Heating System; Carburetor Heating; Testing The Complete System; Testing The Heating Element - Stihl MS 240 Instruction Manual

15.

Heating System

15.1

Carburetor Heating

Current is supplied via wires to the
heating element which is installed
between the air filter and carburetor.
The heating element is controlled by
the thermostat on the carburetor.
The heating element and
thermostatic switch should be
checked if running problems occur
when the cold engine is idling or
running at part load, particularly at
temperatures below freezing.
Idling problems with a hot engine
are also an indication of a fault in the
heating element or thermostatic
switch.
15.1.1 Testing the Complete
System
The generator and heating element
are checked in the following test
which should be performed at an
ambient temperature of at least
+ 20 °C (68 °F).
If the temperature is lower than
+ 13 °C (55 °F), the thermostatic
switch may close and produce false
readings.
– Test the heating system as
specifed in the carburetor heating
troubleshooting chart, b 15.2
– Remove the air filter, b 14.1
– Set the ohmmeter to measuring
range "Ω".
100
: Clip one of the two test leads to
the carburetor body and the other
to a cylinder fin (ground).
– If the system is in good condition
the ohmmeter will indicate a
value of about 8 Ω in measuring
range "Ω".
To ensure good electrical contact,
press the heating plate and the
heating element against the
carburetor during the
measurement.
If the reading obtained is outside
this tolerance, test each component
separately.
15.1.2 Testing the Heating
Element
2
– Remove the air filter, b 14.1
: Unscrew the nuts (arrows).
: Remove the heating plate (1) and
heating element (2).
– Remove the carburetor, b 14.2
: Push back the insulating tube in
the direction of the heating
element and separate the pin and
socket connector.
: Remove the heating element (1).
MS 240, MS 260, MS 260 C
1
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