PTC HEATER

Description and Operation

Description

The PTC (Positive Temperature Coefficient) heater is installed at the outlet or at the rear of the heater radiator. The PTC heater is an electric heater that uses a PTC element as an auxiliary heat source, supplementing the heat shortage of the diesel engine heat source. The electric heating system heats the cabin by heating the air directly from the heater. As the name implies, the resistance of the element is proportional to and sensitive to temperature changes.

Operating Principle: The ECM outputs a PTC ON signal and activates PTC relay 1. The heater controller controls PTC relay 2, and PTC relay 3 has a 15-second interval. However, PTC relay 3 can operate when battery voltage is above 12.4 V. The PTC heater operates under the following conditions:

• Battery voltage: 12.4 V or more
• Blower motor: operating
• Ambient and Coolant Temperature

Temperature TEMPERATURE	Coolant TEMPERATURE	PTC Operation
below -20°C (-4°F)	Below 75 °C	WE
10°C (50°F)	Below 65 °C	WE
12 °C or higher	-	OFF
-	80 °C or higher	OFF

Repair Procedures

Inspection

Functional Logic Check (manual only): Check PTC operation using the confirmation logic as shown below.

1. 1
   Input

   1. Set the floor mode to maximum heating.
   2. Turn off the blower.
   3. Press the intake (recirculation) button 5 times or more.
   4. The intake indicator and the climate button blink continuously at 0.5-second intervals.
   5. Confirm PTC operation by activating the blower switch.
   6. Each PTC relay activates at 3-second intervals.
   7. The logic test is automatically canceled after 30 seconds. It can also be canceled by the following:
      • Select the A/C or intake (recirculation) switch
      • Ignition switch OFF.
2. 2
   Cancel

   • Select the A/C or intake (recirculation) switch.
   • Turn the ignition switch to the OFF position.
   • The test is automatically cancelled after 30 seconds.
3. 3
   If the PTC function does not work, replace the PTC heater and check that it operates properly. If this does not solve the problem, replace the PTC heater.
4. 4
   Increase engine speed.
5. 5
   Check the current in the wiring using a multimeter with clamp probes.

   MODEL	Current (A)
   PTC 1 ON	0,1~33
   PTC 2 ON	0,1~33
   PTC 3 ON	0,1~33
   General	0,1~100

6. 6
   If the current is not within specification, check the wiring and connectors.
7. 7
   Turn the ignition switch to the OFF position.
8. 8
   Disconnect the PTC heater connector.
9. 9
   Measure the resistance between terminals 1, 2, and 3 of the PTC heater and ground.

   Resistance (0.3~1.5?

   

   1. PTC 1
   2. PTC 2
   3. PTC 3
10. 10
    If the measured resistance does not meet the specification, replace the PTC heater with a new one.

Functional Test: This test must be performed with the PTC heater on. Resistance Test

REPLACEMENT

1. 1
   Disconnect the negative (-) battery terminal.
2. 2
   Remove the floor console side cover [G] (A).

   

3. 3
   Disconnect the PTC heater connector (A).

   

4. 4
   Remove the PTC heater core (A) after loosening the fixing screws.

   

   

5. 5
   To install, perform the removal procedure in reverse order.