The core function of the wiper motor thermal protector is to prevent damage to the motor due to overheating or overcurrent. The thermal protector utilizes the physical characteristics of the bimetal to achieve intelligent protection by monitoring the dual parameters of temperature and current. Its design balances response speed, reset convenience and reliability, and it is a key component in ensuring the safe operation of automotive motors.
So, how to choose the right thermal protector to achieve the best protection effect? To match the right thermal protector, first of all, I have to understand the basic working principle of the wiper motor and why it needs thermal protection. When the wiper motor is working in the car, it may overheat for various reasons, such as motor blocking, overloading or long time use, and the role of the thermal protector is to prevent the motor from damaging or even causing fire.

1. The basic principle of thermal protector
Bimetal thermal protector (core element):
Material characteristics: made of two different coefficients of thermal expansion of the metal laminated, heat due to the expansion of the difference in bending.
Temperature Trigger: When the motor temperature exceeds the set threshold (e.g. 80°C~120°C), the bimetal sheet bends and deforms, pushing the contact to disconnect the circuit and force the motor to stop working.
Automatic reset: When the temperature drops, the bimetal restores its original shape and reconnects the circuit without manual intervention.

2. Current protection mechanism
Joule heat effect:
When the motor current is abnormally high due to blocking, overloading or short-circuiting, the current flowing through the bimetal will generate additional heat through Q=I²Rt (I is the current, R is the internal resistance of the protector).
The higher the current, the faster the heat generation: even if the ambient temperature is not exceeded, the excessive current will cause the bimetal to heat up quickly and trigger a disconnection.
Double protection logic:
Overload protection: for short-time high current (e.g. blocking current when the wipers are stuck by ice or snow).
Short-circuit protection: Prevents short-circuiting of the circuit resulting in a surge of current.

3. Synergy between temperature and current
Compound trigger conditions:
High Temperature + Normal Current: e.g. motor temperature rise due to long time continuous operation.
Normal temperature + overcurrent: e.g. instantaneous high current due to sudden blocking.
High temperature + overcurrent: the most dangerous situation, the protector will accelerate the response.

4. Typical application scenarios
Stuck wipers: motor stalls with a sudden increase in current and the protector cuts off the power supply within a few seconds.
Prolonged rainstorm mode: motor temperature rises due to continuous operation, the protector cuts off according to the temperature threshold.
Short circuit: Immediately triggers current protection to prevent the risk of fire.

5. Reset mechanism and safety
Automatic reset: Most of the wiper motors adopt resettable protectors, which automatically recover after cooling to avoid frequent replacement.

As the “invisible guardian” of automobile safety system, the thermal protector of wiper motor cuts off the source of danger at the critical moment through the double “sense of smell” of temperature and current. It not only avoids direct losses such as motor burnout and line meltdown, but also ensures the safety of driving vision in rainy days. With the development of automotive electrification, the design of such protectors is evolving towards higher precision and faster response, but its core mission remains the same: to guard complex mechanical life with simple physical principles.