Motor Is Hot And Runs Intermittently; Electrical Short - Graco ultra 750 Instruction Manual

MOTOR IS HOT AND RUNS INTERMITTENTLY

TYPE OF PROBLEM

ELECTRICAL SHORT

TYPE OF PROBLEM
Building circuit breaker opens
as soon as sprayer switch is
turned on.
CAUTION
Any short in any part of the
motor power circuit, which is
connected to the output side
of the bridge, will cause the
bridge to burn out immedi-
ately. Correctly diagnose and
repair all shorts before check-
ing and replacing bridge.
Building circuit breaker
opens as soon as
sprayer is plugged into
outlet and sprayer is
NOT turned on.
Sprayer circuit breaker opens
after sprayer operates for 5 to
10 minutes.
.
WHAT TO CHECK
If check is OK, go to next check
1. Determine if sprayer was operated at high
pressure with small tips, which causes low
motor RPM and excessive heat build up.
2. Be sure ambient temperature where sprayer
is located is no more than 90 F and sprayer
is not located in direct sun.
3. Determine if was sprayer turned on, pressur-
ized, but not operating for long periods of time.
WHAT TO CHECK
If check is OK, go to next check
1. Check all electrical wiring for damaged insula-
tion, and all terminals for loose fit or damage.
Also check wires between pressure control
and motor which are encased in conduit (1).
See page 34.
2. Check for missing inspection plate gasket
(see page 25), bent terminal forks or other
metal to metal contact points which could
cause a short.
3. Check motor armature for shorts. Use an ar-
mature tester (growler) or perform spin test.
See page 22. Inspect windings for burns.
4. Check bridge (308) by substituting with a
good bridge or by performing bridge test. See
page 24.
CAUTION: Do not check bridge until arma-
ture is determined to be good. A bad armature
will immediately burn out a good bridge.
1. Check 'Basic Electrical Problems' on page
16.
2. Check ON/OFF switch (302) See page 26. Be
sure the sprayer is unplugged! Disconnect
wires from switch. Check switch with ohmme-
ter. The reading should be infinity with the ON/
OFF switch OFF, and zero with the switch ON.
CAUTION: A short in the motor circuit burns
the bridge out immediately , which usually
causes the ON/OFF switch to fail in the closed
mode.
1. Check electrical supply with volt meter. Meter
should read 105 to 125 VAC.
2. Check tightness of pump packing nut. Over-
tightening tightens packings on rod, restricts
pump action, and damages packings.
3. Check maximum working pressure adjust-
ment.
4. After determining that there is no short in sys-
tem, reset circuit breaker button.
WHAT TO DO
When check is not OK refer to this column
1. Decrease pressure setting or increase tip
size.
2. Move sprayer to shaded, cooler area if pos-
sible.
3 Turn off sprayer whenever you stop spray-
ing for a while and relieve fluid pressure.
WHAT TO DO
When check is not OK refer to this column
1. Repair or replace any damaged wiring or
terminals. Securely reconnect all wires.
2. Correct faulty conditions.
3. Replace motor. See page 34.
4. Replace bridge. See page 27.
2. Replace ON/OFF switch. See page 26.
1. If voltage is too high, do not operate
sprayer until corrected.
2. Loosen packing nut. Check for leaking
around throat. Replace pump packings, if
necessary. See page 37.
3. Perform pressure control adjustment. See
page 30.
4. If circuit breaker continues to open (button
pops up), replace the circuit breaker. See
page 27.
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