Heat blasts even when set cold
Vents blow hot air no matter what you set on the climate control panel.
Pushbutton ACC controls the heater monovalve and blend flaps via vacuum. A failed monovalve passes hot coolant to the heater core full-time.
What the diagnosis checks
- Pinch the heater hose to the firewall — does the air get cooler?
- Does the climate control panel push-buttons illuminate when pressed?
Possible causes it points to
- Failed monovalve (heater control valve)
- ACC head unit PCB
- ACC head fuse / power
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