hummmmm....hmmmmmm

[jerry]

with the motor off if i turn on the lights on my 55 which still sports its original 6v system i hear a hum.  is this normal?  what is causing the hum?  everything seems a-okay otherwise.
in the dark,
jerry

[wm link]

Cadillac had been 12 volt since 1953. I suspect that you have that eyeball (Autronic eye) on the very left side of your dashboard. The amp makes a hum from the left fender well under the hood. press down once on the floor dimmer switch and that should turn it off.

[Don Boshara #594]

Could it be the Autronic Eye headlite dimmer?

[Doug Houston]

The other guys surely have the right answer. On the early Autronic Eye systems, the big box in the engine compartment has a vibrator power supply in it, similar to that in the radios of those days. The dash unit has a photomultiplier tube in it, laying sideways in the wide part of the head. It needs several hundred volts to operate, and there is a tube in the amplifier box that operates on  high voltage. Normally, its very hard to hear.

My recollection of those systems is that there is a switch on the dash....usually on the light switch module that can turn on or off the dimmer. With the eye turned off, you just go back to normal dimmer switch operation. I have the Guide Lamp service sheets on them, I should look it up.