Low beams not working
 

Long story short, my low beams just stopped working, high beams still work, but no lows. I've checked fuses and all that jazz and need just a little more help on where to go with this. Just looking for someone to point me in the right direction, or maybe someone who's had the same or a similar experience.

The car is a 91 s5, N/A, all stock. Thanks in advance for the help.

Probably the switch or it's subharness.
Or both.

There are only three wires that go to the headlight bulb, negative ground, positive low beam, and positive high beam. To eliminate the obvious, put an ohm meter the one of the bulbs and check for continuity between negative/low and negative/high. If you have continuity, and the highs go on and off with the high beam switch, then you simply have no positive getting to the low beams.

So the obvious is power is interrupted somewhere between the battery and the headlight bulb. So congratulations, you get the arduous task of finding where the open circuit is. It could be a disconnected connector, bad switch/relay, or even a broken wire. Before you ask, there are not separate fuses for low beam and high beam.

Open your FSM, or online FSM you can access via the sticky, find the headlight diagram to use as reference. Starting from the ignition switch where you should for sure see power, start checking for power between each point where a connection is indicated in the FSM. Any connection. You might find it in 10 minutes, it might take a number or hours before you narrow it down. Except for maybe starting from the middle of the circuit and working backwards, there is no shortcuts so don't ask.

Have fun.

PS For what it's worth, I once inherited a car that had low beams but not high. It turned out that the high beams in both bulbs were blown. Thus why I suggested you check the bulbs first.

PSS The headlight relay is one of the bank of underhood relays lined up between the radiator and front bumper.

Each bulb receives three wires. Besides the ground wire, the other two wires come from the Dimmer Relay. One wire is Red/White while the other is Red/Black. R/B is low beam and the high beams are R/W. If the Dimmer Relay was working properly, then w/the low beams on, the Red/Black wire coming from the relay and running to each headlight would have voltage to it.

Here's what you check.

1. Bulbs
2. Fuses
3. Relays up front
4. Switch inside

If none of that, do what I did and install a Painless H4 headlight conversion harness. Couple hundred dollars, but you won't have to worry about melted harnesses or anything from new high current bulbs in old wiring.

Painless and a couple hundred dollars to do not go hand in hand.

So I'm back under the car and I just noticed that the fuse panel reads 30a for the headlights, but there's a 40a fuse in it's place. I've never noticed that before.