That's pretty much what I ended up doing on Sunday. Only I replaced all turn signal bulbs and cleaned the right front ground having previously cleaned the right taillight ground on a different matter.

If I had to bet, I'd say the ground was the problem. It was kind of cruddy whereas the bulbs all looked pretty good. But who can tell? I should have been methodical and seen if cleaning the ground alone would remedy the situation.

While I was at it I replaced all four taillight bulbs, one of which was rather dingy. That cured an intermittent BFW display (the aforementioned different matter) which occured when first turning on the lights but would always cease on it's own within a matter of seconds. Oddly, flashing the high beams would also make it stop.

All of this in anticipation of a safety inspection.

Thanks to all who replied.


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'80 DL 2 door, '89 DL Wagon

First remove bulbs and check for/remove corrosion on the bulb contacts and the inner surface of the holders. No joy? Install new bulbs.

The TS relay senses a current draw lower than what should be seen with two good bulbs, to trigger the double-speed flashing. As you suspected, that is its bulb failure indicator. Reduced current flow through two bulbs will give the same result.
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Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), 98 S90 (recently sold) and 2010 XC60. Also '77 MGB and four old motorcycles