Proheat X45–School Bus - Manual (Page 62)

5-5 SECTION 5. TROUBLESHOOTING & REPAIR
Function Errors:
1 – Start 4 – Overheat
2 – Flame Out 5 – Voltage
3 – Coolant Flow
Errors displayed on the PCM diagnostic panel will cause the heater to shut
down. These diagnostic codes are usually the result of a system problem.
It is possible to have two or more diagnostic codes displayed at the same
time. A function diagnostic code may be displayed in conjunction with a
component diagnostic code.
FUNCTION DIAGNOSTICS
A START diagnostic code. Indicates that the flame sensor did not see a flame
during the FULL 60 second ignition period.
If the START diagnostic code is displayed, switch the heater “OFF” and then
“ON” to restart. Observe the exhaust and the heater operation through the
inspection window.
Troubleshoot the Flame Out diagnostic code based on:
1 Fuel System.
Go to page 5-6 to page 5-12, Steps 1 to 5.
• There is no fuel, fuel odor or atomized fuel coming from the exhaust pipe.
• There is no hot exhaust coming from the exhaust pipe.
• There is no flame visible through the inspection window.
2 Ignition System.
• There is raw fuel and/or atomized fuel and a raw fuel odor coming from
the exhaust pipe. Go to page 5-13.
• There is no hot exhaust coming from the exhaust pipe.
• There is no flame visible through the inspection window.
3 Flame Sensor.
Go to page 5-14.
• There is a flame and the combustion sounds good, the PROHEAT
appears to be operating normally.
• No smoke, raw fuel odor or atomized fuel is coming from the exhaust pipe.
Fuel System Schematic
The PROHEAT X45 fuel system operates on a venturi-style atomizing nozzle
technology. It operates similarly to a compressed air paint sprayer.
As shown in Figure 5-3, when the compressor/fuel pump motor is on, fuel is
drawn from the tank through the fuel pump and pressurizes the high pressure
side of the fuel regulator. The fuel regulator reduces the fuel pressure supplied
by the fuel pump to atmospheric pressure. Compressed air flowing through the
nozzle creates a venturi or suction effect which siphons fuel from the regulator. If
the compressed air flow through the nozzle stops, the regulator closes, shutting
off the fuel flow.
Also shown in Figure 5-3 is the electrode and the flame sensor. The electrode
provides the spark to ignite the fuel and the flame sensor is an optical device
which “sees” the flame.
1 Start
5.1.2