Operating instructions

10. Temperature differential between water inlet and outlet should not exceed 10° C (18° F).
11. Vehicle equipped with sleeper heating option:
- turn vehicle ignition key to “ACC” position or switch Webasto thermostat “ON”.
- set thermostat in sleeper to highest heat position.
- the sleeper heat exchanger fan will blow warm air.
- turn thermostat down to lowest heat position and fan should cycle off.
12. Switch “OFF” Thermo 90 S heater and sleeper blower control.
13. Re-tighten hose clamps to 45 in/lb. (5 Nm) and inspect installation for leaks.
14. Complete the warranty card and send to Webasto Thermosystems.
15. Install the stainless steel enclosure cover if equipped.
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4 Installation Thermo 90 S
NOTE
Necessary information to complete warranty card and ensure full warranty coverage can be found
on the heater name plate.
NOTE
The engine temperature gauge may read than actual heater output temperature. This is due to the
location of the temperature gauge sensor on the engine.
NOTE
Installation with long fuel lines may need a second start attempt to prime the fuel lines. Cycle
ON/OFF switch to reset control unit.