Thermo Pro 90 5 Faults, Troubleshooting
506
17 Vehicle fan Check fuse F1
Observe coolant temperature (K5 switches at
approx. 25 °C)
Check switching signal on the relay K5, ground on
Pin 85 and positive on Pin 86 (audible, also see wiring
diagram in general installation instructions)
Check coolant temperature signal wire (green/white,
gn/wh), Pin 86 on K5
18 Control unit/
heater locked
Determine error cause for lock-out, then eliminate
lock-out.
A distinction is made between 3 types of lock-out:
– Fault lock-out
Unlocking by pressing ON/OFF switch
–ADR lock-out
See Fault lock-out
When ADR is triggered by the auxiliary drive, it
must be deactivated before switching on the
heater again
– Heater lock-out
Unlock:
1) Switch on heater (with switch or standard
timer)
2) Remove fuse F3 for at least 10 s.
3) Switch off heater (only with switch).
4) Reinstall fuse F3.
19 Burner unit Dismantling and visual inspection
20 Sooting:
Exhaust gas
temperature
has increased
to maximum
permissible
value.
Dismantling and visual inspection of burner unit,
exhaust temperature sensor, combustion pipe and
heat exchanger
Clean or completely replace
depending on condition
21 Optional room
thermostat
Room thermostat B4 does not switch Clean or replace compo-
nents
Check connection
Error point Component Recommended workshop action Parameter
Fig. 502 Overview of functional test of heater and its components
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