W
EBASTO
S
CHOLASTIC
S
ERIES
7BASIC TROUBLESHOOTING
7-3
7.4 Test Procedures
1. Setup
- Remove connector blocks from heater control unit, inspect for loose wires, corrosion and proper wire
connections.
- Plug control unit connector blocks into tester.
- Set heater switch/timer to “ON” and turn vehicle heater valve to “FULL” mode (if equipped).
- Proceed to component test procedures.
2. Component Test Procedures and Results
WARNING
Do not attempt to test fire or run heater with burner head open. Ensure burner head is properly closed and secured
in place.
NOTE
Make sure the Water Pump and Motor Switches , are in the off position before connecting to the heater.
If not
- test input voltage at control
terminals B4(+) and B2(-)
- check battery connections
- check battery voltage
- test temperature fuse (if equipped)
- test overheat limiter
- test solenoid valve
- check electrode gap
- test ignition spark coil
ResultTest Step
BATTERY LED unit lights up
CONTROL THERMOSTAT LED
lights up
Tester connected
Push FUEL SOLENOID VALVE
button several times
clicking of solenoid should be heard
sparking should be heard
Push IGNITION SPARK COIL
button
Turn MOTOR switch “ON“
motor should run
- reset *inertia switch
- test motor
Turn WATER PUMP switch “ON“
pump should run
- test pump
Table 7-2: Test Procedures and Results
* Inertia Switch:
All 12 volt Scholastic Series heaters are equipped with a manual reset inertia switch usually located in the vicinity of
the burner head (look for a device with a round diaphragm red in color and about the size of a 25 cent piece on top).
The purpose of this switch is to stop heater operation in the event the vehicle is involved in an accident or receives a
strong impact shock, i.e. hitting a curb. This is done automatically by opening the combustion fan motor circuit,
stopping air and fuel delivery.
When troubleshooting, check to make certain inertia switch has not been tripped. Resetting is accomplished by
depressing the red diaphragm on top of the switch. You should hear an audible click when switch resets.
- test switch/ timer
- test control thermostat on heater
Normal operating range
- approx. 75 °C (167 °F) or higher
open (no heat required)
- approx. 68 °C (155 °F) or lower
closed (heat required)
