Both low beam headlamps quit working suddenly. High beams still working. Fuses look good, plus, low beam driver and low beam passenger are two separate fuses. Is there a hidden low-beam relay?

PAWEL IS A BOT. HE POSTS GENERIC ANSWERS. AND OVERLAYS NAME OF YOUR CAR. 82 GENRIC ANSWERS HIM
AND LIES ABOUT IGN SWITCH.
NOW YOUR CAR.! FACTS, ONLY, 1 CAR
LEARN TO USE THE DMM , CORRECTLY;
HEAD LAMPS ON.(SWITCH) NO KEY IS NEEDED FOR HL.
IS DRIVER LEFT OR RIGHT,? IN USA LEFT.
IS HIGH AND LOW BEAMS DEAD LEFT? No TOLD AT ALL.
PUT METER BLACK LEAD TO THE BATTERY NEG LUG
THEN PROBE RED TO ALL WIRES OF DEAD LAMP 1 BY 1.
12VDC IS GOOD 0 BAD
IF LAMP GROUND PIN READS 12VDC <<< GROUND FAILS.

LEFT LAMP USES GROUND LUG G101. IF R

CAR HAS DRL. SO DRL AND MANUAL LAMPS FAIL
HIGH , LOW , AND FLASH HIGH>? NOT TOLD
DOES ENGINE RUN? OMG NOT TOLD.
THIS CAR RUN HL RELAYS BY BCM CONTROLLER BRAIN


FUSE ARE ON THE OUTPUT OF ALL HL RELAYS
SO IF ALL FUSES INPUT(TOP) ARE DEAD,THAT MEANS
BCM IS FAILING. OR THE SWITCH TO IT.
OR FUSES BLOW TO BCM
WE SCAN THE PCM/BCM TO SE WHY.


HEAD LAMPS ON THE 4 FUSES ALL 4 RIGHT SIDE ARE
12VDC, IF NOT BCM IS MESSED UP, OR RELAY DEAD.
HE LOW BEAM RELAY RUNS BOTH SIDE
SAME WITH BEAM. A RELAY FOR IT.
DRL HOT ONLY IN DRL MODE.
DRL; HAS A SUN SENSOR (AUTO MODE)


BOTTOM HERE IS HEAD LAMPS.SIDE.

HEAD LAMPS ON USA WORK EVEN KEYOFF
SO DOES BCM TO DO THAT, MAIN BATTERY NOT DEAD

Did you test the low beam electrical circuit using a volt meter ? Look at a wiring diagram to see what all is involved in turning the lights on ? Do you know how to test electrical circuits ?
Also reading service repair manual about the head lamps opp. would be a good thing to do .
Headlamps
The major common components of this system are the body control module (BCM), ambient light sensor, multifunction switch, park brake switch, and the headlamps.
The headlamps may be turned on in 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, normal operation occurs. Second, with the headlamp switch is placed in the AUTO position, automatic lamp control (ALC) occurs. During ALC control, the headlamps will be in daytime running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions.
The low beam relay and high beam relay receive battery positive voltage directly from the battery through the HDM and COILS fuses in the underhood fuse block. The BCM supplies a ground signal to the low beam relay coil for automatic headlamp control and normal headlamp operation. The BCM also supplies ground to the high beam relay coil for high beam headlamp operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the low beam relay energizes sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. The dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-Pass (FTP) position from G102 to deactivate the low beam headlights and activate the high beam headlights. With the headlights in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.

Low Beams - Standard
The standard low beam headlamps receive voltage from the headlamp driver module located in the underhood fuse block. The body control module (BCM) controls the headlamp driver module with the headlamp low beam relay control circuit. Low beam control is determined by a signal on the headlamp dimmer switch signal circuit from the multifunction switch. When the headlamps are requested ON and the headlamp dimmer switch signal circuit is open, the BCM sends a pulse width modulated (PWM) ground signal though the headlamp low beam relay control circuit to the headlamp driver module which illuminates the low beam headlamps at a 100 percent intensity level. The right and left low beam circuits are independent and are fused separately in the underhood fuse block. The LOW HDLP-RT 10A fuse supplies voltage to the right low beam headlamp and the LOW HDLP-LT 10A fuse supplies voltage to the left low beam headlamp. The right and left headlamps are grounded at G103 and G107 respectively.

Your best bet mite be to have a qualified technician check it

Your best bet , take your vehicle to a qualified repair shop . Before you want to replace the BCM . . Professional tech would check for DTC'S - diagnostic trouble code's in the BCM before replacing part's that are not needed .

No signal at signal wire on relay ???? Which circuit wire mite that be ? Hooking up a factory or professional scan tool to view input data from the switch would also be a good step .

Headlamps
The headlamps may be turned ON 2 different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC, the headlamps will be OFF in daylight conditions, or low beam operation in low light conditions. Battery positive voltage is supplied to the low beam relay and the high beam relay in the underhood fuse block. When low beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the low beam relay. This activates the relay and the relay supplies voltage to the left hand low beam headlamp through the LH LOW BEAM fuse and to the right hand low beam headlamp through the RH LOW BEAM fuse. Ground for the left hand low beam headlamp is provided at G101. Ground for the right hand low beam headlamp is provided at G102. When high beam headlamps are requested, the body control module (BCM) supplies ground to the coil side of the high beam relay. This activates the relay and the relay supplies voltage to the left hand high beam headlamp through the LH HIGH BEAM fuse and to the right hand high beam headlamp through the RH HIGH BEAM fuse. Ground for the left hand high beam headlamp is provided at G101. Ground for the right hand high beam headlamp is provided at G102.

Headlamps Inoperative - Low Beams
Step
Action
Yes
No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference: Master Electrical Component List
1
Did you perform the Diagnostic System Check - Vehicle?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Vehicle
2
Place the headlamp switch in the HEADLAMP position.
Place the headlamp dimmer switch in the LOW position.
Do the low beam headlamps illuminate?
YES - Go to Testing for Intermittent Conditions and Poor Connections
NO - Go to Step 3
3
Disconnect the turn/headlamp switch connector C2.
Connect a 15-amp fused jumper between the headlamp low beam signal circuit and a good ground.
Do the low beam headlamps illuminate?
YES - Go to Step 4
NO - Go to Step 5
4
Inspect for poor connections at the harness connector of the turn/headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?
YES - Go to Step 7
NO - Go to Step 6
5
Repair an open or high resistance in the headlamp low beam signal circuit. Refer to Circuit Testing and Wiring Repairs .
YES - Did you complete the repair?
NO - Go to Step 7
--
6
Replace the turn/headlamp switch. Refer to Turn Signal Multifunction Switch Replacement .
YES - Did you complete the replacement?
NO - Go to Step 7
--
7
Operate the system in order to verify the repair.
Did you correct the condition?
YES - System OK
No - Go to Step 2

It's more then likely the dimmer switch .

DTC B2575
Circuit Description
The body control module (BCM) turns on the LOW BEAM relay when the ambient light sensor senses a dark condition or the low beam headlamps are requested ON. Battery positive voltage is supplied to the LOW BEAM relay at all times. The BCM grounds the LOW BEAM relay control circuit in order to activate the relay.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2575 Headlamp Control Circuit

B2575.01
Will set if there is a short to voltage in the low beam relay control circuit.
B2575.06
Will set if there is an open or short to ground in the low beam relay control circuit.

The headlamps are controlled by the BCM - body control module , do you know what that is ? The headlamp switch is a input to the BCM ,the BCM energizes relays to turn on the headlmps , low beam relay , high beam relay , DRL relay . These relay's are PCB - printed circuit board relay's ( non - serviceable ) If found to be bad the whole under hood fuse box would need to be replaced .
Low Beam Headlamp Operation
The low beam headlamps may be turned ON in 3 different ways:
• When the headlamp switch in the HEAD position for normal operations
• When the headlamp switch is in the AUTO position, for automatic lamp control (ALC)
• When the headlamp switch is placed in the AUTO position, with the windshield wipers ON in daylight conditions, after a 6 second delay
Battery voltage is applied at all times to the coil and switch sides of the LOW BEAM PCB Relay located in the underhood fuse block. When the headlamp switch is placed in the HEAD position, ground from G202 is applied through headlamps ON switch signal circuit to the body control module (BCM), signaling the headlamps ON request. In response to this signal, the BCM applies ground through the headlamp low beam relay control circuit energizing the low beam relay. With the relay energized, battery voltage is applied through the switch side of the relay, the left and right low beam fuses, and the low beam supply voltage circuits illuminating the low beam headlamps. Ground for the left headlamp is provided at G101 and the right headlamp at G100.

Do you know what B codes are ? BCM - DTC'S - diagnostic trouble codes , need a factory scanner or professional one to view these codes , not autozone or advance etc....Having a qualified repair shop check your vehicle would be your best bet.

DTC B2575 00: Headlamp Control Circuit

Circuit/System Description
The vehicle headlamps are controlled by the body control module (BCM) based on inputs from the headlamp switch and the turn signal/multifunction switch. The headlamp switch has four positions: Off, Auto, Park, and Headlamps. The default headlamp switch position is Auto, in which the BCM uses the ambient light sensor to determine when headlamps are needed. The Off portion of the headlamp switch is a momentary switch which overrides the automatic headlamps and will turn off the vehicle headlamps. When in the Off position, the headlamp switch grounds the headlamp switch headlamps off signal circuit, prompting the BCM to turn off the headlamps. The Park position of the headlamp switch will only illuminate the vehicle parking lamps. The Headlamp position of the headlamp switch will illuminate both the parking lamps, as well has the headlamps. With the headlamp switch in the Headlamp position, the headlamp switch headlamps on signal circuit is grounded, prompting the BCM to turn on the headlamps, regardless of other factors such as ambient light.
The headlamp high beams are controlled through the flash to pass switch and the headlamp dimmer switch, both located in the turn signal/multifunction switch. The flash to pass switch is a momentary type switch, designed to illuminate the high beams as long as the switch is held. With the switch closed, the flash to pass switch signal circuit is grounded, prompting the BCM to turn on the high beam lamps. The headlamp dimmer switch allows the operator to select between full time high or low beam operation. Unlike the flash to pass switch, it is not a momentary switch. When the headlamp dimmer switch is in the high beam position, the headlamp dimmer switch high beam signal circuit is grounded. This prompts the BCM to turn on the high beam lamps.
The BCM controls the headlamps based on the inputs explained above. When a low beam request is received, the BCM grounds the headlamp low beam relay control circuit. This energizes the coil in the LOW BEAM PCB relay, causing the relay switch to close. This then applies B+ to both low beam headlamps through the LT LO BEAM and RT LO BEAM fuses, illuminating the low beam headlamps. When a high beam request is received, the BCM grounds the headlamp high beam relay control circuit. This energizes the coil in the HIGH BEAM PCB relay, causing the relay switch to close. This then applies B+ to both high beam headlamps through the LT HI BEAM and RT HI BEAM fuses, illuminating the high beam headlamps

High Beam Headlamp Operation
Battery voltage is applied at all times to the coil and switch sides of the HIGH BEAM PCB Relay located in the underhood fuse block. When the headlamp dimmer switch is placed in the high beam position, the headlamp dimmer switch signal circuit to the BCM is pulled low signaling the headlamp high beam request. In response to this signal, the BCM applies ground through the high beam relay control circuit energizing the high beam relay. With the high beam relay energized, battery voltage is applied through the switch side of the relay, the left and right high beam fuses, and the high beam supply voltage circuits illuminating the high beam headlamps. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator. Ground for the left headlamp is provided at G101 and the right headlamp at G100.

seems you have several different problems. High beam working and no low beams=dimmer switch is bad. Reverse lamp not working=bulb socket bad,wiring broke,bad ground at back
Brake light on drivers side stuck on=brake light switch

No it is another circuit. Check theat you hav voltage at the high beam relay, in and out. If not you have a wiring problem between ther and the switch.

Both your low beam and your high beam is protected by the same fuse, so it makes sense that the fuse is OK if the high beam is working on the passenger side. There are 3 fuses for the headlamps. Fuse #13 in the Battery Junction Box (20 Amp). If this fuse is blown, the headlamp relay will not have any power and neither high nor low beam on either side will work (you will have no headlamps at all) Then there is Fuses #2 and #3 (15 Amp) in the Battery Junction Box. #2 goes to the left low and high beam and #3 goes to the right low and high beam.
The headlamp switch uses a SINGLE CIRCUIT to control BOTH sides at the same time, so if one side works, the switch cannot be the problem. The headlamp relay provides power for fuses #2 and #3 and we already ascertained that these fuses must have power since we have working lights on both sides, so the relay cannot be the problem. A replacement bulb has already been tried, so that pretty much leaves us with a bad lamp socket. (Most likely cause) or a bad connection at splice #S122, which is located in the main wiring harness near the breakout for the left headlamp. (RED/BLACK wire)

For Audi A4 the fuse box is located on the left side of dashboard behind a plastic cover (for left hand steering wheel vehicle). On inner face of the plastic cover you will find the fuse diagram.
First fuse on first row from left upper corner is Fuse Nr.20 = F20 (15A) - RH headlamp low beam, headlamp adjustment.
First fuse on second row from left upper corner is Fuse Nr.21 = F21 (15A) - LH headlamp low beam, headlamp adjustment.

do your flash to pass lamps light when you pull the stalk towards you? If yes, the bulbs are ok.
Do the hig beams work?
Your headlamps have sepaerate fuses for each headlamp and you have a low beam relay and a high beam relay under the hood in the black box.
If everything is out, I suspect a bad headlamp switch.
Check car-part.com and look on page with * for cheapest price.

Your owner manual will identify fuses & relays.

PS, You did not recently instal high current bulbs did you? If yes, put originals back in.

HEADLAMPS

The voltage is supplied to the lamp switch through a fuse. This fuse is located in the central junction box in the left-hand footwell.
When the headlamps are switched on, a voltage is supplied to the high beam/low beam switch and to the low beam relay. The relay for the low beam is located in the battery junction box (BJB) in the engine compartment.
If the high beam/low beam switch is set to "low beam", then a voltage is supplied through the low beam relay to the low beam part of the headlamp assembly. The left and right-hand low beams are fused separately. The fuses are located in the battery junction box (BJB) in the engine compartment.
If the high beam/low beam switch is set to "high beam", then a voltage is supplied through the high beam relay to the high beam part of the headlamp assembly. The left and right-hand high beams are fused separately. The fuses are located in the battery junction box (BJB) in the engine compartment.

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Lamp Switch
Removal

1. CAUTION: Disconnect the battery ground cable. For additional information, refer to Section 414-01 .
   Remove the lower driver's side footwell trim.

1. Detach the lamp switch bezel.
   • Remove two screws.

1. Remove the light switch.
   • Remove three screws.
• Disconnect the electrical connector