Theory and operation
One vehicle may have several coolant loops that combine or separate by operating mode; the refrigerant circuit may heat or cool both cabin and battery.
Thermal Systems / Diagnostic guide
EV THERMAL-SYSTEM MAP.
Trace battery, motor, inverter, charger and cabin heat through pumps, valves, chillers and heat exchangers.
EV GUIDE17/24
Use this guide to organize evidence. Vehicle-specific high-voltage access, measurements and component isolation require OEM procedures, appropriate qualifications, rated PPE and approved test equipment.
GUIDE PURPOSE
Diagnose the system—not one isolated value.
Confirm vehicle state, operating conditions and the full DTC record before clearing evidence or opening the high-voltage system.
Diagnostic evidence
Map every pump, valve, temperature sensor, chiller, radiator, heater and refrigerant heat exchanger before interpreting temperature differences.
Safe diagnostic path
Use commanded positions and measured temperature change to prove heat movement, not merely actuator noise.
Boundary and common error
Do not open coolant or refrigerant circuits without the specified HV disable, recovery and filling procedures.
Specifications, connector access, disable sequences, wait times and allowable tests vary by model and voltage architecture.