I'm working on a friends '91 740 wagon. He's got no brake lights. All 3 are out, every other light works, and the "bulb out" light on the dash is not on. The fuse is good, there is power to the brake light switch under the dash, and power through it when the pedal is depressed, but there is no power at the back of the car in the wire for the brake lights.

The fuse location tag indicates that the #4 fuse is for the brake light, and "shift lock". Should we be checking for a shift lock switch? I don't see how the two are related, but if somebody says they are I'll take your word for it.

Short of tearing the entire car apart to follow one wire, is there anything I should check? Any thoughts appreciated.

Classic symptoms of a defective bulb out sensor.

Sometimes you can remove the cover on the sensor and see a bad solder joint. The sensor is the big red round one in the relay tray.

Randy

"Classic symptoms of a defective bulb out sensor."

I've been out of town, and just got around to working on this again. You were right....that was the problem. I was at a junkyard and noticed that relay was missing from every Volvo, except one. I grabbed it, they charged me $5, and now I've got brake lights. Best five bucks I've spent in a while.
Thanks

Just a thought. It sounds as if it could be a bad ground. When you checked for voltage at the rear of the car, were you grounding to the chassis or through the lamp ground? I ask as I had a similar issue w/ my 140...finally thought to swap to a new ground point only to have my test light come on finally.
--
When Volvos are outlawed, only outlaws will have Volvos!!