1960 Wonderbar Motor Noise

[Joe M.]

My Wonderbar radio works great when the motor is not running. When the motor is running, the is a loud road coming out of the speaker. I removed the fan belt to take the generator out of the loop and there was no change. I found an old post that indicated the male end of the antenna cable could cause that noise if it is damaged. I don't see any damage at the tip. I tried to find a new antenna cable and struck out. I am out of ideas to diagnose the problem. Any ideas?

[Joe M.]

Re: 1960 Wonderbar Motor Noise

Update: I purchased a generic antenna and cable from O'Reilly's. Plugged the antenna into the radio, started car, turned on radio and the loud noise was the same. Can't hear the radio at all. Ideas?

[Jim L.]

Re: 1960 Wonderbar Motor Noise

Update:. I purchased a generic antenna and cable from O'reilly's. Plugged the antenna into the radio, started car, turned on radio and the loud noise was the same. Can't hear the radio at all. Ideas?

Can you be more specific in describing the noise? Does it vary with engine RPM?

[Joe M.]

Re: 1960 Wonderbar Motor Noise

The noise level increases when I rev up the engine and decreases when I let off accelerator. There is no steady clicking that would indicate spark noise.

[Jim L.]

Re: 1960 Wonderbar Motor Noise

The noise level increases when I rev up the engine and decreases when I let off accelerator. There is no steady clicking that would indicate spark noise.

If the generator isn't running but the noise varies with engine RPM, then spark-related noise is the only possible source.
I assume you've got the ignition shielding in place, yes? And you have, at a minimum, resistor plugs, yes?

[Joe M.]

Re: 1960 Wonderbar Motor Noise

Jim, I have all shielding in place and resistor plugs and wires. The radio stopped working a year ago. The on/off switch had to be replaced. Prior to on/off switch going out, the radio worked just fine with a low level of engine noise. When the emergency brake bulb is blinking, the radio has a faint clicking. That may be a poor ground issue.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

I unplugged the antenna and the noise is still there. I also removed the fan belt again and there was no change in the noise. Maybe the coil condenser is bad.

[Jim L.]

Re: 1960 Wonderbar Motor Noise

Jim, I have all shielding in place and resistor plugs and wires. The radio stopped working a year ago. The on/off switch had to be replaced. Prior to on/off switch going out, the radio worked just fine with a low level of engine noise. When the emergency brake bulb is blinking, the radio has a faint clicking. That may be a poor ground issue.

That's a pretty good clue right there.

If it were mine I'd open up the radio and investigate what was done (or NOT done!) when the switch was replaced. I would do this before looking anywhere else.

Speculation: It's possible there used to be a bypass capacitor wired to the on/off switch which either failed coincidentally at the time of replacement or which was not re-connected when the new switch was installed.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

I will call Todd's Electronics before I open it up. They repaired it and just sent it back. They advertise in Driveline.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

I have completed almost every task I know to do and the motor noise is still there. I removed the ground wire from the valve cover, cleaned out the oil, wiped off everything and re-installed. I crawled under the dash and notice that when I wiggle the ignition wire bundle, it makes the noise increase slightly. Elmer at Todd's Electronics said that he could send me a choke/condenser that I can install inline to the radio hot wire and that might reduce the noise. I have not tested the ignition coil condenser or the wax condenser under the dash.

Any additional member input?

[Jim L.]

Re: 1960 Wonderbar Motor Noise

I have completed almost every task I know to do and the motor noise is still there. I removed the ground wire from the valve cover, cleaned out the oil, wiped off everything and re-installed. I crawled under the dash and notice that when I wiggle the ignition wire bundle, it makes the noise increase slightly. Elmer at Todd's Electronics said that he could send me a choke/condenser that I can install inline to the radio hot wire and that might reduce the noise. I have not tested the ignition coil condenser or the wax condenser under the dash.

Any additional member input?

Know that a choke and a condenser are NOT the same thing. A choke is installed in SERIES with the power connection while a condenser is installed in PARALLEL with the power connection.

[Keith K.]

Re: 1960 Wonderbar Motor Noise

Ignition noise is a challenge in Corvettes as the fiberglass body doesn't provide any shielding for the radio. The antenna is in the rear to be as far away as possible from the source of the noise (engine). The problem is probably not in the radio. Since you have all shielding in place and resistor plugs and wires, it is likely a capacitor or ground. The antenna mounting in the rear has a ground strap from the base of the antenna to the frame - check that. Then there are four noise suppression capacitors any one of which could be bad. One goes from the positive side of the ignition coil to a grounded bracket, another is mounted to the voltage regulator, another to the generator, and another under the dash. There are other ground straps under the vehicle which are for radio noise suppression, but they are minor compared to the items above.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

Thanks for the explanation. Maybe the repairman said he could send a choke or a condenser. I really don't understand what is going on.

[Joe M.]

Re: 1960 Wonderbar Motor Noise

The only items I have not check are the capacitors/condensers to see if they are good. I reviewed several Youtube videos on how to test a condenser with a multimeter, but I could not get results that I was confident in. Maybe I need a meter that provides a read out in microFarads. If the meter reads out 0.5 MF, does that mean it is good?

[Keith K.]

Re: 1960 Wonderbar Motor Noise

In a car radio, the choke is usually built into the radio and since you had the radio rebuilt that was probably checked and replaced if bad. A condenser is the same as a capacitor. If the repairman sends you a known good capacitor (condenser), you could try replacing each of the 4 capacitors listed above. You mentioned using a generic O'Reilly's antenna - this could be the problem. A generic antenna assumes that it is mounted to a steel body car which is grounded by the base of the antenna attaching to the steel body. A Corvette body does not ground the base of the antenna. You would need to attach a ground wire from the base of the antenna to the steel frame of the Corvette.