Troubleshooting - PHP Heat Wagon LVF90A Service Manual

High Pressure Troubleshooting
To use the troubleshooting section, look up the symptom you observe for the
possible causes. This section is based on the Master brand models B350 and
B600 manufactured by Desa. Other brands and models may differ somewhat,
but the troubleshooting and tests are applicable in most cases.
Symptoms:
Motor will not start, but ignition spark is present. Page 123.
Motor starts, but heater will not ignite. Page 124.
Heater ignites, runs less than one minute and the flame/safety control
trips. Page 126.
Heater ignites, runs several minutes and shuts down. Page 127.
Heater ignites, but combustion is poor or uneven. Page 128.
Motor and transformer do not operate. Page 128.
Heater ignites, but flame is excessive. Page 129.
Motor will not start, but ignition spark is present.
Causes:
1. Defective fan switch.
2. Fuel pump seized.
3. Defective motor.
4. Defective relay.
5. Motor reset button tripped.
Solutions:
1. Defective fan switch.
The fan switch may be tested with a multimeter set to ohms to check for con-
tinuity.
Usually the fan switch has three male terminals. The terminals may be num-
bered 1, 2 and 3. If not numbered here is the layout: 1 is the terminal with
the wire running to the motor relay, 2 is the terminal whose wire comes from
a terminal block fed power from the power cord and 3 is the terminal whose
wire comes from a terminal block fed by the flame/safety control. Remove the
fan switch and place the multimeter probes on terminals 1 and 3. Continuity
or zero ohms should be read. Next heat the "face" of the fan switch with a
lighter or other heat source. Place the multimeter probes on terminals 1 and
2, and again continuity should be read. If either reading fails to show conti-
nuity, the fan switch is defective.
123