Volvo 740 Brake Light Problems

Current is reaching the rear light assemblies when the headlight switch is off from the brake light switch via the bulb integreity relay and a ground is being provided through the parking light filament in the bulbs. When the light switch is on there is no ground available hence the bulbs don't illuminate. The problem is either a bad ground at the circuit boards on the tail light assemblies or you have the wrong bulbs somehow installed in the sockets. The right hand bulb holder (passenger side US) should be white, the left side should be black, and both should have an 1157 bulb (twin filament) installed.

Use scotch brite to clean the contact strips on the circuit board, clean the bulb contacts and bulb holders. Remove the edge connector and lightly clean the contact lines on the edge card surface. Use pliers to squeeze the contacts in the connector to provide slightly more tension on th edge card when installed. Just work your way along the connector with the pliers, don't remove the contacts from ther respective cavities. If the circuit board is still serviceable and the black ground wire from the crcuit board to a grounding screw just outside the opening for the light assemsbly is tight and clean the brake lights should work as designed.

Bob

My wife's '89 740 GL has lost both its main brake lights. The light over the trunk (back window) still works. Bulbs are good, contacts clean. No voltage at the rear connectors when the brake pedal is pressed & the back glass light is lit.

The owner's manual says that fuse #4 powers the brake lights, & pulling it kills the back glass light.

Other posts talk about 'integrity relays' & repair of same. Could this be my problem, & if so, where are they on the 740? I've followed the bundle from the left tail light assy up to the seat back without finding any connectors.

Thanks,

Charlie