Genie S-80, Service Manual

Page: 150 / 353

Section 4 • Repair Procedures
4 - 60 S-80 • S-85 • S-80X Part No. 122985
February 2012
MANIFOLDS
How to Test a Coil Diode
Genie incorporates spike suppressing diodes in all
of its directional valve coils except proportional
valves and those coils with a metal case. Properly
functioning coil diodes protect the electrical circuit
by suppressing voltage spikes. Voltage spikes
naturally occur within a function circuit following the
interruption of electrical current to a coil. Faulty
diodes can fail to protect the electrical system,
resulting in a tripped circuit breaker or component
damage.
Electrocution/burn hazard. Contact
with electrically charged circuits
could result in death or serious
injury. Remove all rings, watches
and other jewelry.
1 Test the coil for resistance. Refer to, How to
Test a Coil.
2 Connect a 10

resistor to the negative terminal
of a known good 9V DC battery. Connect the
other end of the resistor to a terminal on the
coil.
Note: The battery should read 9V DC or more
when measured across the terminals.
3 Set a multimeter to read DC current.
Note: The multimeter, when set to read DC
current, should be capable of reading up to 800
mA.
a multimeter
b 9V DC battery
c 10

resistor
d coil
Note: Dotted lines in illustration indicate a reversed
connection as specified in step 6.
4 Connect the negative lead to the other terminal
on the coil.
Note: If testing a single-terminal coil, connect the
negative lead to the internal metallic ring at either
end of the coil.
5 Momentarily connect the positive lead from the
multimeter to the positive terminal on the 9V DC
battery. Note and record the current reading.
6 At the battery or coil terminals, reverse the
connections. Note and record the current
reading.
Result: Both current readings are greater than
0 mA and are different by a minimum of 20%.
The coil is good.
Result: If one or both of the current readings are
0 mA, or if the two current readings do not differ
by a minimum of 20%, the coil and/or its
internal diode are faulty and the coil should be
replaced.
9V
BATTERY
10
RESISTOR
W
AMMETER
COIL
+
-
+
-
d
a
b
b
c
c