I need brake light troubleshooting tips for 1993 940 Volvo turbo

You mean day running lights?could unhook .

You damaged a module .

bulb failure warning relay has failed.behind your front ashtray last relay on the left .round one change it try on ebay.

2012 Volvo S60

Hi em1cl, I suggest you check fuse #D3, 15A in the fuse block located in the trunk.

this means the brakes are low, have your brakes checked, hope this helps.

Sometimes the fuse looks good,but replace it anyway,that sensor in under your dash,its red and round.

brake fluid low, or brake pads need replacing.

Is there a switch on the left side of the dash that has a red lens and a wavy line across it? If so, you have a rear fog light switch and it has been activated, causing your brake lights to come on each time you turn your headlights on. Flip the switch and the rear lights should display only the parking lights with the headlights on.

behind fuse panel big red round relay and you can normally solder bad connection inside if you look close