I have a JVC KD-S640 (40W X 4, CD, AM/FM). I'm trying to install it in my 1968 Buick Skylark. Before I took the JVC out to the car, I traced the wiring harness and powered it up using a 12V DV power supply. The lights came on, and after a few seconds it shut off even though the power was still connected. I knew that It had been in good working condition, so I then attatched two small speakers to the appropriate wires in the harness and re-powered the JVC. It played local FM stations loud and clear, so I assumed that it just won't operate without speakers connected.
I then installed a pair of 4 X 6 Pioneer speakers in the Buick, ran the wires, the power supply and installed an enclosure for the reciever. When I finished the hookup and powered the radio, the same on/off power cycle happened as when no speakers were attached. I checked my connections, and everything is OK, but I can't get the JVC to stay on.
I'm wondering if impedance could be an issue. The Pioneer speakers are 4 ohm while the speakers I tested on the JVC are measuring around 6.5 ohm.