The headlamps on my Mazda MX5 do not work. The full beam is still functioning and one of the halogen bulbs is working. I've checked the bulbs, the fuses and the relay and all appears to be working.

This is a useful wiring diagram. I would say try swapping the relays over first and see if Low Beams now work and High Beams don't.

Other possibilities are two failed bulbs, or a broken connector. A good test meter should be able to trace this.

https://boostedmedia.net/automotive/videos/tech-videos/mx5-miata-headlight-wiring/


It does appear to be a known issue

https://www.google.com/search?q=2013+mazda+miata+no+low+beam+headlight

This suggests the combination switch

https://forum.miata.net/vb/showthread.php?t=531436

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perhaps its the wiring leading to the lamp itself. I don't know about your car, but when i fixed mine, there are 3 lines leading to the headlights. perhaps the one leading to the regular light is probably cut or burnt. Try to have it checked with a car electrician if you're not comfortable fiddling with you car's wiring!

More often than not. headlights are usually 0n a fusible link or automatic breaker. and they controll both head lights at the same time. try checking the connector at the rear of the light unit. If its one of the later one piece covered units. the problem is most likly the halogen bulb. most reputable parts houses,such as AutoZone will check it out for you.
Good luck !

Removal & Installation
Bulb Replacement
To Remove:

CAUTION
Halogen bulbs contain pressurized gas.
Mishandling a bulb may result in the bulb shattering into flying glass
fragments.

CAUTION
Make sure to wear eye protection when
handling a halogen bulb.

CAUTION
Do not touch the glass of a halogen bulb,
only handle the bulb by the base.

CAUTION
Do not allow a halogen bulb to come into
contact with dirt or moisture.

CAUTION
Make sure to dispose of a used halogen bulb
properly.

CAUTION
Do not allow children to handle halogen
bulbs.

1. Turn the lamp switch to the off position.
   
2. Make sure the bulb is cool before changing.
   
3. Remove the headlamp assembly from the headlamp panel.
   
4. Remove the rear access cover from the headlamp assembly.
   
5. Disconnect the headlamp connector.
   
6. Remove the bulb from the headlamp assembly by rotating the bulb and socket
   counterclockwise.

To Install:

1. Connect the headlamp connector.
   
2. Install the bulb into the headlamp assembly by rotating the bulb and socket
   clockwise.
   
3. Install the rear access cover onto the headlamp assembly.
   
4. Install the headlamp assembly into the headlamp panel.

Headlamp Assembly
Chevrolet
To Remove:






Headlamp Assembly (Chevrolet)

1. Remove the grille from the front of the vehicle.
   
2. Release the headlamp assembly retaining tabs.
   
3. If equipped, disconnect the headlamp leveling motor connector.
   
4. Disconnect the headlamp connector.
   
5. Remove the park/turn and side marker bulb sockets from the headlamp
   assembly.
   
6. Remove the headlamp assembly from the headlamp panel.

To Install:

1. Place the headlamp assembly into the headlamp panel.
   
2. Install the park/turn and side marker bulb sockets into the headlamp
   assembly.
   
3. Connect the headlamp connector.
   
4. If equipped, connect the headlamp leveling motor connector.
   
5. Lock the headlamp assembly retaining tabs.
   
6. Install the grille onto the front of the vehicle.

GMC, Oldsmobile, Buick, Isuzu, and Saab
To Remove:






Headlamp Assembly (GMC, Saab, Oldsmobile, and Buick)

1. Release the headlamp assembly retaining tabs.
   
2. Disconnect the headlamp connector.
   
3. Remove the park/turn bulb socket from the headlamp assembly.
   
4. For GMC, Saab, Oldsmobile, and Isuzu vehicles, remove the side marker bulb
   socket from the headlamp assembly.
   
5. Remove the headlamp assembly from the headlamp panel.

To Install:

1. Place the headlamp assembly into the headlamp panel.
   
2. For GMC, Saab, Oldsmobile, and Isuzu vehicles, install the side marker bulb
   socket into the headlamp assembly.
   
3. Install the park/turn bulb socket into the headlamp assembly.
   
4. Connect the headlamp connector.
   
5. Lock the headlamp assembly retaining tabs.

Have you tried to change the headlights?

REMOVAL & INSTALLATION Sealed Beam NOTE: If vehicle is equipped with headlamp doors turn the headlight switch ON. Open the hood and locate the power distribution center. This center is located in the front of the left front strut tower. Remove the cover from the center and remove the Headlamp Close Relay. This will prevent the headlamp doors from closing to provide easier servicing. Turn the headlight switch to OFF, then perform this repair.

1. Remove the headlight bezel.
2. Unhook the spring from the headlight retaining ring if so equipped.
3. Unscrew the retaining ring and remove it. NOTE: Do not disturb the two long aiming screws. Conventional and Halogen headlamp sealed beams units are interchangeable in pairs, but it is recommended that they not be mixed together (one halogen and one conventional). It is fine to upgrade from conventional bulbs to halogen, but do not change from halogen bulbs to conventional bulbs, especially if the vehicle came equipped with halogen bulbs.
   
4. Unplug the old sealed beam from the engine electrical wiring harness.
5. Extract the old bulb from its mounting bracket. To install:
   
6. Connect the replacement bulb and install it into the receptacle (check operation of headlight before completing repair).
7. Install the retaining ring and secure it in place with the retaining screws. Connect the spring.
8. Install the headlight bezel.

Aero Headlamp Aero headlamp systems use replaceable halogen bulbs that are mounted in aerodynamic, molded plastic lens reflector assemblies. NOTE: Lens fogging is a normal condition and does not require service, as moisture will vent from tubes behind the lens on Aero headlamp-type system. EXCEPT PREMIER AND MONACO It may be necessary to remove the entire headlamp assembly if enough access cannot be gained otherwise.

1. Locate and remove the wire connector behind the headlamp assembly in the engine compartment. It may be necessary to remove certain items in the engine compartment to gain access to the bulb wires.
2. Rotate the bulb retaining ring counterclockwise 1?4 turn and remove the ring, bulb and bulb holder from the lens assembly. The bulb holder has alignment notches. NOTE: Do not touch the bulb with bare fingers or any possibly oily surface, since reduced bulb life may result! Fig. 1: To remove the light bulb, first unplug the headlight electrical connector, then . . .
   Fig. 2: . . . remove the light bulb socket retaining ring
   Fig. 3: Rotate the light bulb socket 1?4 turn counter-clockwise, then pull it straight out of the lens assembly
   To install:
   
3. Wearing gloves or holding the replacement bulb with a cloth rag to keep oil off of the bulb surface, insert the bulb into the rear hole of the headlamp assembly. Make certain that the alignment grooves and tabs line up, push the light bulb into the assembly until seated flush, then turn the bulb clockwise 1?4 turn.
4. Plug the electrical light bulb wiring harness into the new light bulb. Install any items removed from the engine compartment.

PREMIER AND MONACO Unlike the other vehicles covered by this manual, the removal and installation of the headlamp bulbs in the Premier and Monaco models requires the extraction of the entire headlamp lens assembly.

1. Remove the grille-to-headlamp assembly attaching screws.
2. Disconnect the headlamp aiming cable from the aiming screw end.
3. Remove the headlamp assembly attaching bolts from above and behind the lamp assembly and separate the lamp assembly from the vehicle.
4. Unplug the headlamp wire connector. NOTE: Do not touch the bulb with bare fingers or any possibly oily surface, since reduced bulb life may result!
   
5. Rotate the socket counterclockwise 1?4 turn and pull the socket from the back of the lens assembly. Fig. 4: Remove the bezel retaining screws to loosen the headlamp assembly - Premier and Monaco
   Fig. 5: Detach the headlamp wire connector - Premier and Monaco
   Fig. 6: Once the headlamp assembly has been removed from the vehicle, the various light bulbs can easily be removed - Premier and Monaco
   To install:
   
6. Wearing gloves or holding the replacement bulb with a cloth rag to keep oil off of the bulb surface, insert the bulb into the rear hole of the headlamp assembly. Make certain that the alignment grooves and tabs line up, push the light bulb into the assembly until seated flush, then turn the bulb clockwise 1?4 turn.
7. Plug the headlamp wire connector back into the headlamp bulb.
8. Install the assembly into the vehicle and secure in place with the mounting bolts.
9. Connect the headlamp aiming cable to the aiming screw end.
10. Install the grille-to-headlamp assembly attaching screws.

f
GM Century/Lumina/Grand Prix/Intrigue 1997-2000 Repair Guide
Headlamps REMOVAL & INSTALLATION
Sealed Beam

1. Open the hood.
2. Disconnect the negative battery cable.
3. Remove the headlamp bezel retainers and bezel.
4. Remove the spring from the bottom edge of the headlamp assembly.

NOTE Do not apply pressure to the plastic bubble of the vertical aim indicator.

1. Detach the electrical connector from the assembly.
2. Unfasten the two screws from the headlamp retaining ring.
3. Rotate the retaining ring away from the headlamp.
4. Remove the headlamp from the vehicle.
   

To install:

1. Position the headlamp and retaining ring and secure with the two retaining screws. Tighten the screws to 18 inch lbs. (2 Nm).
2. Attach the electrical connector to the assembly.
3. Install the spring to the bottom of the headlamp assembly.
4. Install the headlamp bezel and retainers.
5. Connect the negative battery and test the lights for proper operation.

Composite Headlamps
The headlamps used on the majority of vehicles covered by this guide are called "composite lamps". Unlike the glass sealed beam units used on older vehicles, these headlamps are made of special plastic using small halogen gas bulbs. The bulbs are replaceable, but they do require special handling.

CAUTION Halogen bulbs contain a gas under pressure. Handling a bulb improperly could cause it to shatter into flying glass fragments. Always allow the bulb to cool before removal. Always use the following precautions to help avoid personal injury.
Turn the light switch OFF and allow the bulb to cool before changing bulbs. Leave the switch OFF until the bulb replacement procedure is complete.
Always wear eye protection when changing a halogen bulb.
Handle the bulb only by its base. Avoid touching the glass. Do not drop or scratch the bulb.
Keep the bulb away from moisture.
Place the used bulb in the new bulb's carton and dispose of it properly. Keep halogen bulbs out of reach of children.
Depending on the installation, the low-bean and the high-beam halogen bulbs may actually be removable without removing the entire composite headlamp assembly. Look your application over carefully to see there is enough room behind the headlamp to fit your hand to remove the bulb holder. Since removing the composite headlamp assembly is not difficult, the following procedure assumes that the headlamp is being removed from the vehicle for halogen bulb service.

1. Raise the hood and look at the headlamp installation. On some applications, the headlamp is retained by screws and some molded tabs that slip into slots in the sheetmetal mounting bracket. On other applications, two U-shaped clips may hold the headlamp in place. Remove the headlamp retainers and gently work the headlamp free of the vehicle.
2. If the wiring harness is so short that it is difficult to work on the headlamp, simply unplug the electrical connector from the headlamp assembly.
3. The halogen bulb may have a large, knurled plastic ring that retains the socket to the headlamp. Turn this ring to detach it and remove the socket with the halogen bulb.
4. Remove the burned-out bulb and discard safely.

WARNING Do not touch the glass bulb with your fingers. Oil from your fingers can severely shorted the life of the bulb. If necessary, wipe off any dirt or oil from the bulb with rubbing alcohol before completing installation.

1. Take great care not to touch the new replacement halogen bulb as oil from your skin will burn when the bulb is turned on and may damage the glass, shortening the life of the bulb. Use a clean, dry paper towel to handle the bulb.
2. Installation is the reverse of the removal procedure.
3. Verify that the lights work correctly.

Headlamp adjustment may be temporarily made using a wall, as described below, or on the rear of another vehicle. When adjusted, the lights should not glare in oncoming car or truck windshields, nor should they illuminate the passenger compartment of vehicles driving in front of you. These adjustments are rough and should always be fine-tuned by a repair shop which is equipped with headlamp aiming tools. Improper adjustments may be both dangerous and illegal.




Fig. Typical composite headlamp aiming rods





Fig. Typical horizontal and vertical adjuster locations




Fig. Vehicle headlamp aiming device (RH)-Buick shown, others similar
Before removing the headlamp bulb or disturbing the headlamp in any way, note the current settings in order to ease headlamp adjustment upon reassembly. If the high or low beam setting of the old lamp still works, this can be done using the wall of a garage or a building:

1. Park the vehicle on a level surface, with the fuel tank about 1 / 2 full and with the vehicle empty of all extra cargo (unless normally carried). The vehicle should be facing a wall which is no less than 6 feet (1.8m) high and 12 feet (3.7m) wide. The front of the vehicle should be about 25 feet from the wall.
2. If neither beam on one side is working, and if another like-sized vehicle is available, park the second one in the exact spot where the vehicle was and mark the beams using the same-side light. Then switch the vehicles so the one to be aimed is back in the original spot. It must be parked no closer to or farther away from the wall than the second vehicle.
3. Perform any necessary repairs, but make sure the vehicle is not moved, or is returned to the exact spot from which the lights were marked. Turn the headlamps ON and adjust the beams to match the marks on the wall.
4. Have the headlamp adjustment checked as soon as possible by a reputable repair shop.

Hope helps with this (remember rated this) Good luck.

Headlamp Bulb: Service and Repair
REMOVAL PROCEDURE
1. Make sure the headlamp switch is in the OFF position.
CAUTION: Halogen bulbs contain gas under pressure. Handling a bulb improperly could cause it to shatter into flying glass fragments.
To help avoid personal injury:
- Turn off the lamp switch and allow the bulb to cool before changing the bulb. Leave the lamp switch off until the bulb change is
complete
- Always wear eye protection when changing a halogen bulb.
- Handle the bulb only by its base. Avoid touching the glass.
- Do not drop or scratch the bulb.
- Keep dirt and moisture off the bulb.
- Place the used bulb in the new bulb's carton and dispose of it properly.
- Keep halogen bulbs out of the reach of children
NOTE: Avoid touching the bulb or letting the bulb come in contact with anything damp. Oil from your skin or moisture on the bulb can cause
the bulb to explode when the bulb is turned on. It either comes in contact with the bulb, clean the bulb with alcohol or a suitable degreaser and
wipe the bulb dry.
2. Remove the bulbs from the headlamp capsules by reaching from the engine compartment and by twisting the bulb counterclockwise.
3. Remove the 2 long screws from the top of the radiator support.
4. Pull forward the headlamp assembly (3).
5. Disconnect the electrical connector (2) from the burned out bulb assembly (1).
INSTALLATION PROCEDURE
IMPORTANT:
- Replace a high beam bulb with another high beam bulb. The high beam bulb has a red gasket.
- Replace a low beam bulb with another low beam bulb. The low beam bulb has a gray tip and a yellow gasket at the base.
1. Install the new bulb assembly (1) into the headlamp assembly (3).
Twist clockwise the bulb assembly.
2. Seat the bulb assembly with the connector facing down.
3. Connect the electrical connector (2) to the bulb assembly.
4. Install the headlamp assembly.
5. Install the 2 long screws through the top of the radiator support.
6. Tighten the screws.

Headlamp Removal & Installation Bulb Replacement To Remove:
CAUTION
Halogen bulbs contain pressurized gas. Mishandling a bulb may result in the bulb shattering into flying glass fragments.
CAUTION
Make sure to wear eye protection when handling a halogen bulb.
CAUTION
Do not touch the glass of a halogen bulb, only handle the bulb by the base.
CAUTION
Do not allow a halogen bulb to come into contact with dirt or moisture.
CAUTION
Make sure to dispose of a used halogen bulb properly.
CAUTION
Do not allow children to handle halogen bulbs.

1. Turn the lamp switch to the off position.
2. Make sure the bulb is cool before changing.
3. Remove the headlamp assembly from the headlamp panel.
4. Remove the rear access cover from the headlamp assembly.
5. Disconnect the headlamp connector.
6. Remove the bulb from the headlamp assembly by rotating the bulb and socket counterclockwise.

To Install:

1. Connect the headlamp connector.
2. Install the bulb into the headlamp assembly by rotating the bulb and socket clockwise.
3. Install the rear access cover onto the headlamp assembly.
4. Install the headlamp assembly into the headlamp panel.

HEADLAMP BULB REPLACEMENT

REMOVAL PROCEDURE

CAUTION: Halogen bulbs contain gas under pressure. Handling a bulb improperly could cause it to shatter into flying glass fragments. To help avoid personal injury:

• Turn off the lamp switch and allow the bulb to cool before changing the bulb.
• Leave the lamp switch OFF until the bulb change is complete.
• Always wear eye protection when changing a halogen bulb.
• Handle the bulb only by its base. Avoid touching the glass.
• Keep dirt and moisture off the bulb.
• Properly dispose of the used bulb.
• Keep halogen bulbs out of the reach of children .

NOTE : Avoid touching the bulb or letting the bulb come in contact with anything damp. Oil from your skin or moisture on the bulb can cause the bulb to explode when the bulb is turned on. If either comes in contact with the bulb, clean the bulb with alcohol or a suitable degreaser and wipe the bulb dry.

1. Open the hood.
2. Remove the headlamp. Refer to Headlamp Replacement .

1. Remove the access cover from the rear of the headlamp.
2. Disconnect the electrical connector from the socket.
3. Rotate the bulb and socket counter clockwise in order to remove the bulb and socket from the housing.
4. Disconnect the electrical connector from the socket.
5. Remove the bulb and socket from the headlamp.

INSTALLATION PROCEDURE

IMPORTANT :

• Replace a high beam bulb with another high beam bulb. The high beam bulb has a black socket.
• Replace a low beam bulb with another low beam bulb. The low beam bulb has a gray tip and a grey socket.
  
  1. Position the bulb and socket to the headlamp.
  2. Connect the electrical connector to the socket.
  3. Install the bulb and socket to the housing by rotating the bulb and socket clockwise, locking the retaining tabs to the housing.
  4. Install the access cover to the rear of the headlamp assembly
  5. Install the headlamp

REMOVAL PROCEDURE

1. Open the hood.
2. Remove the headlamp.
3. Rotate the bulb and socket counter-clockwise in order to remove the bulb and socket from the housing.
4. Remove the side marker bulb (3) or turn signal/park bulb (4) from the socket.

INSTALLATION PROCEDURE

1. Install the side marker bulb (3) or turn signal/park bulb (4) to the socket.
2. Wipe the bulb with a clean cloth to ensure the bulb is free of any dirt or oil.
3. Install the bulb and socket to the headlamp by rotating the bulb and socket clockwise, locking the retaining tabs to the headlamp.
4. Install the headlamp.

The adjustment screws/nuts should be located either on the top of the headlamp assembly, behind the headlamp assembly, or near the frame rail by the radiator support.

You will have vertical adjustment screws for each independent beam (separate highs and separate lows, but will be same screw if highs and lows are the same bulb). You may also have additional horizontal adjustment screws as well

Park your car on a level ground 30 feet from a wall and measure the height from the ground to the bulb and mark on a wall (do this for highs beams and low beams if the bulbs are separate, if highs and lows are the same bulb, only do it for the lows)

If the headlights read VOR, then aim the brightest part or cutoff part just below the mark on the wall. If it says VOL or nothing, aim them 2 inches below the mark on the wall.