I believe the infamous "bulb out" sensor only monitors the low beams; as mentioned by others, you'll lose the functionality when you put in relays. That said, you won't miss it - you'll notice when one of the 80W low beams burns out!

What you'll end up doing is to add an additional wiring harness, fuses & relays, using the existing headlight wiring to power the relay coils via terminal #85 on the relays.

I've done this conversion on my 740; most folks use separate matching relays for each side of the low beams, to keep the sensor happy. I used a single relay for low beams and connected both sides of the OEM headlight wiring to the #85 terminal, with a diode in line on each side between the wiring & relay terminal. This isolated each side from the other, yet balanced the current fed to the relay from each side of the OEM wiring thus keeping the "bulb out" sensor happy & the warning light off. The voltage drop across the diodes (about 1 volt) hasn't affected the operation; the relay coil seems just as happy at 12.8 volts as at 13.8 volts.

I've also wired the H1 bulbs as separate driving lights & used a Volvo OEM driving lamp switch (they call it a "spot light" switch).

Don't just rely on crimping the wire terminals - solder them as well! You're going to be drawing a LOT of current to power the bulbs, and you want the best connections you can get.

For best instructions & generic wiring diagrams, check out Dan Stern's automotive lighting website.

I am almost certain that the headlights have no effect on the bulb failure system. I believe it monitors all external lights except : rear fog light,

headlights, back-up lamps.

Steve

Your goal is sort of an oxymoron. The purpose of adding a relay to operate the filaments is to move the loaded circuit to one that is more capable, which means removing most of it (except the relay coils) from the original headlight wiring. The only problem with that is, the lamp out sensor works by comparing the current draw of the L cicuit to that of the R circuit, meaning the current has to flow THROUGH the sensor and original wiring.

You can easily add relays and keep the light off by moving the Volvo wire going to each headlight filament to the coil (#85) terminal of a common Bosch relay and ground the other side of the coil (#86). Connect the N.O. contact (#87) of each relay to the battery through individual fuses (or tied together and fed by a common fuse). Now connect the #30 terminal of each relay to the filament whose wire is on its #85 terminal. Example; If the factory left low beam wire is connected to the #85 of relay "A", then #30 terminal of that relay goes to the filament of the left low beam lamp.

Your bulb out system will continue to monitor the car's other lamps, but will no longer be able to detect a failed headlamp.

Prewired connectors are available for these 5 terminal "cube" relays to make the job easier.