Automotive Thermal Circuit Breakers Explained: Types, Benefits & Applications
In modern vehicles, reliable power protection is essential for safety and performance. Unlike traditional fuses, a thermal circuit breaker safeguards against overcurrent and can be reset and reused, making it a smarter and more cost-effective solution.
This guide explains what a thermal circuit breaker is, why vehicles need them, and the different KUOYUH product series that meet diverse automotive applications.
What is a Thermal Circuit Breaker?
A thermal circuit breaker is an electrical safety device that uses a bimetal strip, which bends when heated to interrupt excessive current flow.
- • How it works: When the current exceeds the rated value, heat causes the bimetal strip to bend, triggering the mechanism to open the circuit.
- • Advantage over fuses: Unlike fuses, which must be replaced once blown, thermal circuit breakers can be reset manually or automatically after the fault is cleared—making them reusable and cost-efficient.
In short: They protect wires and components while saving on maintenance.
Why Do Vehicles Need Thermal Circuit Breakers?
- • Overcurrent Protection: Prevents damage to wiring and sensitive electronics.
- • Resettable Design: No need to carry spare fuses—just reset the breaker.
- • Lower Maintenance Costs: Reduces downtime, especially valuable for fleets and commercial vehicles.
- • Enhanced Safety: Minimizes fire hazards, overheating, and electronic module failures.
This is why more cars, trucks, buses, RVs, and modified vehicles are switching to resettable circuit breakers instead of single-use fuses.
Types of KUOYUH Thermal Circuit Breakers
According to SAE J553 automotive standards, KUOYUH thermal circuit breakers are available in four main types:
Type I — Auto Reset (KUOYUH AR Series)
Operation: Trips when overloaded, then automatically resets after cooling, until the fault is removed.
Feature: Suitable for temporary overloads; no manual intervention required.
Typical Applications:
- • Lighting and auxiliary systems: interior lights, reading lamps, trunk lights.
- • Convenience functions: power windows, electric mirrors, low-power seats.
- • Small motor drives: wiper motor, auxiliary cooling fan, door lock actuator.
- • Auxiliary power circuits: 12V car chargers, small retrofit lighting.
Ideal for temporary current surges, but not recommended for continuous overload circuits.
KUOYUH Product: AR Series circuit breaker
Type II — Modified Reset (KUOYUH 102 Series)
Operation: Non-cycling. Remains open after tripping and requires the power to be removed to reset.
Feature: Prevents devices from automatically restarting, ensuring troubleshooting before restoration.
Typical Applications:
- • Engine & power systems: fuel pump, electric cooling fan, ignition systems.
- • Safety systems: EPS power steering, ABS, airbag modules.
- • Comfort equipment: power seats, sunroof, power tailgate.
- • Commercial vehicles: bus & truck lighting, HVAC circuits
Especially suitable for critical circuits that require inspection before restart, reducing risks of fire or secondary damage.
KUOYUH Product: 102 Series circuit breaker
Type III — Manual Reset (KUOYUH 103 Series)
Operation: Non-cycling. Remains open after tripping and requires a manual push-button or lever reset.
Feature: Safest design, as human confirmation is required before restoring the circuit.
Typical Applications:
- • Long-haul vehicles: bus & truck power windows, HVAC systems, refrigeration units, auxiliary circuits
- • Off-road & RVs: onboard refrigerators, lighting, charging systems.
- • Passenger cars: seat heaters, infotainment, power tailgate
- • Aftermarket & retrofit: dash cameras, audio amplifiers, auxiliary circuits.
Best suited for safety-critical or high-value equipment where manual inspection is required.
KUOYUH Product: 103 Series circuit breaker
Type III* — Manual Reset + Switch (KUOYUH 16 Series)
Operation: Same as Type III but with a switching function, allowing users to disconnect or reconnect power manually.
Feature: Dual function — both a circuit breaker and a power switch.
Typical Applications:
- • Auxiliary circuits: additional lighting, onboard refrigerators, camping appliances
- • Aftermarket accessories: dash cameras, audio amplifiers, LED light bars
- • Commercial & specialty vehicles: HVAC systems, add-on electrical circuits.
- • Off-road & RVs: onboard water pumps, air compressors, electric winches
Perfect for camping, modification, and commercial vehicles, offering protection and control.
KUOYUH Product: 16 Series circuit breaker
Comparison Table
| SAE Type | Features | Typical Automotive Applications |
| Type I (Auto Reset) | Trips when overloaded, auto resets after cooling; cycles until fault cleared | Wiper motors, headlights, cooling fans, horns |
| Type II (Modified Reset) | Stays open after trip; requires power-off to reset; prevents immediate restart | Power windows, power seats, sunroof, door locks |
| Type III (Manual Reset) | Stays open after trip; requires manual reset by button/lever | Main power circuits, power distribution units, trailer modules, high-power motors |
| Type III* (Manual Reset + Switch) | Same as Type III, but also functions as a switch | Battery disconnect, RV power control, service vehicles, modified car power switch |
Why Choose KUOYUH?
A thermal circuit breaker is an electrical safety device that uses a bimetal strip, which bends when heated to interrupt excessive current flow.
- • Certified to SAE international standards
- • Complete product range: AR, 102, 103, and 16 Series.
- • Broad applications: automotive, RV, marine, industrial equipment, outdoor systems.
Contact KUOYUH today to discover the most reliable circuit protection solutions for your vehicles and equipment!
