'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.

 

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.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

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.

 

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