1984 - 1996 Corvette: Service Bulletin: Windshield Wipers Chatter and/or Wipe Unevenly

This service bulletin came out in April of 1987 but applies to all 1984 - 1996 Corvettes and is a valuable source of information on the care and service of your C4 Corvette’s windshield wiper system.

Subject:   Windshield Wipers Chatter and/or Wipe Unevenly
Model and Year:   Domestically Produced Passenger Cars
Source:  Chevrolet Dealer Service Bulletin
Bulletin No:   87-104
Section:   8E
Date:    April, 1987

TO:  ALL CHEVROLET DEALERS

Some vehicles may exhibit a condition where the windshield wipers chatter and/or wipe unevenly.  Several items may contribute to this condition.  To completely repair this condition, all applicable items covered in this bulletin should be checked and repaired as necessary.

Clean Windshield Glass

Clean windshield glass with GM glass cleaner, Bon Ami (Trademark), or equivalent.  The cleaner used should be one which will not harm paint finish or scratch glass.  The glass is cleaned when water no longer "beads up", but "sheets" across the entire glass surface.

Clean Wiper Blade Elements

Remove wiper blade assembly from wiper blade arms.  Clean Rubber elements with a cloth which has been saturated in a solution of 50% water and 50% GM Opti Kleen, or a solution of 50% water and 50% methyl alcohol.  Rinse blade assemblies with water and reinstall on wiper arms.

Check Fit of Windshield Reveal Molding (Figure 1)

On vehicles equipped with depressed park (hidden) wiper blades and windshield lower reveal molding, check the fit of the reveal molding across the base of the windshield.  The lower reveal molding must fit uniformly along the glass surface to allow the wiper blades to move freely from the glass wiper area to the park position when the wipers are turned off.  Gaps in excess of 1.0mm (.040 in.) should be corrected using the following procedure.

1. Remove both wiper arm assemblies.
2. Remove self drilling screws which retain the reveal molding.
3. Clean the underside of the lower reveal molding and the windshield glass.  Remove any obstructions which prevent eh reveal molding from matching the glass contour.
4. If necessary, the lower reveal molding should be reformed as required to improve the fit.  Care should be used to prevent marring the molding surface.
5. Reinstall the lower reveal molding using new self-sealing screws (P/N 20564495) starting with the center screw and work outward.  Use over sized screws if necessary.

Check Windshield Wiper Arm Pressure   (Figure 2)

1. Turn on ignition switch and wipers.  When the right hand wiper is in the middle of a wipe stroke,, stop the wiper system by turning off the ignition switch.  Proceed with the following steps to measure the right hand arm pressure.  prior to measuring the left hand arm pressure be sure the left hand arm is in the middle of the wipe stroke.
2. Remove the wiper blade assembly from the wiper arm.
3. Attach a scale to the wiper arm attaching pin and measure the force required to lift the wiper arm perpendicular to the windshield to the normal working height (i.e., the height of the blade attached).
4. if the force required is not within the specifications given below, the wiper arm assembly should be replaced.

Check Wiper Blade Mounting Angle   (Figure 3)

With the right hand wiper arm assembly in the middle of a wipestroke and the wiper blade assemblies removed, visually check that the blade assembly mounting pin on each wiper arm is parallel to the windshield.  Replace the wiper arm if necessary.

Check For Blade Set   (Figure 4)

Remove the wiper blade assemblies from the wiper arms being careful to note orientation for reassembly.  Look down the length of the blade element.  The rubber element which contacts the glass must be on the center line of the blade assembly +/- 15 degrees.  Replace the element if necessary.

Check Wiper Arm & Park Position Adjustments   (Figure 5 & 6)

When the wipers are shut off after operation on wet glass, both wiper arm and blade assembly should be fully seated on the park ramps.  In the full left stroke position, the tip of the blade element must be no more than 78mm (3 1/16 inches) from the pillar.  if wipers require adjustment, refer to section 8E of the appropriate Service Manual.

Chevrolet Motor Division
General Motors Corporation