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Heating, Ventilation, and Air Conditioning

PTC Heater (Diesel Engine) Description and Operation

In this manual: Heating, Ventilation, and Air Conditioning
General Information — 15Maintenance — 7Engine Mechanical System — 84Engine Electrical System — 49Emission Control System — 22Fuel System — 95Clutch System — 28Manual Transmission — 21Dual Clutch Transmission (DCT) System — 47Drive Shaft and Axle — 20Suspension System — 36Steering — 23Restraints — 39Brake System — 54Body (Interior and Exterior) — 209Body Electrical System — 254Heating, Ventilation, and Air Conditioning — 56
~1min read

Description

The PTC (Positive Temperature Coefficient) heater is installed at the outlet or rear side of the heater core. The PTC heater is an electric auxiliary heater that compensates for the lack of internal heat source in high-efficiency diesel engines. The electric heater warms the cabin by directly heating the air passing through it. The name implies that the element has a proportional change in resistance that is sensitive to temperature.
Operating principle: The ECM outputs a PTC ON signal and turns on PTC relay 1. The heater controller then turns on PTC relay 2 and PTC relay 3 at 15-second intervals. However, PTC relay 3 may operate only when battery voltage is above 12.4 V. Operating condition: The PTC heater operates under the following conditions:
  • Battery voltage: 12.4 V or higher
  • Engine is running
  • Ambient Temperature and Coolant Temperature
Ambient
Temperature		 Coolant
Temperature		 PTC
Operation
Below -20°C
(-4°F)		 Below 75 °C ON
10°C (50°F) Below 65 °C ON
12 °C or higher - OFF
- 80 °C or higher OFF

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