Stihl MS 461 - 13 Heating System; Carburetor Heating; Testing the Complete System; Testing the Heating Element

93MS 461, MS 461-R
13. Heating System
13.1 Carburetor Heating
The heating element is installed
between the filter base and
carburetor. Current is supplied via
wires to the heating element.
The heating element is controlled by
a thermostatic switch on the
underside of 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.
13.1.1 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
specified in the carburetor
heating troubleshooting chart,
b 13.2
– Remove the shroud, b 6.4
– Remove the air filter, b 12.1
– Remove the baffle, b 12.2
– Set the ohmmeter to measuring
range "Ω".
: Clip one of the two test leads to a
nut on the flange and the other to
a cylinder fin.
– If the system is in good condition
the ohmmeter will indicate a
value of about 8 Ω in measuring
range "Ω".
If the reading obtained is outside
this tolerance, test each component
separately.
13.1.2 Testing the Heating
Element
– Remove the filter base, b 12.3
– Remove the baffle plate, b 12.4
: Pull the insulating tubes (1) with
connectors out of the guides.
100
50
30
20
10
5
0
20
10
5
3443RA327 TG
3443RA287 TG
1
1
: Push back the insulating
tubes (1) in the direction of the
heating element (2) and separate
the pin and socket connectors.
– Insulating tubes may be left on
the wires.
: Remove the heating element (2).
– Inspect the gasket and replace if
necessary.
: Clip one test lead to the heating
element (1) and the other to the
connector pin of the black
wire (2).
If the heating element is in good
condition the ohmmeter will indicate
a value of about 8 Ω in measuring
range "Ω".
– If these readings are not
obtained, install a new heating
element.
3443RA294 TG
1
1
2
100
50
30
20
10
5
0
20
10
5
2
1
2
3443RA486 TG