Quietpact 40G Diagnostic Repair Manual Model 4700 - Generac Parts

Section 2
Major Generator Components
Breather Assembly
VOLTAGE
ADjUST POT
11S 22S
4
Ok
6
2A
DESCRIPTION:
A crankcase breather is located in the rocker arm
cover of horizontal crankshaft engines (Figure 2-8).
The breather serves to maintain a reduced pressure
in the engine crankcase, to prevent oil from being
forced past the oil seals, gaskets or piston rings.
The CHECK VALVE allows excess pressure to be
vented out of the crankcase and to atmosphere
through the BREATHER TUBE. Two small DRAIN
HOLES allow condensed oil vapors to return to the
crankcase.
LED
CHECK
VALVE
Figure 2-7. – Voltage Regulator
The regulator mounts a “VOLTAGE ADJUST” potentiometer,
used for adjustment of the pre-set
REFERENCE voltage. A lamp (LED) will turn on to
indicate that SENSING voltage is available to the regulator
and the regulator is turned on.
The regulator mounts a “VOLTAGE ADJUST” potentiometer,
used for adjustment of the pre-set
REFERENCE voltage. A lamp (LED) will turn on to
indicate that SENSING voltage is available to the regulator
and that the regulator is turned on.
ROCKER
ARM
COVER
DRAIN HOLE
BREATHER
TUBE
Voltage ADJUSTMENT PROCEDURE:
With the frequency set at 62.5 Hertz and no load on
the generator, slowly turn the voltage adjust pot on the
voltage regulator until 124 VAC is measured. If voltage
is not adjustable, proceed to Section 6 -
Troubleshooting; Problem 2.
NOTE: If, for any reason, sensing voltage to the
regulator is lost, the regulator will shut down and
excitation output to the Rotor will be lost. The AC
output voltage will then drop to a value that is
commensurate with Rotor residual magnetism
(about 7-12 VAC). Without this automatic shutdown
feature, loss of sensing (actual) voltage to the regulator
would result in a “full field” or “full excitation”
condition and an extremely high AC output
voltage.
NOTE: Adjustment of the regulator’s “VOLTAGE
ADJUST” potentiometer must be done only when
the unit is running at its correct governed no-load
speed. Speed is correct when the unit’s no-load
AC output frequency is about 62.5 Hertz. At the
stated frequency, AC output voltage should be
about 124 volts.
Figure 2-8. – Crankcase Breather
INSPECTION:
1. Remove the breather tube. Check tube for cracks, hardening or
other damage. Replace if necessary.
2. Clean the rocker arm cover in commercial solvent.
3. Make sure the two small drain holes are open. If necessary, use
a length of wire to open the holes.
4. Check the rivets that retain the check valve, make sure they are
tight.
5. The breather plate is retained in the rocker arm cover with a
continuous bead of Type 103 black RTV sealant. This sealant
must not leak. Test the sealant for leakage as follows:
a. Seal all holes on the breather plate.
b. Apply air pressure of 5 psi (0.352 kg/cm ) through
the breather hose hole. No leakage must be
observed.
c. If necessary, reseal the plate with Type 103 black
RTV sealant.
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