Town & Country V6-3.3L VIN R (2003)
requires to activate its Cabin Heater Assist Control Output. This output is a low side driver (coming from FCM pin 15) which supplies a ground signal
to the Cabin Heater (pin 5). When the Cabin Heater receives this ground signal input, it interprets this as an activation signal. The FCM low side
driver is also capable of diagnostic sensing. The driver will sense an open circuit when the driver is off, and will sense a short to voltage when the
driver is on. The FCM will set DTCs for both of these types of faults.
For vehicle's with a Manual Temperature Control system, the DCHA will activate only:
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when the engine is running.
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when the coolant temperature is below 66 °C (151 °F).
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when the fuel tank has greater than 1/8 of a tank of fuel.
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when the Power switch on the A/C - Heater Control Module is on.
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when the Blend control on the A/C - Heater Control Module is set above 90% reheat (within 2 detents of the full heat position).
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once per ignition cycle, when the ambient temperature is below 9 °C (49 °F), and the vehicle speed is above 25 km/h (15.5 mph) for two minutes
, and the Blend control on the A/C - Heater Control Module is set anywhere from 80% to 90% reheat (3 to 4 detents from the full heat position).
Under this circumstance, the DCHA will remain active for five minutes unless additional input is supplied to the DCHA.
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when the Front Control Module (FCM) sees the Cabin Heater Activation request that is bussed from the A/C - Heater Control Module.
For vehicles with a Automatic Temperature Control system, the DCHA will activate only when the:
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VIN indicates that the vehicle has a diesel engine
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vehicle's odometer reads more than 5 miles.
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engine speed is above 500 rpm.
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coolant temperature is below 66 °C (151 °F).
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fuel tank has greater than 1/8 of a tank of fuel.
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Power switch on the Automatic Temperature Control is on.
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Driver Temperature Control on the Automatic Temperature Control is set above 22 °C (72 °F).
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Front Control Module (FCM) sees the Cabin Heater Activation request that is bussed from the Automatic Temperature Control.
When the DCHA starting sequence begins, the glow plug and the combustion air fan are activated.
After 30 seconds, the fuel dosing pump begins operating and the combustion air fan operation is suspended for 3 seconds. Subsequently, the
combustion air fan speed is increased in two ramps within 56 seconds to nearly full load operation. After a stabilization phase of 15 seconds, the
combustion air fan speed is again increased in a ramp within 50 seconds to nearly full load. After reaching full load fuel delivery, the glow plug is
deactivated and the combustion air fan operation is increased to full load. During the subsequent 45 seconds, as well as in normal operation, the glow
plug functions as a flame sensor to monitor the flame condition. After all these events, the automatically controlled heating operation starts.
In case of a no flame or a flame out condition, a restart is automatically initiated. If the no flame condition persists, fuel delivery is stopped and the
heater enters an error lockout mode with a rundown of the combustion air fan. This will set one or more DTCs in the DCHA Control's memory. If six
continuous attempts to start the heater fail due to one or more faults in the DCHA system, the heater enters a heater lockout mode. This will set DTC
B1813 along with any other fault(s) that the DCHA Control identified.
Heating
During the automatically controlled heating operation, when the coolant temperature reaches 76 °C (169 °F), the heater will switch to a part load
operation. When the coolant temperature reaches 83 °C (181 °F) or if the heater runs for longer than 76 minutes the heater will switch to a control
idle period. If the coolant temperature drops to 73 °C (163 °F) during a control idle period, the heater will perform a regular starting sequence into full
load operation. A drop in coolant temperature to 66 °C (151 °F) during part load operation will cause the heater to switch to a full load operation.
Deactivation
For vehicles with a Manual Temperature Control system, the DCHA will deactivate if the:
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engine is turned off.
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coolant temperature reaches 83 °C (181 °F).
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heater runs longer than 76 minutes (for normal automatic controlled heating operation).
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heater reaches 5-minute timeout period (for once per ignition cycle operation).
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fuel tank has less than 1/8 of a tank of fuel.
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Power switch on the A/C - Heater Control Module is off.
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Blend Control on the A/C - Heater Control Module is set below 75% reheat. 5 detents
For vehicles with a Automatic Temperature Control system, the DCHA will deactivate if the:
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engine speed drops below 500 rpm.
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engine is turned off
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coolant temperature reaches 83 °C (181 °F).
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heater runs longer than 76 minutes.
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fuel tank has less than 1/8 of a tank of fuel.
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Power switch on the Automatic Temperature Control is off.
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Comfort level is attained as determined by the temperature setting on the Automatic Temperature Control.
When the heater is deactivated, the combustion stops and a run-down sequence begins. During the run-down sequence, the combustion air fan
continues operation to cool down the heater. The fan is automatically switched off after the run-down sequence is complete. The run-down time and
