Market Forge Industries 2500 HE Service & Parts Manual page 18

3. INDICATOR LIGHT FAILS TO LIGHT WITH THERMOSTAT SET, FAN OPERATING
a) Indicator light burned out
b) Thermostat contacts faulty
c) faulty wiring
4. ERRATIC OVEN TEMPERATURE
a) faulty thermostat operation
5.3 ELECTRICAL FAULT ISOLATION
Correction of an electrical failure first requires
isolation of the fault to a single circuit or component. In
most cases the nature of the failure and its effect upon
the operation of the oven will be sufficient to isolate it
to one or more circuit elements Table 5-2 is provided
as a guide for isolating electrical faults.
5.4 ELECTRICAL TROUBLE-SHOOTING
PROCEDURES
Before performing the trouble-shooting pro-
cedures in this section the serviceman must be
familiar with the function of all controls as described in
Section 3 and with the Principles of Operation
described in Section 4.
Electrical trouble-shooting procedures which
follow require access to components and terminals of
the operating controls and ignition control board
Electrical controls are reached by removing the control
panel as described in paragraph 6.4.1 Wiring and
terminal locations are shown in Figure 5-1. Figure 4-2
shows the circuit schematically
5.4.1 Incoming Power
Before trouble-shooting any of the electrical parts
or assemblies, make sure power is being supplied to
the junction box (Figure 7-1, #11). With power
connected to the oven, an a-c voltmeter is used to
measure 120 volts across terminals to lines coded L1
(hot lead to wi re #1) and L2
TABLE 5-1 (cont )
Replace light
Replace thermostat
Check wiring from door switch to thermostat and light
Recalibrate or replace as required See subsection 6.3.2
(neutral lead to wire #11) Make sure the unit is
properly grounded to the ground lug in the Junction
box If 120 volts are present, the fault lies in the
electrical circuits of the oven
5.4.2 Electrical Inspection
The first step in any electrical trouble-shooting
procedure is a thorough inspection of all wiring
connections To access the electrical components,
remove control panel as described in subsection 6.4.1
Before removing the control panel or checking
connections or wiring, make sure incoming
power is shut off When power is supplied, all
exposed terminals carry 120 volts
Check all connections by hand to ensure that all
connection points are tightly secured Use a
screwdriver to tighten if necessary Inspect all quick-
disconnect terminals for evidence of corrosion
Terminals in this condition should be replaced
5.4.3 Direct Spark Ignition System
The ignition control board and associated
components are the main electrical control for
operation of the HE oven If it is determined that the
electrical controls (solenoid valve, RESET switches,
electrode, etc ,) are not damaged and
5-2
WARNING