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6) Trouble Shooting
6.1 Trouble Shooting Guide
42011076-003 R2
© 2006 Honeywell International Inc.
“Manufactured for and on behalf of the Environment and Combustion Controls Division of Honeywell Technologies Sàrl, Ecublens, Route
du Bois 37, Switzerland by its Authorised Representative Honeywell International Inc.”
Honeywell Control Systems Ltd.
Arlington Business Park,
Bracknell, Berkshire
RG12 1EB
Technical Help Desk: 08457 678999
www.honeywelluk.com
Symptom (Fault
Message)
Possible Cause Remedy
The room thermostat
displays the symbol but
the receiver box relay does
not switch on.
This is normal operation. The receiver box
cycles the relay on and off for times proportional
to the demand signal (0-100%) from the room
thermostat. The symbol only indicates that the
demand value is greater than 0%.
Using the button change the
temperature setpoint by a few degrees.
The receiver box should switch the relay
on after a few seconds delay.
The receiver box does not
react to setpoint changes
on the room thermostat.
The room thermostat and receiver box are not
bound.
Reset the receiver box by pressing and
holding the push button for 15 seconds.
Then follow the binding / rebinding
procedure as described in section 5)
Additional Installation Information.
After the binding procedure
the red LED is on and the
green one is flashing once
every 3 sec on the receiver
box.
Incorrect or incomplete binding procedure.
Incorrect position of the room thermostat during
binding.
Repeat the binding procedure.
Repeat the binding procedure keeping
approx. 1 m distance between the receiver
box and the room thermostat.
The red LED on the
receiver box is illuminated
(Communication loss)
The receiver box receives no RF messages from
the room thermostat:
RF signal is blocked due to wrong location of the
room thermostat.
Room thermostat batteries are exhausted.
Re-locate the room thermostat following
instructions in section 2) Installing the
CM900 Wireless System.
Replace batteries in the room thermostat.
6.2 Diagnostic Mode
The CM927/921 room thermostat has a user accessible mode that provides information useful to a remote
service person and a means of checking whether the boiler is working. To access this move the slider
switch to the OFF position then press and hold the button for 5 seconds. The room thermostat will enter
the user settings mode. Next press and hold the and buttons together. The room thermostat will hold
the relay on for 5 minutes and the following information can be viewed on the display by pressing the
or buttons. : model ID, date code (WW/YY) & checksum.
Hereby, Honeywell declares that this CM927/CM921 room thermostat and HC60NG receiver box are in
compliance with the essential requirements and other relevant provisions of Directive 1999/5/EC, 73/23EC
and 89/336EC.