My 1994 940 Sedan randomly (25% of the time) indicates bulb failure (instrument panel lamp) for turn signals, back-up and brake lamps, although none of these lamps are actually out. Any ideas as to why? Thanks!

Have had same ongoing problem with lights on both of my 95 940s, as well as previously owned 240s. FULLY agree with other posts. I periodically remove rear lamps, thoroughly clean bulbs and sockets. I regularly observe the single small lead/tin contact at the bottom of the lamps is too soft and becomes deformed by the tension of the spring steel contact located within the socket. The lead/tin 'tit' develops a concave groove in it, which leads to sporadic connection imbalances (higher resistance causes less amperage), and the bulb failure lamp illuminates.

Presently, my left blinker (never the right blinker) flashes at twice the regular speed. Occasionally it will blink normally, but will remain unpredicatable until I clean and/or change the bulbs?????

HOpe this helps.

The bulb out sensor is not for back ups or turn signals. It's for low beam head lamps, brakes and rear running lights only. Have you checked them when the dash light is actually lit. Does it come on only with running lights on or only with headlights on or with brakes applied?
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David Hunter

I'll second Bruce's diagnosis. You may have a loose bulb, a bulb with a loose filament, dirty contacts in a socket, or a loose ground in one of the lamp circuits. Be sure the two bulbs in each circuit are the same manufacturer and number. I've also had bulbs which were enough out of balance when cold to turn on the bulb failure light. After a few seconds of being on, the current draw of the two bulbs seemed to equalize and the bulb failure indicator would go out. This shouldn't be too hard to find.

Bruce & Jim - Thanks very much for your responses to my question about the bulb failure lamp. I'll make sure the bulbs are the same on both sides and that the sockets are corrosion-free. My only remaining question is why does the failure lamp flash on-off in turn-indicator-relay rhythm if the sensor doesn't monitor that circuit? Thanks again!

John Sloss

You did not originally say that ir was in unison with the turn signal. Both sides or just on one side?

You may have a bad ground at the rear. The rear lights on each side have a ground shared by brake, tail and turn lights. If the ground is bad and then has to carry the extra current for the turn signal bulb that would set up an imbalance for the brake and or tail light circuits which would trigger the bulb out sensor.
David Hunter

David - I have ensured that all front and rear bulbs are working while the bulb failure lamp is indicating a problem. The problem occurs maybe 25% of the time when I use the LEFT turn signal or apply the brakes - with or without the headlights on. I haven't tested it with only the running lights on. How would I check the ground? I have a multi-meter, if that helps. Thanks!

John Sloss

Inspect the ground wiring behind the light in the trunk. If you really want to use the meter look for the voltage to rise from OV somewhere on the ground path from each bulb to its final connection to chassis ground. A physical inspection should yield a clue though, look for looseness or corrosion.

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David Hunter

I don't recall if you have a sedan or a wagon. I just took a look at my '93 940 wagon. The rear lights have a ground on each side. There is a black wire which has a female connector on it an this connector slides onto a metal tab on a bare metal strip which is obviously connected to the chassis. A sedan should be similar.

The headlights and other front lights have ground wires running to a connection on the inner fender just in back of the headlights, as I remember.

The sensor does not test the turn signals or back-up lamps. Just headlight Low Beams, tail lights and brake lights.

The sensor may be seeing a current imbalance between Left and Right side brake lights, due to corrosion in a bulb socket or circuit connector
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Like a previous poster stated, you should have matching bulbs. If the bases of the bulbs are made of different color(ie)silver base, gold base it could trigger the lamp. Got this bit of info from a Volvo tech.

Good Luck.

95' 964 164k