92 C2 warning lights Christmas tree effect

[jim fling]

I had the alternator replaced last year and after that the radio started have a "sparkplug" like noise after the car had been driven about 40 minutes. The noise changes with engine speed and it is there even when the radio volume is all the way down. Some times, especialy when there is a larger electrical load (lights and other things on) the warning lights all start to cycle and the warning horn comes on. I turn off the key momentarily and it acts like a reboot and everything goes back to normal except the radio noise. Sometimes it happens several times then the lights stay off the rest of the day or night. The technician said that one of the sparkplug wires from the lowerr distribritor was bad. I unpluged the coil wires one by one to each distribritor and the nois was still there. The alternator voltage is correct and never below 14 volts. The ripple on the DC is OK but there are high voltage spikes on the voltage when the noise is present. Spikes of about 20 volts. I think the new alternator has a leaky diode but the dealer will not change it again.
Any ideas?