Spheros Thermo S 160, Workshop Manual

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Thermo S 160/230/300/350/400 5 Troubleshooting and error correction
507
5.4.3 Error symptom "Low voltage"
A value is stored in the control unit as smallest
"permissible low voltage".
It must be noted that the voltage may be lowered during
heater start, and that the "low voltage" threshold may be
violated.
Among others this depends on the vehicle electrical system,
the temperature of optional components, such as the nozzle
block preheater, circulating pumps or heatable filters.
NO
YES
Is the battery charge condition permanently
greater than 20.5V ± 0.5V?
Ensure permanent battery voltage greater
than 20.5V ± 0.5V.
Disconnect the A1 plug from the control unit.
Is the voltage between pin 2 and pin 1 of plug A1
at least 20.5V ± 0.5V?
Is the electrical connection to the heater OK?
(fuse, wiring harnesse s, plug connections,
pins, etc.)
Repair or replace the
electrical connection to
the heater.
Start heater: Is the voltage permanently applied to the heater during heater
start or during heating operation 20.5V ± 0.5V? (Verify with SST diagnosis.)
Ensure higher voltage during heater
start and/or heating operation.
Control unit defective, replace it.