Proheat X45–School Bus - Manual (Page 55)

Push the Preheat button and the PCM “ON” LED will light will turn on. In addition,
the Hour Meter (Auxiliary Output) will be powered. The PROHEAT goes to
“Pre-check.”
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".
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).”
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.”
The coolant pump circulates the coolant through the system until the temperature
drops to 150˚F (65˚C) at the heater outlet. The Proheat returns to Precheck
and repeats steps 2 to 6. The PROHEAT will continue to repeat this cycle
until it is switched off, or will switch OFF automatically after 90 minutes.
If PROHEAT is in “Full Output”, it will Cool Down (Purge) first, then shuts off.
If PROHEAT is in “Standby”, it shuts off immediately.
When switched OFF, the Hour Meter (Auxiliary Output) will shut off.
NOTE: The PROHEAT will Cool Down (Purge) for 3 reasons:
• the coolant reaches 185˚F (85˚C)
• there is a function or component problem
(See Troubleshooting & Repair on page 5-1)
• the PROHEAT is operating at Full Output when it is shut "OFF".
1. Activate
Preheat Signal
2. Precheck
3. Ignition
4. Full Output
5. Purge
6. Standby
7. After 90
minutes or
Switched off
PREHEAT MODE – Aux Input Models Only
4-6 PROHEAT INSTALLATION & SERVICE
4.2.2
6. Standby
7. Switch “OFF”
The coolant pump circulates the coolant through the system until the temperature
drops to 150˚F (65˚C) at the heater outlet; then it will enter Precheck and
repeat steps 2 to 6. The PROHEAT will continue to repeat steps 2 to 5 until it
is switched “OFF.”
If PROHEAT is in Full Output, it will Cool Down (Purge) first, then shut “OFF”.
If PROHEAT is in Standby, it will shut “OFF” immediately.
When switched OFF, the sleeper fan output turns off (if equipped, see page 4-2).
When switched OFF, the Hour Meter (Auxiliary Output) will shut off.
NOTE: The PROHEAT will Cool Down (Purge) for 3 reasons:
•the coolant reaches 185˚F (85˚C)
•there is a function or component problem
(See Troubleshooting & Repair on page 5-1)
•the PROHEAT is operating at Full Output when it is shut “OFF”