3-44
GTH-1256
Part No. 1272856
September 2016
Section 3 • Repair Procedures
7-2
Valve Coils
How to Test a Coil
A properly functioning coil provides an
electromagnetic force which operates the
solenoid valve. Critical to normal operation is
continuity within the coil. Zero resistance or in
fi
nite
resistance indicates the coil has failed.
Since coil resistance is sensitive to temperature,
resistance values outside speci
fi
cation can
produce erratic operation. When coil resistance
decreases below speci
fi
cation, amperage
increases. As resistance rises above speci
fi
cation,
voltage increases.
While valves may operate when coil resistance
is outside speci
fi
cation, maintaining coils within
speci
fi
cation will help ensure proper valve function
over a wide range of operating temperatures.
WARNING
Electrocution/burn hazard.
Contact with electrically charged
circuits could result in death or
serious injury.
Remove all rings, watches and
other jewelry.
Note: If the machine has been in operation, allow
the coil to cool at least 3 hours before performing
this test.
1 Tag and disconnect the wiring from the coil to
be tested.
2 Test the coil resistance using a multimeter
set to resistance (
Ω
). Refer to the Valve Coil
Resistance Speci
fi
cation table.
Result: If the resistance is not within the
adjusted speci
fi
cation, plus or minus 10%,
replace the coil.
Valve Coil Resistance
Speci
fi
cation
Note: The following coil resistance speci
fi
cations
are at an ambient temperature of 68°F / 20°C. As
valve coil resistance is sensitive to changes in
air temperature, the coil resistance will typically
increase or decrease by 4% for each 18°F / 20°C
that your air temperature increases or decreases
from 68°F / 20°C.
Description
Specifi cation
Steering modes selector valve,
3 position 4 way
12V DC with diode
5.6
Ω
Mechanical gear speed Selector
valve, 3 position 4 way
12V DC with diode
8.8
Ω
Forward/Reverse Selector valve,
3 position 4 way
12V DC with diode
8.8
Ω
Outrigger Selector valve,
2 position 4 way
12V DC with diode
8.8
Ω
MANIFOLDS
MANIFOLDS
