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'86 740 sedan front turn signals and corner markers

so I just had an intermittantly dying front turn signal.. probably intermitant socket contacts since the bulb doesn't look blown.

The generic replacement part number from the kragen book is the sylvania 7528, but that bulb is clear, and the lense cover for the turn signal (below the main headlights right?) is also clear.

Obviously a white lense and white bulbs does not make for an orange turn signal (which I thought was a requirement). So it looks like the Kragen reference is wrong and I really need the sylvania 1157A which I verified by calling a sacramento volvo dealer.

Using the 1157 Amber bulb, I noticed it's a double filament bulb but only one filament is powered. Do I have an electrical problem? something going on with contact or wiring or is this really the way it was designed? with a double filament and only powering one? Sure seams weird.. any reason why volvo would have done that?

-Ethan

also just to be sure... The amber corner lenses are the markers that are on with the parking lights or full lights, right? I wasn't sure if I had my sockets switched.. thought the corner would more logically be the turn signal.

Reply to
Ethan
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You are correct in your logic that the right bulb is the 1157A, and your lights are working as designed. Back in the old days (1980s!), the only bulb was available amber was the 1157. So, Volvos of that vintage, which had separate bulbs for corner/sidelight and signal had dual filament bulbs but only used one filament. Because the corner used the low power filament and the signal the high power filament, if one of the bulbs blew, you could just swap the bulbs between the 2 lights.

Reply to
Mike F

Always did wonder why they did that, but as you say, all Volvos from the '81

240 series until newer than any I've owned used the dual filament amber bulbs but only used one filament.
Reply to
James Sweet

I think it was some bizarre US lighting regulation dating back to the sixties. Amber lenses were the only acceptable method for causing amber light. The standard 32watt bulb for turn signals was an 1156. Since clear lensed cars could be illegally converted 1156A bulbs were never manufactured. Volvo found that they could use an 1157 socket in all applications world wide and have country specific corner lighting and accomodate each application by changing the bulb to amber or clear, one live contact or two, as the regulations warranted.

Bob

Reply to
Robert Dietz

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