Instruction manual
13
6. The burner
seems to
cycle on and
off more than
it should.
7. The burner
starts, but the
main fan
never comes
on.
• Gas manifold pressure
• Dirt on main air blower or improper setup
of outlet air duct
• Burner sensor
• Heater Control Unit (HCU)
• Fan sensor
• Heater Control Unit (HCU)
• Blower motor relay
• Current overload on blower motor
• Blower motor
• Use a low pressure gauge (0-15 inches of water column) with 1/8” NPT inlet.
Install gauge in the pressure tap port located on the output side of the gas
valve. Run the heater. Adjust the pressure by turning the pressure adjusting
screw (located on the input side top of the gas valve) until the gauge reads 3”
W.C.(Propane) & 3.2” W.C.(Nat Gas). Refer to pipe sizing charts in the Heat
Wagon Engineering Guide. Heater requires 9-14” W.C. inlet pressure.
• Check for dirt or ice buildup on the air inlet or blower wheel. If using duct on
the air outlet, insure the back pressure does not exceed a static pressure of
.25” W.C. Check with low pressure gauge (0-15 inches of water column).
• On the heater control unit (HCU) disconnect the wires from terminals X10 and
X11. Using an ohm meter, check the resistance between the two wires for a
reading of 8K-15K ohms. Replace sensor if reading is out of range.
• If all of the above check good, replace the HCU.
• On the heater control unit (HCU) disconnect the wires from terminals X12 and
X13. Using an ohm meter, check the resistance between the two wires for a
reading of 8K-15K ohms.
• Turn the 3-position main switch to the fan position. If the blower runs, check the
fan sensor. If it is good, replace the HCU.
• Turn the 3-position main switch to the fan position. If the relay pulls in, check
for voltage between the L1 and L2 terminals. Then check the voltage between
terminals T1 and T2. The voltage should be the same. If it is much lower,
replace the relay.
• Turn the 3-position main switch to the fan position. Check for voltage between
the 2 solenoid coil terminals on the relay. If there is no voltage, the overload is
bad. Replace the motor and blower assembly.
• Turn the 3-position main switch to the fan position. Check for voltage between
terminals T1 and T2 on the motor relay. If the voltage is good, replace the
motor and blower assembly.
V
G175 TROUBLESHOOTING
Symptom
Possible Causes Possible Solutions