Auto-Zone Control Systems Auto-Zone CV & CV-EX Systems Installation & Operation (Version 01C) - Manual (Page 103)

Auto-Zone CV & CV-EX
Section 4
Start-Up and Troubleshooting 4-25
Checking CommLink Driver – CV-EX
Diagram
Set Your Meter
To Read DC Volts
+ -
+ -
+
- T-To-G
+3.1 VDC
To
+3.2 VDC
R-To-G
+3.4 VDC
To
+3.6 VDC
Communications
Loop
Disconnected
CommLink IV
To 24 VAC
Power Supply
MODEM
RS-232
Serial #
COMPUTER
USB
10/100
ETHERNET
DIAG
24
V
T
T
G
G
R
R
GN
D
485 LOOP
485 LOOP
POWER ACT LNK USB
C onf
ig
No
rm
a l
The CommLink IV Must Be
Powered Up For These Tests
Overview
This test checks for proper Network Loop voltages coming from the CommLink IV.
Tip: The Loop LED (located on the front panel) should “flicker” when the CommLink
is attempting to communicate. The Loop LED will flicker more noticeably for a
few seconds when first powered up. If the LED does not flicker, the unit is not
functioning.
Proper loop voltages are essential for reliable communications. It is normal to see fluctua-
tions at this point on the CommLink. The average value should be close to the acceptable
range described below. Values will vary upon initial powerup for about 10-15 seconds as
the unit attempts to communicate.
Measurements
Local Loop Acceptable Range
T - G (SHLD) 3.1 - 3.2 Volts DC
R - G (SHLD) 3.4 - 3.6 Volts DC
Action
Condition Action
If voltages are too high or too
low on either side. 1. The CommLink IV has a damaged comm driver chip.
Replace the CommLink IV. The driver chip is not
field-replaceable.