Proheat X45–School Bus - Manual (Page 54)

The ON/OFF switch (or Timer) lamp and the PCM “ON” LED will light. In addition,
the Hour Meter (Auxiliary Output) will be powered. The PROHEAT goes to
“Precheck”.
The PCM performs a short diagnostic cycle. This takes a few seconds to check
components for proper ranges, checking for the presence of a flame, short-
circuits and open circuits. If there are no errors indicated, the PROHEAT goes
to “Ignition”.
The blower starts first, followed by the coolant pump, ignition spark, air compressor
and fuel pump. The ignition electrode sparks for 60 seconds. Once the flame
sensor detects a good flame, the PROHEAT goes to “Full Output". At 60 seconds,
the sleeper fan output turns on (if equipped. See page 4-2 for more information).
The PROHEAT runs at Full Output until the coolant temperature reaches
185°F (85°C) at the heater outlet. The PROHEAT shuts the flame off and goes
to “Cool Down (Purge)”. Pu is displayed on the Proheat Control Module (PCM).
The air compressor and fuel pump shut off immediately. The blower and coolant
pump continue to run. After 3 minutes, the blower stops and the PROHEAT
goes to “Standby.”
MODES OF OPERATION
1. Switch “ON”
Standard
Mode Signal
2. Precheck
3. Ignition
4. Full Output
5. Purge
STANDARD MODE – All Models
The PCM comes in a "Sleeper Fan" or "Aux Input" model. The PCM model can
be identified by looking at the decal as shown on page 4-2. Depending on the
model and installation (refer to electrical drawing), the X45 has only the Standard
Mode of Operation or combination of Standard, Preheat and Supplemental
Modes of operation. The following table defines the applicability:
Aux Input Operation Mode Summary
See page 3-18 for background information.
Operational Mode Sleeper Fan Model Aux Input Model
Standard Yes Yes
Preheat no Yes
Supplemental no Yes
4-5 SECTION 4. PRINCIPLE OF OPERATION
4.2
4.2.1
Standard Heat Mode
• normal operation of the
Proheat
• over-rides and drops out
preheat mode
• overrides supplemental
mode
Supplemental Heat Mode
• similar to standard mode
except: coolant pump
does not run when
Proheat is not firing
• overrides and drops out
preheat mode
• 30 second signal required
before mode enabled
• 30 second signal removal
before mode shut off
Preheat Mode
• similar to standard
mode Except: 90 minute
time out
• activated via momentary
contact push button
switch with latching
internal to the PCM