Install Instructions

A421 Series Standard Electronic Temperature Controls Installation Instructions
12
5. Press  and  simultaneously to return to the
Main screen.
Troubleshooting
Fault Codes
A421 Series controls display fault codes on the LCD as
described in Table 5.
Troubleshooting Procedure
1. Check for proper voltage to the A421 control.
a. Remove the cover by loosening the two
captive cover screws.
b. Use an AC voltmeter to check the voltage
between the COM and 120V or 240V terminals
on line-voltage models and the two 24V
terminals on low-voltage models. See Figure 4.
c. The voltage must be between:
• 20 and 30 VAC for 24 VAC applications
• 102 and 132 VAC for 120 VAC applications
• 177 and 264 VAC for 208/240 VAC
applications
d. If the voltage reading is not within the required
range, check the power source and input
power wires for problems.
2. Check for proper sensor operation.
a. Disconnect all power sources to control.
b. Using an accurate thermometer, take a
temperature reading at the sensor location.
c. Disconnect the sensor from the control.
d. Using an ohmmeter, measure the resistance
across the two sensor leads while the sensor is
at the temperature taken in Step 2b.
e. Consult Figure 12 to verify that the measured
temperature and resistance conform to
established temperature and resistance
values.
f. If the measured values conform to the values
in Figure 12, proceed to Step 3.
Figure 11: Adjusting Temperature in the
Restricted Menu
Table 5: Fault Codes Defined
Fault Code Definition System Status Solution
SF flashing
alternately with
OP
Open temperature sensor or
sensor wiring
Output functions according
to the selected sensor failure
mode (SF)
See Troubleshooting Procedure
. Cycle
power to reset the control.
SF flashing
alternately with
SH
Shorted temperature sensor
or sensor wiring
Output functions according
to the selected sensor failure
mode (SF)
See Troubleshooting Procedure
. Cycle
power to reset the control.
EE Program failure Output is off Reset control by pressing the MENU
button. If problems persist, replace the
control.