5
Fault Finding
12
Moffat Cobra Series - CF4
©
Moffat Ltd, August 2012
Amendment 4
Disconnect the connection between the
thermocouple and the flame failure valve and
measure the voltage using a multimeter.
If the voltage is over 10mV then there is a fault with
the flame failure valve electromagnet —
replace
the flame failure valve
.
If the voltage is under 10mV then the overtemp is
faulty or the pilot is too weak —
check the reason
for a weak pilot and rectify, or replace the over-
temp
.
Overtemp Tripped
Check the oil temperature with a thermometer.
If the oil temperature has reached over 220
°
C the
overtemp should have tripped (open circuit), and
cannot be reset until the temperature has dropped
below 192
°
C.
If the oil temperature is below 180
°
C and the over-
temp still cannot be reset, the overtemp is faulty.
Overtemp Faulty
To check if the overtemp is faulty, hold 'In' the gas
control ignition button and manually light the pilot
burners (Holding the control button depressed to
keep the pilot alight).
Using a multimeter, measure the voltage from the
gas control side of the thermocouple interrupter
block to earth. If the voltage is under 5mV (and the
thermocouple is generating at least 20mV) then the
overtemp is faulty—replace the overtemp.
If all of the above checks out satis, then check the
gas control valve or thermocouple.
Figure 5.2.1e.
Disconnect here
and Test
Flame Failure
Valve
Thermocouple
