PT Cruiser L4-2.4L Turbo VIN G (2004)
Auxiliary Cabin Heater: Description and Operation
Vehicles equipped with the diesel engine are also equipped with a supplemental cabin heater system. In this system, a coolant heater is used to preheat
the engine coolant to aid in cabin heating. Engine coolant is preheated using resistance heating. Current from the alternator is supplied to the three glow
plug type heating elements which reside in a single heater housing in the stream of engine coolant. As the coolant is routed from the engine, it passes
over the ends of the glow plugs, the heat is transferred to the coolant and then to the heater core. This provides additional heat to the passenger
compartment. The supplemental cabin heater system is interfaced to the vehicles on-board computer systems and DRBIII(R) diagnostics.
With the ignition turned to the On position, three temperature sensors record the ambient air in order to determine if it is cold enough to turn on the
supplemental engine coolant heater. One sensor is in the vehicle on the battery, under the driver's seat. The other two sensors are in the engine
compartment (inlet air temperature and manifold temperature). Based in the lowest temperature of the three temperature sensors, a pre-determined
coolant temperature set point is established at which the engine coolant heaters will shut off.
For example, if the lowest recorded temperature from the three sensors is 0° C (32° F) or below, the heaters will shut off when the coolant temperature
reaches 75° C (167° F). If the lowest ambient air temperature at key on is 10° C (50° F) or higher, then the heaters will not turn on
There are three heating elements in the assembly:
Plug 1 = 300 W, Plug 2 = 400 W and Plug 3 = 300 W. Plug 1 is tied to one relay, while plugs 2 and 3 are tied to a second relay. Because there are 3
plugs with only 2 relays, when the auxiliary diesel engine coolant heater is enabled by the engine controller, the firing sequence is as follows:
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a.Plug 1 only.
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b.Plugs 2 and 3 only.
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c.Plugs 1 to 3.
At each step, the powertrain control module (PCM) monitors loads on the alternator to see if it is OK to proceed to the next phase of the firing sequence.
The system will back out in the reverse order when a problem is encountered.
