp For $12 you can't go wrong.<<Edit>>
BTW, you need your meter on the "AC Volts" setting to see anything.
HTH,
BP
