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Instruction Manual
IM-106-340, Rev. 4.0
May 2006
8-7
Oxymitter 4000
Figure 8-3. Fault 1, Open Thermocouple
Fault 1, Open Thermocouple
Figure 8-3 shows the electronic assembly for an
Oxymitter 4000 with a membrane keypad (upper
view) and a Oxymitter 4000 with an LOI (lower
view). The upper view also shows J1 and test
points TP1 through TP6, located on the
microprocessor board, below the membrane
keypad or the LOI module.
Membrane Keypad
When Fault 1 is detected, the HEATER T/C LED
flashes once, pauses for three seconds, and
repeats.
1. Check connector J1. Ensure the connector
is properly seated.
2. Using a multimeter, measure the voltage
from TP3+ to TP4-. If the reading is 1.2
VDC ±0.1 VDC, the thermocouple is open.
3. Remove power. Disconnect J1. Measure
the resistance across the red and yellow
thermocouple leads. The resistance should
be approximately 1 ohm.
4. If the thermocouple is open, see "Heater
Strut Replacement" in Section 9:
Maintenance and Service.
LOI
When Fault 1 is detected, the LOI displays the
"O2 T/C Open" message.
1. Remove power. Unscrew and remove the
LOI module from the electronic assembly.
2. Reconnect power to the Oxymitter 4000.
3. Perform the diagnostic steps 1 through 4
shown for the membrane keypad.
37260019
LOI
KEYPAD
DIAGNOSTIC
ALARMS
TEST
POINTS
HEATER T/C
HEATER
O2 CELL
CALIBRATION
CALIBRATION RECOMMENDED
O2 CELL mV +
O2 CELL mv -
HEATER T/C +
HEATER T/C -
INC INC
DEC DEC
HIGH
GAS
LOW
GAS
CAL
TEST GAS +
PROCESS -
% O2
SW2
TP1
J1
TP2
TP3
RED
YEL
GRN
ORG
TP4
TP5
TP6
ON
Alarms
O2 T/C Open