Auto-Zone Control Systems Auto-Zone Basic Systems Installation & Operation (Version 02C) - Manual (Page 128)

Section 4 Auto-Zone Basic
4-26 Start-Up and Troubleshooting
Problem Possible Cause Solution
3
Bad Zone Sensor
Faulty Wiring/Sensor
An alarm occurs if the zone tempera-
ture reading is below 40
°F or above
105
°F. If actual temperature at the sen-
sor is between these temperatures and
an alarm occurs, start troubleshooting
at the zone sensor. Measure the sensor
voltage either at the sensor or the Zone
Controller. If it does not match the
chart, remove it from the wall, discon-
nect its wires and measure the resis-
tance between TMP & GND. Resis-
tance should compare to values in the
Temperature/Resistance chart. (Re-
member, temperature of sensor may be
affected by the heat of your hands). If
the resistance is significantly different
from the chart, replace the sensor. On
3-wire sensors with a “Warmer-
Cooler” pot, the resistance between
AUX & GND should vary from 10K to
15K Ohms depending on the position
of the pot. If the resistance is accept-
able, check the wiring between the sen-
sor and the controller by reconnecting
the sensor and going to the zone con-
troller, lifting the sensor terminal plug,
and reading the resistance in the wires.
Reversing TMP and GND wires on a
3-wire sensor will significantly affect
the readings. In checking sensor wir-
ing, also check for loose strands of
braided wire shorting to ground at the
terminals that may affect readings.