Operating instructions

5. Basic Troubleshooting
5.1 General Information
This section describes troubleshooting procedures for the Thermo 90 S coolant heater.
Troubleshooting is normally limited to the isolation of defective components.
5.2 General Failure Symptoms
The following table lists possible failure symptoms.
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Thermo 90 S 6 Basic Troubleshooting
CAUTION
Troubleshooting requires profound knowledge about structure and theory of operation of the heater
components and may only be performed by skilled personnel.
NOTE
After any correction of a defect a functional test has to be performed in the vehicle.
Before troubleshooting, check for and eliminate these defects:
- fuel supply (plugged fuel filter)
- corrosion on battery terminals
- blown fuses
- corrosion on electrical wiring and fuses
- corrosion on connectors
- loose contact on connectors
- wrong crimping on connectors
- shut down initiated by temperature limiter
NOTE
Coolant temperature must be below 167°F (75°C) to start up.