Hi all,

Last week the low beam headlights would not come on after installing an aftermarket radio in my wife's 1991 740 wagon with B230FT engine. I only dealt with the radio installation wires, so I'm not sure what could have happened.

Here are the symptoms. All functions of the car were working prior to the installation of the radio. Now, the low beam headlights will not come on with the headlight switch in the on position and the ignition in KPII. The parking lights do function with the headlight switch in the parking light position and the ignition in KPII, and if you were to pull on the high/low beam switch in this position, the high beam headlights will come on as long as you hold the switch in the activated position.

Here's what I have done, the FAQ stated to pull the Bulb Failure Relay out and check for voltage in the 56b terminal first, if voltage was there but not found at the low beam fuses, the relay would be bad. Unfortunately, there is no voltage at terminal 56b, and upon interior inspection of the Bulb Failure Relay, there was no visible damage or burned traces. Now I am looking for where the power originates that would supply terminal 56b. All fuses in the CEU check out ok, and I have power in all slots that should have it. I do not have a schematic for the Central Electrical Unit, and do not have any indication of where else to look. All suggestions are appreciated, thanks for reading.