10
TROUBLESHOOTING
The following text will assist in determining which of the two circuit boards (control panel or
microprocessor) may have failed.
Locate the symptom in the left column, then refer to the possible causes in the center column, then how to
test for cause in the right column.
SYMPTOM
POSSIBLE CAUSE
TEST FOR CAUSE
Display
not
coming On
Fan
not
coming On
1. No voltage at microprocessor
2. Broken or loose ribbon
connector
3. Failed control panel
1. Check across 2 red wires at
top of microprocessor for 12
volts AC.
2. Check across 2 pads on right
end of edge connector on
microprocessor for 5 volts DC
3. Check across temperature
sensor pins on control panel
for 5 volts DC (see page 9).
If
Yes - Replace board, No -
Replace ribbon connector
Display
not
coming On
Fan running
1. Failed control panel
2. Broken or loose ribbon
connector
1. Check across 2 pads on right
end of edge connector on
microprocessor for 5 volts DC
2. Check across temperature
sensor pins on control panel
for 5 volts DC (see page 9).
If
Yes - Replace board, No -
Replace ribbon connector
Display On
No heat
1. Program temperature lower
than oven temperature
2. Failed temperature sensor
3. Failed heat output on control
panel
4. Failed mechanical component
(contactor etc.)
1. Check program against
thermometer
2. Check sensor resistance.
3. Jump across 24 volt input and
Heat output wire on control
panel.
4. Place control into Manual
Back-up check operation
Display locks up on "88888"
Fan stops
1. Button being held down by
label
2. Low voltage at microprocessor
1. Check label for dents over
buttons.
2. Check across 2 red wires at
top of microprocessor for 12
volts AC.
Erratic temperature
Failed temperature sensor
Check sensor resistance (see
page 11).
TROUBLE SHOOTING
