Honeywell ML7984 - Troubleshooting Guide

Troubleshooting Guide for ML Valve Actuator
ML6984, ML7984 DIRECT COUPLED VALVE ACTUATORS
12
SYMPTOM
Valve leaks or will not
close off fully.
Noisy motor
Motor overheats/
smoke/component
burnt-out
ML will not respond
Vdc/mA signal drops
when connected to ML
ML 6984 will not close
or lock-up when used
with T87
POSSIBLE CAUSES
*Wrong actuator used and/or system
pressure too high
*Actuator not properly installed
*Incorrect DIP switch settings
*Bearing failed due to overheat
*Brushes worn out
*Current sensing circuit failed or
electronic components failed
LED (on):
*Incorrect DIP swtich settings
*No control signal present
*Incorrect wiring connections
*Incorrect signal polarity
*Internal time delay
LED (off):
*No or Low power supply
*Error mode
*Signal degradation due to
incompatible load impedance
*T87 Colling Anticipator caused
current shunting to the ML
ACTIONS
*Check valve close-off rating
*Check voltage at actuator terminals
*Ensure valve stem is fully threaded into brass
drive shaft and locked in place with the set
screw.
*Check against Product Instruction Sheet
*Check for excessive temperature and replace
complete actuator
*Use high temperature bit
*Check for excessive cycling and replace
brushes (Part #272775)
Replace actuator. Make sure:
*Correct actuator used
*Properly installed
*Do not adjust any calibration pot
*Proper voltage supply
*Applied according to ML specifications
*Use high temperature bit
*Check against Product Instruction Sheet
*Check controller
*Check against Product Instruction Sheet
*Check against Product Instruction Sheet
*Allow at least 1/2 second for the ML to respond
*Check voltage on T5 & T6 terminals
*Check valve stroke
*Check Controller Output and ML Input
Impedance specifications
*Use Series 2-ML6984 (Date Code 0049) or cut
T87 Cooling Anticipator resistor