My '78 Delta suddenly has no lowbeams ..
The Parking lights come on, and the High Beams will switch on/off, but regular headlights are off / not working ..
I had my son crawl under the dash to look for a fuse & check owners manual, but apparently there is no fuse for those, it's supposedly a breaker built into the light switch ( correct?)..
I had a brand new unopened bulb, & swapped it with 1 of the non functioning lights, no difference.
Any suggestions?? Thanks

 

Yeah. Start by looking at a wiring diagram, which shows you that 1) there is no fuse, and 2) the high beam and low beam circuits use the same wire out of the headlight switch, so if high works, the switch and power to it is NOT the problem. Continue to trace that wiring, and you'll find that the dimmer switch is the most likely failure point, and the terminal for the low beam wire in the firewall connector is the second most likely cause. The high and low beam bulbs share a common ground, so if all four high beams come on, the grounds are good.

Disconnect the wires from the dimmer switch and jumper the yellow power wire to the tan low beam wire in the connector. Now turn on the headlight switch and see if the low beams come on. If they do, replace the dimmer switch. If not, find the break in the tan wire from the switch to the headlights.