Diagnosing cooling loop faults
Reading symptoms back to the failed component.
You'll learn
- Explain diagnosing cooling loop faults at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real vehicle
Overview
Coolant loop faults rarely announce themselves directly — they show up as power limits, slow charging or an unexplained fan running constantly.
In depth
Fault diagnosis
Diagnose the cooling fault
Work through the clues to find the failed component.
Charging power capped low on a warm day
A car accepts only 40 kW at a 150 kW charger despite a healthy battery and moderate ambient temperature.
Diagnostic checks
Your diagnosis
| Symptom | Likely cause |
|---|---|
| Fan runs constantly, coolant stays hot | Low refrigerant charge or blocked radiator |
| Charging power drops mid-session | Chiller reaching its capacity limit |
| Coolant level warning | Leak somewhere in the loop |
| Pump audible but no flow effect | Airlock or failed impeller |
Key takeaways
Remember this
- Cooling faults usually appear as power limits, not direct warnings.
- Cross-reference coolant temperature, fan behaviour and refrigerant pressure to localise a fault.
- A stuck-high coolant temperature with low refrigerant pressure points at the chiller.
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