Proheat X45–School Bus - Manual (Page 56)

SUPPLEMENTAL MODE – Aux Input Models Only
The ‘ON” light and heater indicator will turn ON after 30 seconds of receiving
the signal. In addition, the Hour Meter (Auxiliary Output) will be powered.
The PROHEAT monitors coolant temperature until it drops below 150˚F
(65°C). Once coolant temperature drops below 150˚F (65°C) the PROHEAT
goes to “Pre-run”.
The coolant pump operates for 3 minutes to circulate coolant through the
system. If the coolant temperature rises above 150˚F (65°C), the pump shuts
off and the PROHEAT returns to “Supplemental Standby”. If the coolant
temperature remains below 150˚F (65°C), 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)”. 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 and Coolant Pump stop and
the PROHEAT goes to “Supplemental Standby” and repeats steps 2 to 7.
The “ON” light and the Heater Indicator turn off after 30 seconds of the signal
being removed. If the PROHEAT is in the “Supplemental Standby” or “Pre-run”
sequence the PROHEAT will turn off immediately. If the PROHEAT is in any other
function it will complete a “Cool Down (Purge)” function before turning off.
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
Supplemental
Signal for
30 Seconds
3. Pre-run
2. Supplemental
Standby
4. Pre-check
5. Ignition
6. Full Output
7. Purge
8. Remove
Supplemental
Signal for
30 Seconds
4-7 SECTION 4. PRINCIPLE OF OPERATION
4.2.3
NOTICE
There are special OEM versions for
Supplemental Mode. For example,
temperature thresholds may have a
low threshold of 160°F (71°C) rather
than 150°F (65°C) and a reduced
coolant pump Pre-run time of 30
seconds rather than three minutes.