I managed to snag a Blaupubkt RPC430 stereo cassette player from a 1992 240 with factory mounting plate and plug. My 1990 had a gaping hole where the top-mount radio should be, but still featured door speakers, factory speaker wiring, and volvo amp behind the glovebox. I did not want to put a pricey CD/MP3 player in this car since I can use the cassette adapter to hook up my iPod. I was trying to find a stock CR712 but nobody was selling.

After a little testing with my multimeter I managed to determine ground, ignition power, constant power and the +/- wires to the front speakers.

I hooked up the antenna and installed the radio in the dash, but no sound comes from the front speakers at all. It receives and I can tune it and set stations, but I get no hint at all of sound from the front speakers. I used my multimeter to read approx 3.5 volts to the speaker wires at the harness plug as well as at the wires to the speakers. Seems right, but still nothing. *Is* that right/normal?

Notably, I had to rig up a harness plug, by stealing the female end from one of my junked 740 radios. Wiring color are all screwy looking but it does plug right. I checked several times, but I may have something wrong here.

I'm posting such a mundane question in here because I am unsure if the remaining volvo amp is causing problems. I'm also unsure if the rear speakers require the amp to work - the four rear speaker wire plugs jack to the amp.

This sort of thing should be pretty easy for me (or anyone) to wire up, but I'm stumped. The only thing that I could have messed up would be reversing the +/- wires to the speakers - but as I understand it, that shouldn't really make a difference.

Any thoughts?