Troubleshooting - Lang Purple Product Manual

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
Display not coming On
Fan not coming On
Display not coming On
Fan running
Display On
No heat
Display locks up on "88888"
Fan stops
Erratic temperature
POSSIBLE CAUSE
1. No voltage at microprocessor
2. Broken or loose ribbon
connector
3. Failed control panel
1. Failed control panel
2. Broken or loose ribbon
connector
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. Button being held down by
label
2. Low voltage at microprocessor
Failed temperature sensor
10

TROUBLESHOOTING

TEST FOR CAUSE
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
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
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
1. Check label for dents over
buttons.
2. Check across 2 red wires at
top of microprocessor for 12
volts AC.
Check sensor resistance (see
page 11).
TROUBLE SHOOTING