12
MF12 3.12
6.0
F
AULT
A
NALYSIS
A.
Furnace Does Not Heat Up
1.
The
HEAT
light
is
ON
The heating
element has failed
Check also that the SSR is working
correctly
2.
The
HEAT
light
is
OFF
The controller
shows
a very high
temperature
or a
code such as S.br
The thermocouple has broken or has a
wiring fault
The controller
shows a
low
temperature
The door switch(es) (if fitted) may be
faulty or need adjustment
The contactor (if fitted) may be faulty
The SSR could be failing to switch on due
to internal failure, faulty logic wiring from
the controller, or faulty controller
There are no lights
glowing on the
controller
Check the supply fuses and any fuses in the
furnace control compartment
The controller may be faulty or not
receiving a supply due to a faulty switch or
a wiring fault
B.
Furnace Overheats
1.
The
HEAT
light
goes
OFF
with
the instrument
switch
The controller
shows a
very high
temperature
The controller is faulty
The controller
shows a
low
temperature
The thermocouple may have been shorted
out or may have been moved out of the
heating chamber
The thermocouple may be mounted the
wrong way round
The controller may be faulty
2.
The
HEAT
light
does not go off
with the
instrument
switch
The SSR has failed
“ON”
Check for an accidental wiring fault which
could have overloaded the SSR
