Proheat M125 - Manual (Page 31)

MODES OF OPERATION 2.3
The G-II Proheat Control Module (G-II PCM) has three modes of operation: Standard,
Preheat and Supplemental. Depending on the installation, more than one mode
may be wired for operation. The wired modes may be identified by referring to the
installation wiring diagram to determine the G-II PCM pins on P2 Control that
have been connected. This wiring diagram may be compared with the drawing
in Section 1.2 Electrical. The following is a summary of the operation modes:
Standard Heat Mode
• normal operation of the
Proheat
• overrides and cancels
preheat mode
• overrides supplemental
mode
Preheat Mode
• similar to standard
mode Except: 90 minute
time out.
• activated via momentary
contact push button
switch with latching
internal to the G-II PCM
Supplemental Heat Mode
• similar to standard mode
except: coolant pump
does not run when
Proheat is not firing
• cancels preheat mode
• 30 second signal
required before mode
enabled
• 5 second delay required
for mode switch off
NOTE: Only the G-II PCM has an indicator light. See page C-1 for more information.
The ON/OFF switch lamp, timer G-II PCM or OEM indicator (installation options) will
light. In addition, the G-II PCM Indicator Light with turn ON GREEN. If the coolant
temperature is below 160°F (71°C) the PROHEAT enters Pre-check. If the
coolant temperature is above 160°F (71°C) the PROHEAT enters Standby.
The G-II PCM performs self diagnosis checking sensors for correct range,
electrical components for over-load and for a flame presence. Also during the
first Pre-check, the Ignition Module sparks for five seconds to allow a service
technician to visually check for a spark. If there are no errors indicated, the
PROHEAT goes to Ignition.
The Motor and Coolant Pump start first, followed by the ignition spark, and then
Fuel Solenoid Valve opens. The Ignition Module sparks for up to 30 seconds
during which time the flame sensor must detect a correct flame.
• If the PROHEAT detects proper flame at any time during the 30 second
ignition cycle, the PROHEAT enters Full Output.
• If the PROHEAT does not detect proper flame during the 30 second ignition
cycle, the PROHEAT enters Cool Down (Purge). The PROHEAT will attempt
to start again moving into Pre-check after Cool Down (Purge). If the
second start cycle fails, the PROHEAT will enter Fault Shut Down.
The PROHEAT will continue in Full Output until the coolant temperature reaches
185°F (85°C) at the PROHEAT'S Dual Mode Temperature Sensor. The PROHEAT
closes the Fuel Solenoid Valve and goes into Cool Down (Purge).
The Motor and Coolant Pump continue to operate for three minutes. After three
minutes, the Motor stops and the PROHEAT enters Standby. The PROHEAT
will Cool Down (Purge) for three reasons:
• Coolant reaches 185°F (85°C).
• A fault is detected. Go to Section 4.0 Troubleshooting and Repair, page 4-1.
• The PROHEAT is operating in Ignition or Full Output when it is switched off.
1. Switch “ON”
Standard
Mode Signal
2. Pre-check
3. Ignition
4. Full Output
5. Cool Down
(Purge)
STANDARD MODE 2.3.1
GREEN
INDICATOR
LIGHT
2-6 PROHEAT M-SERIES G-II PCM SERVICE MANUAL