HST, VST
FAULT ANALYSIS
A. Furnace Does Not Heat Up
1.
The HEAT light
is ON
Æ
The heating
element has failed
Æ
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
Æ
The thermocouple has broken or has a
wiring fault
The controller
shows a low
temperature
Æ
The door switch(es) (if fitted) may be
faulty or need adjustment
Æ
The contactor (if fitted) may be faulty
Æ
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
Æ
The SUPPLY
light is ON
Æ
The controller may be
faulty or not receiving a
supply due to a faulty
switch or a wiring fault
Æ
The SUPPLY
light is OFF
Æ
Check the supply fuses and
any fuses in the furnace
control compartment
B.
Furnace Overheats
1.
The HEAT light
goes OFF with
the instrument
switch
Æ
The controller
shows a very high
temperature
Æ
The controller is faulty
Æ
The controller
shows a low
temperature
Æ
The thermocouple may have been shorted
out or may have been moved out of the
heating chamber
Æ
The thermocouple may be mounted the
wrong way round
Æ
The controller may be faulty
2.
The HEAT light
does not go off
with the
instrument
switch
Æ
The SSR has failed
“ON”
Æ
Check for an accidental wiring fault which
could have overloaded the SSR
7.0
MF13 11
