Fog lights (FFL) are an integral element of safety in poor visibility conditions, but their display on the dashboard often raises questions among drivers. Why does the icon blink, why does it not go out after turning off the headlights, or why does it not light up at all when activated? These symptoms can signal either simple forgetfulness or serious problems in the car’s electrical circuit.

Many people confuse fog light icon with high beam or size indicators - especially on foreign cars, where the pictograms may differ from the usual Russian standards. Meanwhile, ignoring the burning icon or its incorrect operation is fraught not only with a fine for improper use of lighting devices (under Part 3 of Article 12.20 of the Code of Administrative Offenses of the Russian Federation), but also with the risk of being left without lighting in fog or rain. Let's figure out how to decipher instrument panel signals and what to do in case of malfunctions.

In this article you will find:

  • 🔍 Photo and description all variants of PTF badges on different car brands
  • ⚡ Step by step instructions to turn on/off fog lights
  • ⚠️ Deciphering alarm signals (flashing, constant light)
  • 🛠️ Diagnostics and repair (fuses, relays, lamps)
  • 📜 Legal nuances use of PTF according to traffic rules 2026

What does the fog light icon look like on the instrument panel?

Standard PTF badge is a stylized image of a headlight with wavy lines (symbolizing fog) and three oblique stripes pointing down and to the left. However, its appearance may vary depending on the make and model of the car:

  • 🚗 Domestic cars (Lada, GAS, UAZ): the classic yellow icon with three stripes, often combined with a switch on the steering column.
  • 🚘 European brands (Volkswagen, Renault, Peugeot): the icon can be green (front PTF) or yellow (rear), with more rounded shapes.
  • 🚙 American and Asian cars (Toyota, Ford, Hyundai): often used as an abbreviation FOG or FRONT FOG next to the icon.
  • 💡 Premium brands (BMW, Mercedes, Audi): The icon can be integrated into the number pad with animation (for example, flashing bars when activated).

On some vehicles (for example, Skoda Octavia or Kia Rio) the icon for the front and rear fog lights differs in the direction of the stripes: for the front ones they are directed down-left, at the rear - down-right with a red background. If you see an unfamiliar icon, check instruction manual — there is always a legend of the designation.

📊 What PTF badge is on your car?
Classic three stripes
With the inscription FOG
Digital animation
I don't know what it looks like

Where is the button to turn on the fog lights?

The location of the PTF switch depends on the design of the vehicle. In most cases, the fog lights are controlled by:

  1. Steering column switch (more often on European and Japanese cars). For example, on Toyota Corolla or Volkswagen Passat you need to turn the light switch ring one click on my own behalf to turn on the front PTFs.
  2. Separate button on the panel (typical for Korean and American cars). On Hyundai Solaris or Ford Focus This is a round button with a fog icon located to the left of the steering wheel.
  3. Multimedia screen (in modern cars, for example, Tesla or Nissan Leaf). Here control is carried out through the menu Lighting → Fog Lights.

Important nuance: on most cars fog lights can only be turned on when the ignition is on and the side lights are on. If the icon on the panel does not light up, first check whether the headlights are on (green indicator on the dash).

Ignition is on (key in ON position)

Side lights activated (green indicator on panel)

The light switch is in the "auto" or "dimensions" position

No blown fuses (see "Diagnostics" section)

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Why the fog light icon is on: decoding the signals

The PTF indicator on the dashboard may behave differently. Let's decipher each option:

Icon behavior Possible reason Actions
Constantly on (yellow/green) Fog lights are included as standard Turn off the switch or check that it is locked
Flashes 1-2 times per second A bulb in one of the headlights has burned out. Check the lamps (see the "Diagnostics" section) and replace the faulty one
Flashes quickly (3+ times per second) Short circuit or malfunction of the light control unit Contact an auto electrician for diagnosis. BCM (Body Control Module)
Lights up red Malfunction in the rear fog lamp circuit (if any) Check the fuse F30 (typical designation) and rear PTF relay
Doesn't light up when turned on Faulty switch, fuse, or broken wire Check the circuit according to the diagram (see below)

Critical information: if the PTF icon flashes simultaneously with the indicator ABS or ESP, this may indicate a problem in the vehicle's can-bus. In this case, complex diagnostics are required, since the malfunction may affect several systems.

⚠️ Attention: On some vehicles (for example, Renault Duster or Nissan Qashqai) the PTF icon may light dimly when the low beam is on - this is normal and does not require intervention. However, if the brightness of the indicator changes chaotically, this is a sign of unstable voltage in the on-board network.

Fault diagnosis: step-by-step instructions

If the fog light icon behaves abnormally, follow this algorithm:

1. Checking lamps and contacts

  • 🔦 Open the hood and inspect headlight glass for cracks or moisture inside.
  • 💡 Remove the lamp (on most cars - socket H11 or H8) and check the filament for a break.
  • 🔌 Clean the contacts in the cartridge from oxidation (use WD-40 or alcohol).

2. Checking fuses and relays

The location of the fuses is indicated in instruction manual or on the fuse box cover. Typical designations:

  • 🔥 PTF fuse: F15 (10-15A) - front, F20 (7.5-10A) - rear.
  • ⚡ Fog light relay: K7 or K9 (on the relay block diagram).

To check the fuse, use a multimeter in the "continuity" mode or visually inspect the thread. The relay is checked by replacing it with a known good one (for example, from turn signals).

How to test a circuit with a multimeter?

1. Set the multimeter to resistance measurement mode (200 ohms).

2. Connect the probes to the contacts of the fuse or lamp connector.

3. The resistance of a working circuit should be close to 0 ohms. If it shows “1” (break), look for damage to the wire.

3. Switch and wiring diagnostics

If the lamps and fuses are working, the problem may lie in:

  • 🔄 Steering column switch: disassemble it and check the contacts (a common problem on VAZ 2110-2112).
  • 🔌 Broken wire: Inspect the wiring harness from the fuse box to the headlights (especially where there are kinks).
  • 🖥️ Light control unit (BCM): requires diagnostics by a scanner (for example, Launch X431).
⚠️ Attention: On vehicles with xenon PTF (for example, Audi A6 or BMW 5-series) replacing lamps yourself without disconnecting the battery can lead to failure of the ignition unit! Be sure to remove the negative terminal before work.

Connection diagrams for fog lights

A typical PTF connection diagram includes:

  1. Power source (battery) → fuse → relay.
  2. Relay → panel switch → lamps.
  3. Feedback from control unit (on modern cars) for indication on the tidy.

Below is a simplified diagram for most cars:



Battery (+12V)


│


▼


[Fuse F15] → [Relay K7] → [Switch] → [PTF lamps]


│ │


▼ ▼


Weight (body) BCM (indication)

On vehicles with automatic light (for example, Volkswagen Tiguan or Skoda Kodiaq) is added to the chain light sensor, which can block the activation of the PTF with sufficient visibility.

💡

If after replacing the PTF lamp the icon continues to blink, try resetting the error by disconnecting the battery for 10 minutes. On some cars (for example, Ford Mondeo) this resets errors in the control unit.

According to Traffic rules of the Russian Federation (clauses 19.4 and 19.7), fog lights can be used:

  • 🌫️ In conditions insufficient visibility (fog, rain, snowfall) - how in addition to low or high beam.
  • 🚗 On unlit sections of roads together with low beam (instead of high beam).
  • 🚛 Outside populated areas in dark time of day on vehicles of categories M1 and N1 (passenger cars and trucks up to 3.5 tons).

Prohibited:

  • ❌ Use PTF instead of daytime running lights (fine 500 rubles under Part 1 of Article 12.20 of the Administrative Code).
  • ❌ Turn on rear fog lights only without front ones (fine 500 rubles).
  • ❌ Install lamps blue or red (deprivation of rights for 6-12 months under Part 3 of Article 12.5 of the Administrative Code).
⚠️ Attention: Since 2023, technical regulations have been in force in Russia, obliging the use of only certified lamps in foglights. Replacement with LEDs (LED) or xenon (HID) in standard reflectors are considered a malfunction if they are not provided by the factory!
💡

Fog lights must be adjusted so that the light beam does not blind oncoming drivers. Check the adjustment at a service station every 20,000 km or after replacing lamps.

Frequently asked questions about fog lights

❓ Is it possible to drive with the PTF on during the day in the city?

No, this is a violation of clause 19.4 of the traffic rules. Fog lights can be used during the day only in low visibility conditions (fog, snowfall) or in unlit areas outside the city. In other cases you need to enable daytime running lights or low beam.

❓ Why did the fog lights stop working after washing?

Most likely, water got into the headlight, which led to:

  • Short circuit (fuse blown).
  • Oxidation of lamp contacts.
  • Damage to the reflector (corrosion).

Solution: dry the headlight (you can use a hairdryer), check the fuse and contacts. If the problem persists, you need to sealing headlight joints silicone.

❓ How to adjust fog lights yourself?

To adjust you will need:

  1. Flat area and a wall at a distance of 5 meters.
  2. Mark the center of each headlight on the wall and draw a horizontal line 10 cm below the height of the lamps.
  3. Turn on the PTF and adjust the screws on the headlight so that the upper limit of the light spot coincides with the line.

On some cars (for example, Toyota RAV4) adjustment is carried out through the on-board computer menu (Settings → Lighting → Fog Light Adjustment).

❓ Is it possible to install LED lamps in fog lights?

Only if they certified for your car model and are marked ECE R19 (for PTF). Otherwise:

  • Traffic police officers can fine you 500 rubles. for non-compliance GOST R 51709-2001.
  • LEDs without a corrector can blind oncoming drivers due to incorrect luminous flux.

Legal options: installation standard LED-PTF (for example, on Audi A4 B9) or replacing the entire headlight with a certified one.

❓ Why does the PTF icon light up, but the headlights do not work?

Probable reasons:

  • 🔌 Break ground wire (check the attachment to the headlight body).
  • 💡 Burnt out both lamps simultaneously (rarely, but possible).
  • 🖥️ Defective light control unit (requires diagnostics with a scanner).
  • 🔋 Low voltage in the on-board network (check the battery and generator).

Start by checking fuse and relay, then test the circuit with a multimeter.