940 1993 Stop lights do not work

rocky334 · Post by **rocky334** » 23 Nov 2009, 08:04

All other running lights including headlights, parking lights, tail lights, turn signals and backup lights work OK but the stop lights do not work when the brakes are applied.

Fuse No. 4 which provides power is good and the brake light switch that
is operated by the brake pedal itself is OK. Since neither light works I suspect that the problem is ahead of the bulbs themselves.

Any suggestions or help will be much appreciated. Thanks, Rocky

Post by **billofdurham** » 23 Nov 2009, 12:36

This failure is often caused by a faulty bulb failure warning relay - the round one, back row left on the relay board.

Is the third brake light working?

Bill.

rocky334 · Post by **rocky334** » 03 Dec 2009, 01:07

billofdurham, I followed your advice and "zingo!" it worked perfectly. The Bulb Fault Relay was in fact the culprit, after removing the plastic
cover on the cigarette lighter and the two underneath phillips screws & the small compartment just above the ashtray I had perfect access to the relay panel.

Quotes for a new relay averaged about $130 so I decided to open up the relay and found several questionable solder joints which I reflowed with small tipped soldering iron, the cylindrical relay cover easily slipped off and back on.

The big bonus of the entire project was that the total cost to me was
"zero" $$$$$$ and even further, the cruise control now also works
perfectly.

This forum is proving to be a priceless resource for a "shadetree" mechanic like me, again, Bill thank you so much. Rocky334

sli

Post by **billofdurham** » 03 Dec 2009, 12:29

You are welcome.

Thank you for the update which will help others with the same problem.

Bill.