This is where the $35.00Volvo wiring diagrams book and a $5.00 VOM pays for itself. First double check the low beam filaments on the 9004 lamps or buy a new one to check. Tracing the circuit, I would first give an equal look at the red bulb malfunction relay and the head light relay which should be marked with a K in the front row of relays. After that, the head light switch, the lever switch on the steering column, and the ignition switch.