1968 Corvette: Service Bulletin: Whine Noise in Radio

Subject:   Whine Noise in Radio
Model and Year:   All 1968 Vehicles
Source:  Chevrolet Dealer Service Technical Bulletin
Bulletin No:   68-T-11
Section:   XII
Date:    January 2, 1968

TO:  ALL CHEVROLET DEALERS

On some 1968 vehicles, reports or noise, described as Delcotron whine emanating from the radio speaker, have been received.  This noise is most pronounced when the Delcotron charge rate is high and will vary in intensity when the volume control is adjusted.

An in-line filter designed to suppress Delcotron whine in radio speakers is now available through United Delco Distributors.

The filter should only be used after the following checks have been made to locate the source as being the Delcotron.

1. Start and run the engine using all accessories (lights, heater, wipers, etc.) and listen for noise.  Operate volume control to determine if noise will vary.
2. Disconnect the field connector (2 wire connector) from the back of Delcotron and again listen for the noise as in Step 1.
   
   
   1. If noise is not completely eliminated - Do Not add filter coil. Inspect radio per Bulletin TSB 66-7 "Radio Trouble Diagnosis", dated 7-28-66.
   2. If noise is completely eliminated - install filter coil per Step 3 below and re-evaluate as in Step 1.
3. Install Filter Coil Assembly Part No. 1222834 in series with the three lead connector on the back of the radio. Tape the filter to the instrument panel wiring harness for support.

Note:  Filter Coil Assembly is available through Delco Distributors only.

Chevrolet Motor Disivion
General Motors Corporation