Heater fuse <em>Nissan Sunny FB15</em>: location, ratings and replacement

Nissan Sunny FB15 (1990–1995) is a legendary Japanese sedan, but even it has problems with the heating system over time. One of the most common malfunctions is failure heater fuse, which leads to failure of the fan, airflow or a complete lack of heat in the cabin. In this article we will look at where the heater fuse is located, how to check it, replace it and avoid common mistakes during repairs.

It is important to understand that in FB15 The heating system is connected not only to the fuse, but also to the relay, thermostat and electric motor. However, in 80% of cases, the problem lies precisely in a blown fuse - replacing it takes 5 minutes, but requires knowledge of the exact location and rating. We have collected current data on all modifications Sunny FB15, including versions with and without air conditioning.

Where is the heater fuse located? Nissan Sunny FB15

B FB15 The heater fuse is located in main fuse box, which is located to the left of the steering column, under the instrument panel. To access it, you must:

1. Open the driver's door and sit in the seat.
2. Find the plastic cover of the fuse box (it has the inscription FUSE or FUSE BOX).
3. Carefully pry the cover with a screwdriver or your fingers and remove it.

Inside the block the heater fuse is marked as HEATER or BLOWER (depending on the year of manufacture). Its denomination is 20A or 25A (more details in the table below). Models with air conditioning may have an additional fuse for climate control, but it does not affect the operation of the heater itself.

⚠️ Attention: On some versions FB15 (for example, for the Japanese market) the heater fuse may be in additional block under the hood. If it is not in the car, check the mounting block next to the battery.

In order not to be confused, rely on the color: the heater fuse is usually yellow (20A) or transparent (25A) color. If in doubt, check the diagram on the back of the unit cover.

Heater fuse ratings and diagrams for different versions FB15

The fuse rating depends on the configuration and year of manufacture of the car. Below is a table with current data for Nissan Sunny FB15:

Modification	Year of manufacture	Fuse rating	Designation on the block	Additional fuses
Without air conditioning	1990–1992	20A	HEATER (№15)	—
With air conditioning	1993–1995	25A	BLOWER (№18)	A/C RELAY (10A, No. 22)
European version (GA15DE)	1991–1994	20A	HEATER (№17)	IGNITION (15A, No. 10)
Japanese version (SR18DE)	1990–1995	25A	BLOWER MOTOR (№20)	A/C CLUTCH (10A, No. 25)

If your version is not listed in the table, please note inscriptions on the fuse box cover — there is always an up-to-date diagram there. The denomination can also be determined by color:

• 🟡 Yellow - 20A (the most common option).
• ⬜ Transparent/white — 25A (for versions with air conditioning).
• 🔴 Red — 10A (auxiliary, for fan relay).

In models with climate control an additional fuse can be installed on 10A to control the dampers. Its failure will not turn off the stove completely, but will lead to improper operation of the air distribution.

How to check a fuse without a tester?

If you don't have a multimeter at hand, you can visually inspect the fuse for burnt thread inside. To do this, remove it from the socket and look at the light: if the thread is broken, the fuse has burned out. However, this method is not always accurate, since sometimes the break is invisible.

Causes of blown heater fuse and how to eliminate them

The heater fuse does not burn out just like that - it is a signal of a malfunction in the circuit. Main reasons:

1. Short circuit in wiring - the most dangerous problem. Most often it occurs due to frayed wires under the panel or oxidized contacts.
2. Fan motor wear - over time, the motor brushes wear out, and it begins to consume more current, which leads to the fuse burning.
3. Fan is dirty or jammed — leaves, dust or mechanical obstacles cause the motor to overload.
4. Faulty fan relay - if the relay is “stuck” in the closed state, the circuit remains energized even after the stove is turned off.

To prevent re-burnout, you must:

• 🔍 Check wiring for damage (especially in the bends under the panel).
• 🌀 Clear stove fan from debris (access to it is through the glove compartment or from the bottom of the panel).
• 🔧 Check fan relay (usually located near the fuse box).
• 📊 Measure current consumption stove motor (should be no more than 10–12A at maximum speed).

⚠️ Attention: If the fuse burns out immediately after replacement - do not install a fuse of a higher rating (for example, 30A instead of 20A). This may cause a fire in the wiring! In such a situation, it is urgent to look for a short circuit.

To diagnose a short circuit, disconnect the heater motor connector and check the circuit with a multimeter in continuity mode. If the short circuit remains, the problem is in the wiring; if it disappears, the fan motor is to blame.

Step-by-step instructions for replacing the heater fuse

Replacing a fuse is a simple procedure, but requires care. Follow the instructions:

1. Turn off the ignition and remove the key from the lock. This will prevent accidental shorting.
2. Remove the fuse box cover (as described above).
3. Find the heater fuse according to pattern or color (yellow/transparent).
4. Remove it with special forceps (they are usually attached to the block cover) or tweezers. Never use metal objects - this may damage the sockets.
5. Install a new fuse the same denomination. Insert it until it clicks.
6. Check the operation of the stoveby turning on the ignition and moving the fan control to the maximum position.

If the stove does not work after replacement, check:

• 🔌 Contacts in the fuse box - they can be oxidized.
• 🔄 Fan relay (usually located nearby, marked as BLOWER RELAY).
• 🔌 Ignition circuit fuse (sometimes affects the power supply to the stove).

If the fuse is blown again - do not repeat replacement, and look for the cause (short circuit or faulty motor). A temporary solution may be to install fuse insert with fuse elementwhich is easier to diagnose.

Common mistakes when replacing a heater fuse and how to avoid them

Even something as simple as replacing a fuse can be done incorrectly. Let's look at typical mistakes:

• 🔧 Using the wrong fuse rating - for example, installing 30A instead of 20A. This is fraught with melting of the wiring or failure of the electric motor.
• 🔌 Loose fuse installation - if it does not latch, the contact will be unreliable, which will lead to overheating.
• 🔍 Ignoring the cause of burnout - if you simply replace the fuse without diagnostics, it will burn out again.
• 🛠️ Damage to fuse box sockets — when removing with a screwdriver or knife, the contacts can be bent.

To avoid problems:

• 📋 Always check new fuse rating (written on the case).
• 🔧 Use plastic tongs from the fuse box kit.
• 🔍 After replacing, turn on the stove and check the fuse temperature by hand - if it gets hot, then there is a problem in the circuit.

⚠️ Attention: If there are traces of melting or burning in the fuse block, this is a sign serious short circuit. In this case, it is necessary to check the entire power supply circuit of the heater, including the wiring harnesses under the panel and in the engine compartment.

In models FB15 with automatic climate control sometimes not only the fuse burns out, but also diode in the control unit. In this case, the stove may only operate at one speed or may not respond to the regulator at all.

How to extend the life of the fuse and the stove in Nissan Sunny FB15

To avoid frequent fuse replacement and increase the life of your heating system, follow these tips:

• 🌬️ Clean the stove fan regularly from leaves and dust (it is enough to remove the glove compartment once a year and blow out the engine with compressed air).
• 🔧 Lubricate the fan bearings every 2–3 years (use heat-resistant lubricant, e.g. LIQUI MOLY Thermoflex).
• 🔌 Check your contacts in the fuse and relay box - oxidation increases resistance and leads to overheating.
• 🚗 Don't turn the stove on high immediately after starting the engine in winter - let the system warm up for 1-2 minutes.

It is also useful to check once a season thermostat operation - if it gets stuck in the open position, the engine will not warm up to operating temperature, and the heater will blow cold air. B FB15 The thermostat is located next to the pump and can be replaced in 15 minutes.

If you often drive off-road or in rainy weather, it is recommended to treat the fuse box contacts water-repellent lubricant (For example, CRC 2-26). This will prevent corrosion and accidental short circuits.

Alternative methods for diagnosing stove malfunctions

If replacing the fuse does not help, the problem may lie in other elements of the system. Perform additional diagnostics:

1. Check the fan relay — it should click when you turn on the stove. If there is no click, the relay is faulty.
2. Measure the voltage at the fan connector (should be 12V when the stove is on).
3. Check the resistance of the motor windings (the norm is 2–5 ohms). Infinite resistance indicates a break.
4. Inspect the fan speed resistor (located next to the motor). Often his contacts burn out.

To check the relay and motor you can use direct connection to battery:

1. Remove the connector from the fan motor.
2. Connect it directly to the battery (plus to plus, minus to minus).
3. If the motor starts working, the problem is in the power circuit or control elements.

If the motor does not respond, it must be replaced. For FB15 fit original spare parts Nissan 27310-4M000 or analogues from Denso, Valeo.

How to check the fan speed resistor?

The resistor is located on the fan housing and has several terminals. Check it with a multimeter in resistance mode:

- Between pins 1 and 2: ~1 Ohm

- Between 1 and 3: ~2 Ohm

- Between 1 and 4: ~3 Ohms

If the values are very different, the resistor is faulty.

FAQ: Frequently asked questions about the heater fuse Nissan Sunny FB15

Is it possible to drive without a heater fuse?

No, it's dangerous! Without a fuse, the circuit remains unprotected, and if there is a short circuit, the wiring may catch fire. If a fuse blows too often, find the cause rather than operating the machine without it.

Why does the stove only work at speed 4?

This is a typical sign of a problem fan speed resistor. At maximum speed, the current bypasses the resistor, so it works. Replace the resistor (part Nissan 27315-4M000).

Where to buy a fuse for FB15?

Fuses of standard ratings (20A, 25A) are sold at any auto shop or AliExpress. For reliability, choose brands Bosch, Hella or Nissan Original. Cost - from 20 to 100 rubles per piece.

Can a blown fuse be repaired?

Technically, you can resolder a burnt-out thread, but this extremely dangerous. A homemade fuse will not trip if overloaded, which could result in a fire. Always use original fuses.

Why does the fuse only blow when the air conditioner is turned on?

In this case, the problem is most likely air conditioning compressor or its relay. When you turn on the A/C, the load on the circuit increases, and if there is a weak contact or short circuit somewhere, the fuse burns out. Check the A/C relay (usually labeled A/C RELAY).