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| Illustration 1 | g01121128 |
Block diagram of the right extender burner cdontrol circuit. | |
In order to control the right extender burner, the ECM monitors the status of the burner system switch, the right extender mode switch, the right extender temperature switch, the right extender flame sensor, the burner identification harness code plug and the key switch. The ECM determines the status of the burner and then determines which outputs to activate or deactivate in order to reach the selected burner status. If the burner system switch is in the OFF position or in the SPRAY position, the ECM will not attempt to ignite the burner or will turn the burner OFF if already ignited. With the burner system switch in the BURNER position, the ECM will operate the right extender burner in one of three modes depending on the position of the right extender mode switch.
AUTO Mode - Normal Operation
During normal operation the mode switch should be in the AUTO position. The ECM will check the status of the key switch input in order to determine if the machine is ON. If the key switch is ON, the ECM monitors the temperature switch in order to determine the temperature of the burner. If the temperature switch is closed (cold), the ECM will initiate the burner ignite cycle. The ignite cycle consists of the following sequence of steps:
- The right extender blower is operated at HI speed for 15 seconds in order to purge gases from the burner chamber.
- After the first 15 seconds of blower operation, the blower is switched to LO speed. The right extender glow plug relay (LER) is energized for 45 seconds which will close the LER contacts enabling the right extender glow plug to receive system power.
- After the glow plug has been energized for 45 seconds, the right extender fuel solenoid is energized for 2 seconds which allows fuel to be sprayed on the glow plug.
- The ECM will detect whether the burner ignites with input from the right extender flame sensor. If the burner has ignited, a run cycle is initiated. If the burner has failed to ignite, the right extender fuel solenoid is deenergized which will turn OFF the fuel spray.
- When the fuel spray is turned OFF, the glow plug and the blower will remain ON for another 15 seconds. The right extender fuel solenoid will be energized for 2 seconds again which will allow fuel to be sprayed on the glow plug again.
- The ECM will attempt Step 4 and Step 5 three times. If the burner fails to ignite, all of the components for the burn cycle are turned OFF and a diagnostic code will be logged.
When the flame sensor indicates that a flame is present, the ECM initiates a burner run cycle. During this cycle, the blower is operated at HI speed, the fuel valve is OPEN and the glow plug is OFF. The burner will stay in this condition until one of the following conditions occur:
- The temperature switch opens indicating that the burner is hot enough.
- The flame sensor detects that the flame has gone out. A flame out diagnostic code will be logged.
- Twenty minutes have elapsed. A failure to reach temperature diagnostic code is logged.
- If the burner system switch or burner mode switch is turned to the OFF position.
If one of the above conditions occur, the right extender fuel solenoid will be deenergized which will turn OFF the fuel spray. The blower will remain ON. After at least 5 minutes of time have elapsed, the ECM will attempt to ignite the burner again if all conditions are met.
OFF Mode
When the mode switch is in the OFF position, the ECM will not attempt a burner ignite cycle. If the burner is already ignited, the ECM will stop the burner run cycle which will cause the burner to turn OFF, however, the blower will remain ON.
MANUAL Mode
If the key switch is ON and the mode switch is in the MANUAL position, the ECM will initiate a burner ignite cycle. The ECM will disregard the input status of the temperature switch and the flame sensor. The following sequence of events will occur:
- The temperature switch input is disregarded. The ECM initiates the burner ignite cycle.
- The blower is operated at HI speed for a 15 second purge cycle.
- A 45 second glow plug warm-up with the blower at LO speed will occur.
- Fuel sprays on the glow plug for 2 seconds. Then the blower speed goes to HI.
- Flame sensor input to the ECM is disregarded, the ECM assumes that the flame has ignited.
- The fuel will be sprayed into the burn chamber until 20 minutes of time has elapsed or until the burner system switch or the burner mode switch is moved to the OFF position.
The burner will remain OFF until the operator moves the burner mode switch to the OFF position and then back to the MANUAL position. MANUAL mode should only be used if it is determined that the temperature switch or the flame sensor is malfunctioning and a replacement is not available or convenient at the time.
Note: In MANUAL mode, the fuel valve will continue to spray fuel into the burner chamber regardless of whether it ignited successfully or not. The operator must watch the burner to make sure it has ignited successfully. The burner will only cycle once in the MANUAL mode. The burner will not turn back on until the switch has moved to the OFF position and then back to the MANUAL position. The operator must remember to turn the burner on again if the temperature is too low.