Find the radiator fan switch for your vehicle

Fan switch for cars: find out more! How to choose, when to change , and how much they cost

Blower sensors and switches are electronic devices which provide stable operation of the air conditioning system. According to designation they may perform different functions: change working liquid temperature, regulate blower operation, control time of its turning on and off.

Types of blower sensors and switches

According to operating principle there are the following types of sensors:

• sensors with negative temperature coefficient;
• sensors with positive temperature coefficient.

By operating principle relays are divided into:

• electromagnetic;
• thermorelays (thermoswitches).

Construction of blower sensors and switches

Blower control unit is a microprocessor with software and microcircuit with contacts, mounted in a single housing. Special varnish coating is used for protection of contacts and conducting paths from exposure to soiling and moisture. Control unit reads signals of temperature sensors, selects optimal moment for blower turning on and sends corresponding electric signal to relay contacts. At current supply to relay winding its core moves and closes open contacts, which actuate blower electromotor.

Semiconductor devices, which change resistance according to temperature – thermoresistors - are used as sensors for cooling liquid or engine compartment temperature. Usually, temperature sensors have threaded connection and are installed in pipe of engine block. There are several such sensors in most modern cars. There are sensors with integrated microprocessor, which is responsible for activation of signal indicator when temperature of the cooling liquid reaches its critical value.

Thermoswitches with normally opened contacts may be used instead of switches in some cars. Basically, bimetallic plate and push-rod are mounted into the thermoswitch construction. When cooling liquid heats up to specific temperature, the plate deforms and affects the push-rod. The latter closes contacts while moving, so the blower turning on is performed. Thus, at lowering of cooling liquid temperature the blower turns off. Temperature of the thermoswitch activation may differ according to car brand.

Operation of the blower sensors and switches

Components have no strict lifetime limits. They will serve for long, if you follow manufacturer's recommendations on operation of the vehicle and its systems, follow installation rules and buy parts made only of high-quality materials. Parts are sensitive to high temperature exposure, which should be taken into account, if the car is operated in hot climate conditions.

Defects of the blower sensors and switches

• housing cracking;
• contacts oxidation;
• wires breakage;
• fastenings damaging;
• soiling of component elements;
• short circuit;
• microprocessor burning;
• plastic elements melting.

Signs of the blower sensors and switches defects

• constant operation of the blower with engine running;
• absence of blower reaction to engine temperature increasing or air-conditioner turning on;
• fuel consumption increase;
• car handling worsening;
• lowering of air-conditioner operation efficiency.

Causes of the blower sensors and switches defects

• exposure of parts to moisture;
• operation of vehicle in off-road conditions;
• instability of current in mains;
• low quality of components;
• improper installation;
• housing pressurization failure;
• frequent engine overheating.

Replacement of the blower sensors and switches

Usually, blower sensors, relays and switches are not repaired. If a defect appeared it is more practical to buy and install a new part. Replacement can be easily performed by your own efforts. But in order to define actions order you need to specify part location (in different car models, the same sensors may be located in different places). To do so use instructions, given in your vehicle technical documentation.

Probably you will need to flush down cooling liquid during replacement of the temperature sensors and thermoswitches. This process is quite lengthy, so if you don't have time, it is better to apply to specialists for help.

If you decided to install a new sensor by yourself, use the next instruction:

1. Disconnect the negative wire from the battery.
2. Gain access to the part mounting location. Probably you will need to remove the air filter and the radiator.
3. Flush down cooling liquid into a reservoir, prepared in advance.
4. Unscrew the defective sensor, install a new one to its place.
5. Perform installation of removed components in the reversed order.

AutoDoc professional assistance

Operative blower sensors and switches are guarantee of safe and comfort driving. If one of these components is broken, you should not postpone its replacement – this can cause blower failure and engine breakdown. You can always buy blower sensors and switches in our online-shop. We guarantee excellent quality of production, quick delivery and always ready to provide qualified help of our specialists.