Troubleshooting Digital Temperature Controls

Digital Controls

# Problem Cause Solution
1 Control will not turn on - no power/electrical fusing/incorrect voltage. Main disconnect in an off position; open protector(s) or defective circuit breaker on main power supply or loose or disconnected wiring. Verify power and electrical connections by measuring voltage with a voltmeter. Test, reset or repair connections as required.
Improper Wiring Verify wiring with appropriate diagram and correct if necessary.
Single-phase power connected to lines L1/L2 instead of L1/L3 (combination type controls). Correct power connection points and return to service
Damaged or defective power switch. Replace switch.
Incorrect or defective control step-down transformer. Verify connections, voltage rating and output on transformer and repair or replace as required.
Incorrect/excessive voltage applied to control. Verify that applied voltage does not exceed 240 VAC. Add step-down transformer to system and replace damaged control.
2 Blank display. Sensor board not properly installed into the main circuit board. Remove and reinstall sensor board to assure proper connection and alignment.
Corrosion on display connections. Scrap/replace control. Do not operate control without rear cover.
Defective display. Return control to factory for repair/replacement.
Electrolytic capacitor failure on power supply line filter. Return control to factory for repair.
Diode failure. Return control to factory for repair.
Wire broken on line filter. Return control to factory for repair.
Transformer secondary open. Replace transformer, return to factory for repair.
Failed power supply. Return control to factory for repair.
Failed line filter. Return control to factory for repair.
Damaged connectors to power supply. Return control to factory for repair.
Failed voltage regulator. Return control to factory for repair.
3 Display cycles on/off when power is applied. Return control to factory for repair. Verify proper protector by product type/operating temperature and replace as required. (See catalog or installation sheet for available temperature ranges).
Failed capacitor causing noise on power supply. Return control to factory for repair.
4 Blank display on high/low end of operating range. Electrolytic capacitor failure on power supply line filter at 32F/1K or 511F/2K. Return control to factory for repair.
5 Erratic/unstable display. Sensor leads routed inside conduit with power leads. Shield or reroute sensor leads, adjust sensitivity of signal filter in configuration menu.
Excessive EMI/RFI on power supply Add line filter to power supply.
Electrolytic capacitor failure on power supply Return control to factory for repairs.
6 Control intermittently flashes ---/process temperature. Control in calibration mode intermittently. Recalibrate control and return to service.
7 Control displays A.001 when you enter calibration mode. Control parameters inadvertently changed while checking set point. Recalibrate control and check all configuration settings.
8 Low temperature displayed. Sensor placed below heat source/heat stratification in tank. Test sensor by placing known accurate thermometer and sensor in the same tank location. If they read the same the sensor is good and can be reused by securing the sensor above the bottom of the heat source. (Top third of solution depth.)
Defective sensor. Replace sensor.
Sensor extended with incorrect wire (thermocouple wire used instead of copper wire). Check sensor for any splices/extensions and replace with copper wire as required.
Display offset parameter (U2) set between –1 and –9. Reset U2 value to zero or to a value that matches the difference measured to an accurate thermometer.
Electrolytic capacitor not filtering power supply. Return control to factory for repair.
Failure of power supply board. Return control to factory for repair.
9 High temperature displayed. Damaged or incorrect sensor. Verify sensor type and function. Replace as required.
Display offset parameter (U2) set between +1 and +9. Reset U2 value to zero or to a value that matches the difference measured to an accurate thermometer.
10 Random irregular display. Incorrect sensor selection in U1 parameter of control setup. Reset U1 selection to match sensor being used.
Failed capacitor not filtering power supply. Return control to factory for repair.
11 Control displays "000". Incorrect sensor selection in U1 parameter of control setup. Reset U1 selection to match sensor being used.
Failed capacitor not filtering power supply. Return control to factory for repair.
12 Control displays "32"F or "0"C at all times. Calibration input for Cal 2 set at 1K. Reset input for Cal 2 to 2K.
13 Control displays/flashes "AAA". Measured temperature exceeds alarm set point value. Reset alarm set point to match application.
14 Control display changes very frequently. Display stabilizer (U8) value set to too high a value for process. Reset display stabilizer value (U4) to a lower value (default value is 10).
Electrolytic capacitor failure on power supply. Return control to factory for repair.
15 Heat/status lamp does not illuminate. Broken/damaged LED. Return control to factory for repair.
16 Mode keys do not operate properly. Control operated without rear cover on enclosure, which may allow the board to move back away from membrane front panel. Reinstall back cover of control and reset any affected parameters.
Control back panel incorrectly attached to enclosure. Reinstall back panel taking care to align top of back cover with the top of the control.
Corrosion on switches. Return control to factory for repair. Make sure rear cover is used during installation.
Bent lead on sensor board shorting to trace on main circuit board. Straighten leads to sensor board and reconnect to control.
17 Error message (HHH). Sensor value of RTD out of range (resistance value greater than 1000F/538C measured). Improperly connected or failed sensor. Remove RTD sensor, inspect for damage and test with ohmmeter to verify integrity (approximately 1007 ohms at 72F/22C). Replace/reconnect as required.
Calibration parameters changed.. Recalibrate control and reset all parameters.
Failed IC. Return control to factory for repair.
Broken or damaged line filter. Return control to factory for repair.
Improper solder joint. Return control to factory for repair.
Sensor used does not match control input settings. Verify/correct sensor type settings to match sensor.
18 Error message alternates between UUU and HHH. Failed capcitor. Return control to factory for repair.
19 Error message (UUU). Sensor value of RTD out of range low (resistance value less than –40F/40C measured). Shorted sensor, connections or sensor leads. Remove RTD sensor, inspect for damage to lead wires and connection. Test with ohmmeter to verify integrity (approximately 1007 ohms at 72F/22C). Repair/replace and reconnect as required.
Failed IC. Return control to factory for repair.
Control sensor parameter set for RTD while being operated with a thermocouple. Reset sensor parameter for sensor being used..
Failed capacitor loading down temperature input. Return control to factory for repair.
20 Error message (small "c" on lower left portion of display). Control not calibrated or calibration/setup information corrupted. Control is operating on preset default values. Reset calibration and input settings as listed in control manual (see appropriate manual for directions).
Control configuration values set for two wire RTD sensor but calibration parameters not changed from default values. Reset configuration to match sensor (see appropriate manual for directions).
21 Error message (large "C"). Control has never been calibrated or configured and is using default values. Reset configuration and calibration values as noted in the manual (see appropriate manual for directions).
22 Control will not turn on. Thermal protector from heater open or not connected into control circuit. Warning: Do not operate heaters without thermal protection. Making sure all power is off, verify thermal protector continuity with an ohm or continuity meter, replace as required and connect across terminal blocks as directed in wiring diagram.
Open coil on relay (combination type controls). Test relay by applying rated voltage to coil. Replace if defective.
Incorrect transformer or relay coil used. Check voltage ratings of components to make sure they match rating of secondary circuit. Replace as required.
No output voltage from step-down transformer (combination type controls). Test secondary side of transformer for appropriate output voltage and replace if required.
Corrosion on contacts of relay. Return control to factory for possible repair/relay replacement.
Excessive current through relay contacts. Check system for cause of excessive current. Add auxiliary relay as required. Return control to factory for repair.
23 Control loses calibration. Control inadvertently placed in calibration mode while checking set point. Recalibrate control per instructions.
Control enters calibration mode due to pressure against all three-mode keys. Remove rear cover, realign circuit board and reattach cover. Recalibrate control per instructions.
Corrosion on components. Scrap/replace control. Do not operate control without rear cover.
No output voltage from step-down transformer (combination type controls). Test secondary side of transformer for appropriate output voltage and replace if required.
24 Control relay contacts remain closed. Excessive current through relay contacts. Check installation for source of excessive current. Add auxiliary relay as required. Return control to factory for repair.
Solder bridge on relay input. Remove solder bridge.
25 Control relays remain open. Corrosion byproducts on relay contacts. Clean relay contacts. Do not operate control without rear cover.
Failed capacitor not filtering power supply. Return control to factory for repair.
Relay damaged due to electrical arc/over current Return control to factory for repair.
Defective relay. Return control to factory for repair.
26 Control will not calibrate. Failed electrolytic capacitor. Return control to factory for repair.
Mode switch failed in open position. Return control to factory for repair.
27 Temperature setting drifts upward after short system warm-up. Transistor failure. Return control to factory for repair.
28 Control will not exit stand-by mode. Failed Opto isolator. Return control to factory for repair.