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The dash bulb-out indicator had been out on our '92 244 since we bought it a year ago. All the lights were working, so I spend my time on more immediate concerns. The indicator came on in position 1 (parking lights). The only clue to the problem was that one front parking light was slightly brighter than the other. I assumed that an incorrect bulb or an out-of-spec bulb was causing an impedance mismatch that triggered the bulb-out relay.
This weekend I took off the turn signal lenses and inspected the parking light bulbs. They were the correct type, and identical down to the manufacturer. However, the driver's side bulb was undoubtedly brighter than the passenger side bulb. Hummmm...
Looking closely, I saw that these were two-filament bulbs, and that one of the two filaments was larger than the other. I also noticed that the "big" filament was lit on one light, and the small filament was lit on the other, accounting for the difference in brightness, the impedance mismatch, and ultimately, the bulb-out warning indicator. The question was, why was current going to different filaments?
I removed a bulb from the passenger side parking light socket, and noticed that the bulbs' base have offset locating pins so they can into "screw" (10-15 deg rotation) into the socket in only one direction. The bulb bottom had two terminals, one for each filament, but the socket had only one terminal, which was mounted to a spring-loaded plastic disk. It seemed that the socket terminal disk was rotated 180 deg from where it should be. This disk has small tabs that fit into grooves in the socket to prevent it from rotating. There was no sign of mechanical damage, corrosion, etc.
I decided to rotate that white terminal disk one way or the other. I pushed the green wire going into the socket into the socket, which in turned forced the terminal disk forward until its locating tabs cleared the grooves. I then rotated it 180 deg and pushed it back down into the socket. I reinstalled the bulb and turned on the lights. The parking lights on both sides had the same intensity, and the bulb-out indicator was off.
In the grand scheme of all things Volvo, this was a minor problem. A PO or some mechanic probably accidentally rotated the terminal disk when changing a bulb. However, it was an interesting little exercise in troubleshooting.
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'88 244GL, '89 244GL, '90 244DL, '91 244, '92 244
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