0000-00
(13) PTC heater control
A. Overview
The supplementary electrical heater is installed in DI engine equipped vehicle as a basic equipment. The
PTC system is operated according to two temperature values measured at the coolant temperature
sensor and HFM sensor. This device is mounted in the heater air outlet and increase the temperature of
air to the passenger compartment. Because PTC system is heated by electrical power, high capacity
alternator is required. PTC does not operate during engine cranking, while the battery voltage is lower
than 11 V or during preheating process of glow plugs.
B. Components
HFM (intake air
temperature)
Coolant temperature
sensorPTC heaterD20DTR ECU
PTC 1 relay
PTC 2 relay
PTC 3 relay
PTC Fuse 3 (40A)PTC Fuse 2 (40A)PTC Fuse 1(40A)
Relay box in engine compartment
C. Operation process
The ceramic PTC has a feature that the resistance goes up very high at a certain temperature. There
are three circuits in PTC heater. Only one circuit is connected when PTC1 relay is ON, and two circuits
are connected when PTC2 relay is ON.
