Air conditioning system in a car Nissan Almera is a complex mechanism where each component plays a critical role in providing comfort. One of the most important components responsible for starting cooling is the electromagnetic relay that controls the operation of the compressor. It is this small element that often causes the fan to blow warm air, despite a working engine and the presence of freon.
Owners of sedans and hatchbacks Nissan Almera G15 generations often encounter a situation where the air conditioner stops turning on after the engine is stopped or when there is a high load on the on-board network. In most cases, the problem lies not in the most expensive compressor itself, but in the control relay, which can oxidize, overheat, or simply fail due to voltage surges. Understanding the principle of operation and the ability to quickly diagnose this malfunction will save you a significant amount of money and time searching for a repairman.
Ignoring signs of malfunction can lead to more serious damage, since incorrect operation of the relay sometimes causes sticking of the contacts, which in turn leads to continuous operation of the compressor and its rapid wear. Therefore, at the first symptoms of a malfunction in the climate system, it is necessary to conduct a thorough check of the electrical control circuit.
Operating principle and purpose of relays in the air conditioning system
Electromagnetic relay in a car Nissan Almera acts as a powerful switch that connects the battery to the compressor solenoid winding. The compressor consumes quite a lot of current, and if it were controlled directly through the climate control unit or a button on the instrument panel, the contacts of these elements would quickly burn out. The relay takes on the load, closing a powerful circuit only when it receives a weak control signal.
The startup process occurs as follows: when you activate the air conditioner with the button AC, the control unit sends a signal to the relay coil. Under the influence of a magnetic field, the armature is attracted and closes the power contacts, supplying a voltage of 12 volts to the compressor clutch. If the voltage on the coil disappears or is insufficient, the contacts open and the compressor stops.
It is important to understand that the relay does not operate in isolation. It is in conjunction with freon pressure sensors and evaporator temperature sensors. Control unit Nissan Almera checks the pressure in the system before sending a signal to the relay. If there is little freon or the pressure is too high, the signal to turn on will simply not be received in order to protect the compressor from damage.
The main reasons for relay failure on Nissan Almera
The most common cause of failure is overheating of the contacts due to high current consumption. Over time, the metal of the contacts oxidizes, which increases resistance and causes even more heat, leading to deformation or complete sticking. In the Russian climate with its temperature changes and high humidity, this process accelerates, especially if the relay is located in the engine compartment without reliable protection.
Another common problem is wear of the armature spring or loosening of the coil mount. Vibrations that are inevitable during engine operation can, over time, cause the armature to no longer fit tightly to the core, causing a characteristic crackling sound or a complete lack of operation. In addition, factory defects in the insulation of the coil winding can lead to an inter-turn short circuit, due to which the relay no longer generates a sufficient magnetic field.
- 🔥 Oxidation of power contacts under the influence of moisture and heat
- ⚡ Short circuit of the control coil winding due to insulation aging
- 🛠 Mechanical wear of moving parts inside the plastic case
- 🔋 Voltage surges in the vehicle’s on-board network caused by a faulty generator
Fault diagnosis: step-by-step instructions
The first diagnostic step is to visually inspect the fuse and relay box located in the engine compartment. You need to find the relay responsible for the air conditioner, it is usually marked COMP or A/C. The relay body often has a diagram showing the pin locations, making the testing process easier. If you see traces of plastic melting or a characteristic burning smell, the problem is clearly in this unit.
For a more accurate check, use a multimeter. First, check the presence of power at the power contact of the relay with the ignition off - there should be constant voltage from the battery there. Then, with the engine running and the air conditioning activated, check for the presence of a control signal at the control contacts. If there is power, but the relay does not click, the problem is in the coil or the control unit itself.
The easiest way to check is to replace the relay with a known good one. Take a relay with similar markings (for example, from the headlight or power window circuit, if their parameters are the same) and install it in place of the suspicious one. If the air conditioner started working, then the problem was in the relay. This eliminates the need for complex chain testing during service.
⚠️ Attention: When testing a circuit with a multimeter, be extremely careful. Do not touch the metal probes of two terminals with different potentials at the same time to avoid a short circuit that could burn fuses or the engine control unit.
- Air conditioner doesn't turn on at all
- The air conditioner operates intermittently
- A clicking sound is heard, but the compressor does not spin
- The compressor runs constantly without shutting down
☑️ Preparation for relay diagnostics
Connection diagram and pinout
Understanding relay pinouts is critical for proper diagnosis and replacement. In standard relays Nissan Almera Usually 4 or 5 pins are used. The main power contacts (85 and 86) are responsible for supplying voltage to the coil, and the power contacts (30 and 87) are responsible for supplying current to the load. Some modifications have an additional contact 87a for a normally closed circuit.
The relay body is usually marked with a diagram, but if it is erased, you can use the universal correspondence table. It is important not to confuse the control circuit with the power circuit, since connecting the multimeter to the power circuit without a load can give false readings or damage the device.
| Contact number | Purpose | Circuit Description | Signal type |
|---|---|---|---|
| 30 | Power input | Connects directly to the battery positive via a fuse | Constant +12V |
| 87 | Output to load | Goes to the winding of the compressor electromagnet | Trigger power |
| 85 | Control (weight) | Connects to the control unit via sensors | Control signal |
| 86 | Management (+) | Connects to positive via fuse | Constant +12V |
Features of relays in different generations of Almera
In the G15 generation (2012-2020), the relay is often integrated into the fuse box under the hood, whereas in older models it can be located separately in the cabin or under the dashboard. It is important to consider the location when troubleshooting.
DIY relay replacement process
Replacing the air conditioning compressor relay is a procedure that is accessible even to a beginner and does not require special equipment. First you need to de-energize the system by disconnecting the negative terminal of the battery. This will prevent accidental shorting when removing the element from the block. Next, find the relay box in the engine compartment, it is usually located in a plastic case with a cover.
Gently press the unit cover latches and remove it. Find the required relay using the markings on the cover or in the service documentation. The relay is usually inserted into the block without bolts; you just need to pull it up with a little force. Be careful not to damage the plastic pad latches.
Install the new relay, making sure that the contacts match the pins in the block. Do not use excessive force when installing. After installation, connect the battery, start the engine and check the operation of the air conditioner. If everything is done correctly, you will hear the characteristic click of the relay and feel cold air through the vents.
- 🔧 Use only original relays or high-quality analogues with similar parameters
- 🚫 Do not try to “bend” the contacts in the block; if they are loose, replace the entire block
- 🧹 Before installing a new relay, clean the contacts in the block from oxides and dirt
If you cannot find a relay by marking, look at its rated current (usually 20-30A) and voltage (12V) on the case to find an analogue in an auto parts store.
Selection of high-quality analogue and original spare parts
When choosing a replacement, it is important to understand that cheap analogues may not last long. Original relay Nissan Almera made of materials resistant to high temperatures and vibrations, which is critical for the engine compartment. The body of the original part always has the manufacturer’s logo and exact markings corresponding to the catalog number.
If you decide to use an analogue, pay attention to brands such as Denso, Toyota (as compatible components are often used) or specialized electronics manufacturers. The main thing is to check the rated current and contact diagram. An incorrectly selected relay may not operate when starting the compressor or, conversely, may not turn off, which will lead to overheating.
⚠️ Attention: Using a relay with an increased operating current is not always a solution to the problem. This may result in the control signal from the control unit being insufficient to operate, and the air conditioner will not turn on.
The original relay ensures stable operation of the air conditioning system throughout its entire service life, while cheap analogues often require repeated replacement after a few months.
Possible problems after replacing the relay
Sometimes after replacing the relay the problem does not go away, which may indicate deeper problems in the system. If the air conditioner does not turn on, check the fuse, which often blows along with the relay due to a short circuit. It is also worth checking the condition of the wiring leading to the compressor, as the insulation may be damaged, causing current leakage.
Another reason could be a malfunction of the compressor itself or low freon levels. If there is no pressure in the system, the pressure sensor will not give a command to turn on the relay, even if it is working properly. In this case, the air conditioner will only work until the pressure drops below a critical level, or will not turn on at all.
Also pay attention to the freon pressure sensor. If it gives incorrect readings, the control unit may block the signal from the relay. For accurate diagnostics, it is necessary to connect a pressure gauge station and check the pressure in the system, as well as scan the car for errors in the climate control unit.
⚠️ Attention: If after replacing the relay the air conditioner turns on but immediately turns off, this almost certainly indicates a low refrigerant level or a faulty pressure sensor, rather than an electrical problem.
Features of the pressure sensor
The freon pressure sensor has three contacts and transmits a signal to the control unit in the form of alternating voltage. In the absence of freon, the voltage will be zero or maximum, which blocks the operation of the compressor.
If replacing the relay does not solve the problem, do not look for other electrical problems until you check the freon level and the operation of the pressure sensor, as these are the most likely causes of the starting block.
FAQ: Frequently asked questions
How to determine that it is the relay that is faulty and not the compressor?
The easiest way is to replace the relay with a known good one. You can also listen to a characteristic click when you turn on the air conditioner: if there is a click, but the compressor does not spin, the problem may be in the clutch or the relay itself. If there is no click, check the power to the relay.
Is it possible to drive with a faulty air conditioning relay?
You can drive, as this does not affect the movement of the car, but the air conditioning will not work. However, if the relay is stuck in the closed position, the compressor will run constantly, which can lead to overheating and failure, as well as draining the battery.
Where is the compressor relay located on Nissan Almera G15?
On most models Nissan Almera The G15 relay is located in the main fuse box in the engine compartment. This is usually a black block with a cover located to the right of the battery. There is a diagram on the cover showing the location of the air conditioning relay.
How much current does the compressor relay consume?
The compressor current rating is usually around 20-30 Amps, so the relay should be rated at a minimum of 30A. Using a relay with a lower current will lead to rapid overheating and failure.
Why does the air conditioner run jerkily?
Jerky operation of the air conditioner is often caused by oxidation of the contacts inside the relay, causing the connection to become unstable. This may also be a sign of low freon levels when the pressure fluctuates and the sensor constantly turns the compressor on and off.