Issue
All or a group of Analog Inputs on my Controller (DCU 7700) are reading high (flooding), in alarm and / or displayed as "OLD'.
Product Line
TAC INET
Environment
- I/NET
- All model series DCU 77xx
Cause
The inputs on a DCU 7700 are 1-5 Volt DC inputs.
If the voltage of an input goes above 5 Volts DC the voltage will flood across the other inputs and they will all go out of range or OLD.
Resolution
To diagnose the problem sensor perform the following:
- Measure all inputs (Between terminal 9 and the respective input terminal) one at a time and identify the input that is the highest voltage (above 5 Volts.)
- Disconnect this input and then place your meter between terminal 9 and the identified input terminal.
- The excess voltage will slowly drain away and all the other points will come back into normal operating range.
- If the voltage does not drop repeat the above steps.
- Replace / Repair the fault sensor(s).
Also refer to Analog inputs are reading too high or too low on a 7780.
