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SECTION 34 - DIAGNOSTICS AND TROUBLESHOOTING
Digital Outputs Troubleshooting
If any of the Digital Outputs tests fail to perform as
described above, perform the following steps in se-
quence. See Figure 37 on page 104 and applicable
wiring diagram referenced at the beginning of SEC-
TION 27 - LARGE TONNAGE CHILLER (LTC) I/O
BOARD 031-02895-000/001. If a defective component
is found during any of the steps, replace the component
as instructed and repeat the procedure above to deter-
mine if the problem has been resolved.
1. Remove I/O Board ribbon cable. Using an Ohm-
meter, perform a continuity test on the cable J1-25
to J19-25, J1-26 to J19-26 and applicable output
pin of function that failed in procedure above. If
an open circuit is detected, replace ribbon cable.
Otherwise, install ribbon cable and proceed to
next step.
2. Measure the +12 VDC supply voltage to the I/O
Board on I/O Board between J1-26 (+12 VDC)
and J1-25 (GND). If greater than 11.0 VDC, pro-
ceed to next step. If less than 11.0 VDC, discon-
nect ribbon cable at I/O Board J1 and repeat mea-
surement at JI. If less than 11.0 VDC, replace the
microboard. Re-install the ribbon cable.
3. Using the Digital Outputs procedure above, select
the output that failed the Digital Output test above.
4. Press ENABLE OUTPUT key. The LED adja-
cent to the selected output will illuminate. The
appropriate Microboard output pin at J19 for the
selected output should be at a Logic Low level
(less than 1.0 VDC). If it is greater than 1.0 VDC,
replace the microboard. With the output at a Logic
Low, the following should occur:
a. If a relay is selected as the output, the con-
tacts of the relay should be closed. If they are
not closed, replace the I/O Board.
322
b. If a Triac is selected as the output, the Triac
5. Press DISABLE OUTPUT key. The LED adja-
cent to the selected output will extinguish.
a. If a relay is selected as the output, the ap-
b. If a Triac is selected as the output, the ap-
Notes
The load (actuator) must be connected across the Triac
to determine the ON/OFF state of the Triac. The ON/
OFF state of the Triac can be determined by measur-
ing across the device (for example, TB1-3 to TB1-59 or
TB1-58 to TB1-59) with an AC Voltmeter. If the Triac
is turned on, the voltage will be less than 10 VAC. If
the Triac is turned off, the voltage will be greater than
100 VAC (Slide Valve Actuator) or greater than 20 VAC
(PRV, Hot gas or Refrigerant Level Control Actuator).
JCI COMPANY CONFIDENTIAL
ISSUE DATE: 10/25/2019
should be turned on. If the Triac has not
turned on, replace the I/O Board. See note 1
below for Triac testing.
propriate Microboard output pin at J19 for
the selected output should be at a Logic High
(greater than 10.0 VDC) level. With the out-
put at a Logic High level, the relay contacts
should be open. If they are not open, replace
the I/O Board. If it is less than 10.0 VDC,
remove the ribbon cable from J1 of the I/O
Board. On the I/O Board, measure the resis-
tance from J1-26 to the appropriate pin of J1
on the I/O Board for the selected relay. If the
resistance is greater than 100 Ohms, replace
the I/O Board. If the resistance is less than
100 Ohms, replace the microboard.
propriate Microboard output pin at J19 for
the selected output should be at a Logic High
(greater than 10.0 VDC) level. If it is less than
10.0 VDC, replace the microboard. With the
output at a Logic High level, the Triac should
be turned off. If the Triac has not turned off,
replace the I/O Board. See note 1 below for
Triac testing.
FORM 160.54-M1
JOHNSON CONTROLS
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