Fault
Cause
Display shows NO
Faulty ribbon cable
INPUTS
Display shows
Faulty input, relay or output
4–20 BOARD
module
ERROR
or
RELAY BOARD
ERROR
or
OUTPUT BOARD
ERROR
LED and display test
Faulty display PCB
failed
"Power DC" LED is
Faulty power supply to the
not lit, but display is
control unit
on
Faulty display PCB
Display shows
Faulty transmitter connector Check the transmitter wiring
Under-range
Loop current incorrect
Faulty transmitter
Display shows Over-
Short circuit in the remote
range
sensor transmitter wiring
Faulty remote sensor trans-
mitter
The "Fault (F)" LED
Faulty transmitter wiring
lights up for a single
channel
Loop current incorrect
Faulty transmitter
Faulty input module
The "Fault (F)" LED
Faulty transmitter wiring
lights up for a group
of four channels.
Faulty ribbon cable
Faulty input module
Input module
Faulty ribbon cable
installed, but LEDs
do not light up or no
data for module on
the display
Faulty internal wiring
Faulty input module
Faulty display PCB
®
REGARD
3900
Fault elimination and messages
Remedy
Repair or replace ribbon
cable
Replace the faulty module
Replace display PCB
Check the internal or exter-
nal 24 V DC power supply
and repair
Replace display PCB
and repair
Re-calibrate
Replace the transmitter
Check the transmitter wiring
and repair
Check and repair the trans-
mitter
Check the transmitter wiring
and repair
Re-calibrate
Replace the transmitter
Replace input module
Check the transmitter wiring
and repair
Check ribbon cable and
repair/replace
Replace input module
Check ribbon cable and
repair/replace
Check the power distribution
internal wiring and repair
Replace input module
Replace display PCB