Chapter 4
Troubleshooting
Problem C: Blower runs but heater fails to ignite
Listen carefully. You should hear a faint clicking noise fifteen to thirty seconds after the
blower starts. If you do, then:
1) Check the fuel system, especially that the propane tank(s) contain fuel and valve
is open on the tank(s). Confirm that the heater is getting fuel.
2) Check that the primary spark probe is connected to the top of the ignition module
and the quick connect on the end of the spark probe wire is securely connected to
both the ignition coil (see figure 7) and the spark probe wire. Check that the wire
for secondary spark probe is connected to the front of the combustion chamber.
3) Remove the cover to the thermostat and check that the heater is receiving at least
11.0 VDC while the blower is running. A voltage below 11 VDC typically
indicates a low battery or a problem in the electrical system between the heater
and the vehicle. If the voltage is this low, start the vehicle and try starting the
heater again. If the voltage is low with the vehicle running, there is a problem in
the electrical system between the heater and the vehicle. Start by looking for loose
or corroded connections.
4) Check the sail switch on the blower. First
check if the wires are attached. With the power
to the heater off, check the resistance between
the two terminals on the sail switch (or on
older models with three terminals the wires
should be attached to the the two terminals on
the right side). Push the front of the switch
closed to simulate the blower running as
shown in figure 8. The resistance should be
less than 1 ohm. If not replace the sail switch.
Also check for a good connection between the
rightmost terminal on the sail switch (see
figure 8) and ground. This resistance should be
less than 1 ohm. If it is not, remove the cover to the combustion chamber and
check the wiring to the high temperature limit switch. If the wiring is attached and
in good condition, check the resistance across the limit switch. If the resistance is
more than 1 ohm replace the switch.
5) Check the primary spark probe. Remove the burner cover from the combustion
chamber and the spark probe on the right side of the burner. The metal tip of the
spark probe should only be slightly rounded, the spark probe should only have
light deposits on the insulator, and the ceramic insulation should be undamaged. If
the spark probe is damaged or excessively round, it should be replaced. If the
spark probes has only deposits, carefully remove them with a damp rag or
abrasive plastic pad.
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Figure 6: Sail Switch
