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3. Troubleshooting and System Detailed Diagnosis For Johnson Direct Spark Ignition Module P/N 128935
When the dryer calls for heat, 24 VAC from the step down transformer is applied to the TH and GND
terminals of the DSI module. The DSI module L.E.D. (light emitting diode) indicator will LIGHT GREEN.
The gas valve will be energized, and the spark burst will be evident (on) for approximately 8-seconds at the
tip of the electrode flame-probe assembly. Flame should now be established and confirmed. If a flame is
not sensed and confirmed by the ignitor/flame-probe sensor after the approximate 8-second spark burst, the
DSI module will wait 30-seconds and start ALL over again.
If a flame has been established and confirmed and then lost, the DSI module L.E.D. indicator will continue
to LIGHT GREEN, wait 30-seconds and try again. The flame should now be established and confirmed.
If a flame is not sensed and confirmed by the ignitor/flame-probe sensor after the initial try, the module will
try two (2) more times, then if flame is still not established it will go into LOCKOUT mode (the L.E.D. [light
emitting diode] will BLINK GREEN CONTINUOUSLY).
a. System Diagnosis
1) Gas Pressure
A gas pressure test should be taken at the
gas valve pressure tap provided on every gas
valve to assure that the water column (W.C.)
pressure is correct and consistent.
There are two (2) types of devices commonly
used to measure water column (W.C.)
pressure. They are the spring and mechanical
type gauge and the water column test gauge
(manometers). The use of the spring and
mechanical type gauges
is not recommended
because they are not always accurate. The
preferred type of gauge is the manometer
because it is a simple device to use and is
highly accurate. A manometer is simply a
glass or transparent plastic tube with a scale
graduated in inches. When it is filled with
water and pressure is applied, the water in
the inner tube lowers, showing the exact
water column (W.C.) pressure in inches.
WARNING: Test ALL connections for leaks by
brushing on a soapy water solution.
WARNING: NEVER TEST FOR LEAKS
WITH A FLAME!!!