Onan MJA Series Service Manual page 122

120 CONTROL SYSTEM
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6.1 MAINTENANCE
Periodically check all connections and contacts in the control system.
Blowout accumulated dust with low pressure air. The breaker point
gap of the engine mounted centrifugal switch will have to be checked at
regular intervals, see periodic service chart. Tills gap should be set
at .020".
NOTE: This switch is not used on :MJA and 5MJB models except with
optional low oil pressure cut-off. Revolving field plants use
the switch to disconnect the starter and as a time delay device
with optional low oil pressure cut-off.
Because of the basic differences between the control system for MJA,
5MJB (Prior Spec F), and 5MJB (Begin Spec F) models and the control
system for 705MJB and. MJC models, they will be discussed separately.
6.2 TESTING AND REPAIR
MODELS: REVOLVING ARMATURE MODELS 5M.JB-R (Prior to Spec
F) and MJA-R
These generating plants use the gen:erator as a starting motor. The
control system includes the starting circuit, a battery charging circuit
with reverse current relay and optional high temperature and low oil
pressure cut-offs.
MODELS: REVOLVING ARMA TORE MODELS 5M.JB-R (Begin Spec F)
These generating plants use a separate automotive type starting motor.
The control system includes
the
starting circuit, a battery charging cir­
cuit with reverse current relay and optional high temperature and low
oil pressure cut-offs.
. If
any component of the control sys­
tem fails, replace
it.
Normally, it
isn't worthwhile to attempt repairs
on individual relays, etc.
6.2.1 STARTING AND STOPPING ­
The starting system for these mod ­
els includes the start solenoid, stop
relay, and start-disconnect relay
(MJB only). Fig. 6. A shows a start ­
ing cycle. To stop the engine, the
stop switch grounds
the
stop relay,
breaking the ignition coil circuit.
(EARLY STYLE)
FIG 6. B - OVERTIGHTENED START
SOLENOID CONNECTIONS