I have a 1992 T&C. Sometime in the past few days, I started getting an electrical hum in my speakers. I didn't think much of it, until I started also getting "static" shocked when leaving the vehicle. Anything electrical (winshield wipers, door locks, etc) that cause a sudden change in electricity use are audible on the radio.

This happens while using a tape, so it is not FM interference.

I did a little bit of troubleshooting, pulling all of the fuses one by one to see if any would make it stop. None did. I thought it was a general engine elctrical noise, but I found this:
If I put the key in accessory mode (for listening to the radio with the vehicle off) there is no electrical noise. However, if I turn the key to just before starting the engine, the noise shows up, without actually having the engine started.

Therefore, the problem is with something that isn't on with the key in the accessory position but is on when the key is in normal driving position, without the engine running. The noise seems to be cyclical, with a steady, high-ish pitched hum, and a very slight click about every second or so. I have narrowed out things like the lights, door locks, windows, the radio itself, and the dash.

What electrical systems are activated between these two instances, so I can narrow down what else to examine? Thanks.

 

add another ground strap to your radio facory?? or aftermarket U have a bad ground on your radio. Clean it off if u can find where it goes into the body or just add another one

 

It is a factory radio. I will try reseating the ground strap. However, as I mentioned, the vehicle is now zapping me every time I get out of it, which has never happened up until this point.

 

This may be completely wrong... but I know there are resistors in spark plug wires that prevent EFI from interfering with radio signals.(It would sound like a buzz in your speakers.) Sometimes these resistors can burn out, but you still get current through. When was the last time you replaced your spark plug wires.... It may be time for a tune up anyway?

 

I still think he needs to check the condition of his electrical grounds, both at the radio to body, body to engine and engine to battery.

Radio interference is addressed by both the spark plug and the plug wires - some of the plugs have resistors built into them, usually used on cars with 15kV and 20kV ignition systems (most of the old point type systems). Newer cars have cables made of carbon fiber and are designed for a resistance of 3kOhm/ft - 5kOhm/ft. to act as an electrical choke and eliminate the electrical interference. If plugs and wires outside factory specs or equivilent are used, then some radio interference can occur.