Auto-Zone Control Systems Auto-Zone CV & CV-EX Systems Installation & Operation (Version 01C) - Manual (Page 98)

Section 4
Auto-Zone CV & CV-EX
4-20 Start-Up and Troubleshooting
Communications Loops
Checking CommLink Local Loop – CV
Diagram
MODEM
RS-232
Serial #
COMPUTER
USB
10/100
ETHERNET
DIAG
24
V
T G R GN
D
485 LOOP POWER ACT LNK USB
C onfi
g
No
rm
al
To
Zone Manager
Network Loop
The CommLink IV Must Be
Powered Up For These Tests
Set Your Meter
To Read DC Volts
+ -
+ -
+ -
+
-
To 24 VAC
Power Supply
T-To-G
+2.0 VDC
To
+4.0 VDC
R-To-G
+2.0 VDC
To
+4.0 VDC
CommLink IV
Overview
This test checks for proper loop voltages at the CommLink IV.
Tip: The Loop LED (located on the front panel) should “flicker” when the CommLink IV
is attempting to communicate. The Loop LED will flicker more noticeably for a few
seconds when first powered up. If the Loop LED does not flicker, the unit is defective.
Proper loop voltages are essential for reliable communications. It is normal to see fluctua-
tions at this point on the CommLink IV. The average value should be close to the accept-
able range described below. Values will vary upon initial powerup for about 10-15 sec-
onds as the unit attempts to communicate.
Measurements
Network Loop Acceptable Range
T - G (SHLD) 2.0 - 4.0 Volts DC
R - G (SHLD) 2.0 - 4.0 Volts DC
Action
Condition Action
If voltages are too high or too
low on either side. 1. Unplug the Comm loop from the CommLink IV and
Check for proper loop voltages. If a problem exists,
disconnect each CV Unit from the loop until the
problem is isolated.
2. Replace the CommLink IV. The driver chip is not
field-replaceable. See Page 4-22.