The Volvo Parts, Accessories &
Performance Specialists Since 1963

Bulb Integrity Sensor Location & Diagnosis

2011-03-09 - IPD Staff

The two common locations for the bulb integrity sensor are:

1. Under the drivers side dash (200)
2. Behind the ashtray/fuse box (700/900)

The bulb integrity sensor is cylindrical in shape and is colored red. Diagnosis for the circuit should start with the brake switch.Using a test light check for power at the brake switch connector. The light should illuminate on both wires when the brake pedal is depressed. If power is not present, check the fuse and replace as necessary. If the problem persists, proceed to the rear of the vehicle and check the taillight circuit boards.These boards are known to wear over time especially on the circuit traces where they contact the connector and/or the bulb sockets.

The next step is to check the individual sockets and bulbs for corrosion or wear. Be sure that bulbs are in good shape and are the same wattage and from the same manufacturer. Check the sockets for damage and wear on the inset contact points and also on the splayed out contact points. Inspect the corresponding contact area on the taillight circuit boards. Finally remove the bulb integrity sensor and locate the incoming power wire from the brake switch, consult your service manual to identify the correct terminal position for your model. Once incoming power has been verified, the remaining link in the circuit is the integrity sensor. Skilled individuals may fashion a bridge to jump power from the incoming terminal (from the brake switch)and bridge it to the outgoing terminal (to the brake light) to verify sensor failure.