Sorry

Maybe the brake light switch is failing. (it is actuated by pressure of the brake fluid.)

I haven't seen a pressure activated brake switch since my '56 CJ-5, all my Volvos have a switch at the top of the brake pedal that closes when the brakes are applied. The '86 740 that I had was the same way. Dave Shannon snipped-for-privacy@cox.net (Spring Valley CA)

1988 240 DL 18X,XXX 1985 240 Ti 20X,XXX 1984 245 DL 20X,XXX 1984 245T 19X,XXX '01 Jeep Wrangler Sahara 10K

My '66 122s had a pressure activated brake light switch, but all Volvos since then have had a switch activated by pedal movement.

To the original poster, the brake light circuit consists of battery - ignition switch - fuse - brake light switch - bulb failure sensor (where the wires split to 2 or 3 depending on the number of brake lights) - brake light bulbs - ground.

The brake light switch is on the pedal, it should have power on one wire with the ignition switched on, and at both wires when the brake pedal is depressed.

The bulb failure relay should have brake light power coming in on the wire from the switch when the pedal is depressed, (terminal marked 54) and power out on the terminals marked 54R and 54L (and a third one to the window brake light, if equipped).