
Notes for trouble-shooting for
LAUDA Thermostats with P - electronics
G/Therm/Service/Fehler/Fehlpe1.doc
- 04.12.98
page 1 of 4
Each repair requiring the opening of the control part by means of tools and each work at the electronic part may only
be done by a trained technician !
Malfunction
Fault
Reason
Remedy
Green signal lamp of
mains switch not alight
Control fuse has actuated
Replace fuse on PCB
”MP Mains” 5 x 20; F4A
Overload on PCB
Replace PCB ” MP Mains ”
Display:
”Level too low ”
Bath level too low
Evaporation; external
consuming device not refilled
Fill in bath liquid; press reset
button twice
Leakage in hose connections
Check hoses and their connection;
if necessary replace them; fill in
bath liquid; press reset button
twice
Level detector
Check level detector, plugs and
hall sensors; if necessary replace
them; check their function carefully
For USH 400(/6) fill in bath liquid
up to the level mark
Display:
” Temperature too high ”
Temperature probe
Temperature difference between
two probes > 15°C
Replace bath temperature probe
(double Pt 100).
For USH 400(/6) please check
both single Pt 100.
Temperature of bath liquid
above over-temperature
switch-off point (To)
Overtemperature switch-off point
(To) set too low
Press reset button; adjust
overtemp. switch-off point (To) at
an higher value; press reset button
Triac or triggering
Replace triac or PCB "MP Mains"
Display:
” External fault "
Contact input 14 N ”Fault ”
is used
Pins ½ not connected
Reason for malfunction caused by
external system
No signal transmitter connected
to socket 14 N, though selection
at PAR level is activated
Switch off function ” Contact input
Fault ” at PAR level; see operating
instructions
Display:
” Ts > To
Wrong inputs
Setpoint adjusted above
overtemperature switch-off point
(To)
Adjust overtemperature switch-off
point (To) at an higher
temperature; pay attention to bath
liquid, flash point etc. !!
Overtemperature switch-off point
adjusted below setpoint (Ts)
First adjust setpoint (Ts) at a lower
value then set requested
overtemperature switch-off point
Display:
“Ts
<
Tu”
Wrong input
Setpoint adjusted below low-
temperature switch-off point
(Tu)
Adjust low-temperature switch-off
point (Tu) at a lower value
Low-temperature switch-off point
adjusted above setpoint
(Ts)
First adjust setpoint at an higher
temperature then set requested
low-temperature switch-off point
(Tu)