Genie Z-30/20N Service Manual page 92

Section 4 • Repair Procedures
MANIFOLDS
How to Test a Coil Diode
Genie incorporates spike suppressing diodes in all
of its valve coils. 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. See How to Test a
Coil.
2 Connect a 10Ω 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.
Resistor, 10Ω Ω Ω Ω Ω
Genie part number
4 - 42
27287
Z-30/20N • Z-30/20N RJ • Z-34/22 • Z-34/22N
COIL
d
c
W
10
RESISTOR
c
a multimeter
b 9V DC battery
c 10Ω resistor
d coil
Note: Dotted lines in illustration indicate a
reversed connection as specified in
step 6
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.
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 amperage 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.
June 2011
REV B
MULTI
METER
-
9V
BATTERY
-
Part No. 139378
a
b
b