Designed For Failure

by Dick Zakrzewski

There is a design flaw in imported after market '41-48 Chevy taillight assemblies that will cause an intermittent operation or a failure to operate. The problem occurs because bulbs in the lock position are 60 degrees out of phase with the socket contacts! See Sketch #1. A properly designed socket will place the bulb contacts directly over the socket contacts.

The shaded area in Sketch #1 shows the maximum amount of "potential" contact in the flawed light sockets for 1157 bulbs. In reality the contact area is much less because the bulb contacts are hemispherical in shape. The shaded area is further reduced when "bright" bulbs are used, because the contacts are 1/32 smaller in diameter. See Photo #1 and Sketch #2

Photo #1

Photo #2

I first detected the problem during an attempted test of "bright" bulbs in my coupe. The 1157 bulbs worked, but the "bright" bulbs wouldn't.

If you have these flawed taillight assemblies, you may replace the socket with a LS6243 double contact ¾ inch socket. See Photo #2.

Note:It is quite possible this manufacture produces taillight assemblies for other model cars so if you have a similar problem, check the sockets.

Steps to replace defective socket:

• Cut the defective socket from the taillight assembly with a hack saw as close as possible to the swaged portion of the socket. Use a very fine blade.
• Enlarge the I.D. of the socket hole with a round file or die grinder until the two halves of the swaged portion of the socket are separated. See Photo #3.
• Discard the outer ring and push the new socket into position. Note the hole is a little larger than ¾ inch will require use of the inner swage ring to retain the new socket. See Photo #4
• Tap down the retaining tabs of the socket to tighten fit. Position the taillight assembly in a vice with the socket side down and the swaged portion of the socket resting on the jaws of the vice when taping down the tabs. Do not tighten the vice on the socket.

Photo #3

Photo #4

Dick Z