Webasto DBW 46 Repair Manual download pdf (Page 12)

Webasto Thermo & Comfort N.A., Inc. 12 www.techwebasto.com

GENERAL DESCRIPTION DBW 2010/2020/300 COOLANT HEATERS

2.1 PARTS OF THE HEATER

2.1.1 ELECTRONIC CONTROL UNIT (1)

The control unit SG 1553 in 12 volt and 24 volt versions

is the central component to ensure controlled operation

and monitoring of combustion.

Figure 1: Control Unit

2.1.2 OVERHEAT FUSE (15)

The overheat fuse protects the heater from too high and

inadmissible temperatures. The overheat fuse contains a

fusible link that reacts when the temperature exceeds

138° C (280° F), and switches the heater off with a purge

cycle.

Figure 2: Overheat Fuse

2.1.3 TEMPERATURE LIMITER (17)

The temperature limiter is a thermostat that responds

(opens) at a temperature of 95° C (203° F). The

temperature limiter will automatically reset (closes) once

temperature falls well below 95° C (203° F). Once the

limiter has reset, the heater will have to be switched off

and back on to restore operation.

Figure 3: Temperature Limiter

2.1.4 TEMPERATURE CONTROL THERMOSTAT (16)

After the operating temperature has been reached, the

temperature control thermostat opens and shuts off the

heating cycle and a purge cycle begins. Once the

operating temperature drops to the lower temperature

threshold of the control thermostat, the thermostat

closes and another heating cycle begins, thus,

maintaining a consistent coolant temperature.

Figure 4: Temperature Control Thermostat

NOTE: DBW 2020/300 Only. An optional

control thermostat could be mounted in the

heating system in place of the control

thermostat located on the heater.

Control unit

Overheat Fuse (white wires)

Response temperature

138° C (280° F)

Temperature Limiter (green wires)

Switching temperature

– opens at 95° C (203° F)

Temperature Control Thermostat

Version 1 (red and green wires)

– opens at 75 ± 3° C (167 ± 6° F)

– closes at 68 ± 5° C (154 ± 9° F)

Version 2 (orange and white wires)

– opens at 70 ± 3° C (158 ± 6° F)

– closes at 60 ± 5° C (140 ± 9° F)

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Webasto DBW 46 Repair Manual Page 12

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