Dodge Nitro. Manual - part 780

 

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Dodge Nitro. Manual - part 780

 

 

Courtesy of CHRYSLER LLC 

An electric positive temperature coefficient (PTC) heater unit (1) is used on vehicles when equipped with the 
2.8L diesel engine. The PTC heater unit aids in passenger compartment heating by compensating for the lower 
engine coolant temperatures produced by the diesel engine. The PTC heater unit is mounted in the HVAC air 
distribution housing, downstream of the heater core and is controlled by the diesel engine control module 
(ECM) and the totally integrated power module (TIPM) through two relays in diesel accessory fuse/relay block 
located below the left front fender. 

The PTC heater consists of a molded plastic mounting plate (2) with an integral wire connector receptacle (3). 
Concealed behind the mounting plate are four heating elements with fins (4) that transfer the heat produced by 
the PTC heater to the conditioned air flowing within the air distribution housing. A positioning tab (5) is 
molded onto the end of the heater unit to help support the heater unit inside the air distribution housing. The 
PTC heater unit is connected to the vehicle electrical system through the instrument panel wire harness. 

The PTC heater unit is accessed for service from underneath the instrument panel. 

OPERATION 

HEATER UNIT 

The positive temperature coefficient (PTC) heater unit dissipates 1 kW of electrical power through 4 heating 
bars. The totally integrated power module (TIPM) operates the two relays for the PTC heater unit. The PTC 
heater unit is split into two "banks". Each bank is driven separately based on alternator load. This allows for 
lower in-rush current and optimum battery charging. After a bank has been turned on, another bank can only be 
turned on 10 seconds after the previous. On average, the PTC banks are not switched more than 25 times for 
each vehicle start. Electrical power output is between 900-1050 W. 

The control system for the PTC heater unit is diagnosed using a scan tool. Prior to replacing a PTC heater unit, 
check for any diagnostic trouble codes (DTCs) related to the ECM, TIPM and heating-A/C system (refer to 
HEATING & AIR CONDITIONING - ELECTRICAL DIAGNOSTICS for more information). 

The PTC heater unit cannot be adjusted or repaired and, if faulty or damaged it must be replaced. 

DIAGNOSIS AND TESTING 

HEATER UNIT 

NOTE:

LHD model shown. RHD model similar.

WARNING:

Disable the airbag system before attempting any steering wheel, steering 
column, or instrument panel component diagnosis or service. Disconnect 
and isolate the negative battery (ground) cable, then wait two minutes for 
the airbag system capacitor to discharge before performing further 
diagnosis or service. This is the only sure way to disable the airbag 
system. Failure to take the proper precautions could result in accidental 
airbag deployment and possible serious or fatal injury.

 

2007 Dodge Nitro R/T 

2007 HVAC Heating & Air Conditioning - Service Information - Nitro

  

Prior to replacing the positive temperature coefficient (PTC) heater unit, check for any diagnostic trouble codes 
(DTCs) related to the engine control module (ECM), totally integrated power module (TIPM) and the heating-
A/C system and repair as necessary (refer to HEATING & AIR CONDITIONING - ELECTRICAL 
DIAGNOSTICS for more information). 

1. Disconnect and isolate the negative battery cable.  

2. Disconnect the wire harness connector from the PTC heater unit. See REMOVAL.  

3. Using an ohmmeter, check for continuity between all of the PTC heater unit terminals. In each case there 

should be continuity. If OK, repair the wire harness circuits between the PTC heater unit and the TIPM. If 
NOT OK, replace the PTC heater unit.  

REMOVAL 

HEATER UNIT 

NOTE:

For circuit descriptions and diagrams, refer to the appropriate wiring 
information. The wiring information includes wiring diagrams, proper wire and 
connector repair procedures, further details on wire harness routing and 
retention, as well as pin-out and location views for the various wire harness 
connectors, splices and grounds.

WARNING:

Disable the airbag system before attempting any steering wheel, steering 
column, or instrument panel component diagnosis or service. Disconnect 
and isolate the negative battery (ground) cable, then wait two minutes for 
the airbag system capacitor to discharge before performing further 
diagnosis or service. This is the only sure way to disable the airbag 
system. Failure to take the proper precautions could result in accidental 
airbag deployment and possible personal injury or death.

NOTE:

LHD model shown in illustrations. RHD model similar.

 

2007 Dodge Nitro R/T 

2007 HVAC Heating & Air Conditioning - Service Information - Nitro

  

Fig. 207: HVAC Housing Assembly 
Courtesy of CHRYSLER LLC 

1. Disconnect and isolate the negative battery cable.  

2. If equipped, remove the silencer from below the driver side of the instrument panel. Refer to 

REMOVAL .  

3. Disconnect the wire harness connector from the mode door actuator (2) and the blend door actuator (6) 

located on the driver side of the air distribution housing. See REMOVAL for more information.  

4. Carefully disengage the retaining tabs (3) that secure the mode door actuator and the blend door actuator 

to the actuator mounting bracket (5) and remove the actuators.  

5. Remove the three screws (1) that secure the actuator mounting bracket to the air distribution housing and 

remove the bracket.  

6. Remove the screw (8) that secures the driver side front floor duct (7) to the air distribution housing and 

remove the duct 

Fig. 208: Wire Harness Connector, Wire Connector Lock & Positive Temperature Coefficient 
(PTC) Heater Unit 
Courtesy of CHRYSLER LLC 

7. Disengage the wire connector lock (2) that secures the wire harness connector (1) to the positive 

temperature coefficient (PTC) heater unit (3) and disconnect the connector from the heater. 

NOTE:

PTC heater shown removed from distribution housing for clarity.

NOTE:

To disconnect the wire harness connector from the PTC heater, disengage 
the connector lock while pulling the connector away from the heater unit.

 

2007 Dodge Nitro R/T 

2007 HVAC Heating & Air Conditioning - Service Information - Nitro

  

Fig. 209: Removing/Installing Screws That Secure PTC Heater Unit To Air Distribution Housing 
Courtesy of CHRYSLER LLC 

8. Remove the two screws (1) that secure the PTC heater unit (2) to the air distribution housing (3).  

9. Carefully pull the PTC heater unit straight out of the air distribution housing.  

INSTALLATION 

HEATER UNIT 

Fig. 210: Removing/Installing Screws That Secure PTC Heater Unit To Air Distribution Housing 
Courtesy of CHRYSLER LLC 

1. Carefully install the positive temperature coefficient (PTC) heater unit (2) into the driver side of the air 

distribution housing (3). Make sure to position the two locator tabs on the end of the heater unit into the 
molded locator indentations on the right side of the air distribution housing.  

NOTE:

LHD model shown. RHD model similar.

 

2007 Dodge Nitro R/T 

2007 HVAC Heating & Air Conditioning - Service Information - Nitro

  

 

 

 

 

 

 

 

Content   ..  778  779  780  781   ..