Genie TMZ-50/30 Service Manual page 120

Section 4 • Repair Procedures
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MANIFOLDS
How to Test a Coil Diode
Genie incorporates spike suppressing diodes in all
of its 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 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 9-13, 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.
The battery should read 9V DC or
more when measured across the
terminals.
Resistor, 10W
Genie part number
3 Set a multimeter to read DC amperage.
The multimeter, when set to read
DC amperage, should be capable
of reading up to 800 mA.
4 Connect the negative lead to the other terminal
on the coil.
If testing a single-terminal coil,
connect the negative lead to the
internal metallic ring at either end
of the coil.
4 - 66
COIL
d
c
10
RESISTOR
c
5 Momentarily connect the positive lead from the
multimeter to the positive terminal on the 9V
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
27287
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.
TMZ-50/30
June 2005
MULTI
METER
-
W
9V
BATTERY
-
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
Part No. 65162
REV B
a
b
b