Railway Equipment 934, Operating Manual

Page: 34 / 62

P/N R9340-0104 34 © 2010 RAILWAY EQUIPMENT CO.
REV B
5/11
D. SNOW DETECTOR TROUBLESHOOTING
NOTE: A newly-installed snow detector sensing head should operate 15-20
minutes to allow the internal heater to reach normal operating temperature.
1. NO HEAT ON THE SENSING HEAD
a. Check for voltage between terminal post 9 and 11, and between terminal
post 9 and 12. It should be 18VAC (+2VAC). If not:
(1)
Check the display on the control module.
(2) The control transformer may be defective.
(3) There may be a bad circuit connection.
b. Remove the black and the green lead wires from the terminal posts.
Check resistance between them. If resistance is greater than 10 ohms, the
sensing head is defective and should be replaced.
2. DOES NOT DETECT MOISTURE
a. Clean the snow detector as described in Section VIII.C. SNOW
DETECTOR MAINTENANCE
b. If unit still does not detect moisture, check the wiring connections between
detector head and terminal posts.
c. If unit still does not detect moisture, replace the control module with a
known good control module. If still not operating properly, replace the
sensing head.
NOTE: If a snow detector head becomes saturated with moisture, it can
sometimes be restored to normal operation by removing it and “baking” it
in a conventional oven for several hours. Do not exceed 150 degrees F.
3. CONSTANT INDICATION OF MOISTURE DETECTION
a. Clean the snow detector heads as described in section C, Snow
Detector Maintenance.
b. Remove white lead(s) from terminal post 10. If moisture indication is still
on, the control module is defective and should be replaced.