Graco ST Setup guide

309710
Rev. C
First choice when
quality counts.
REPAIR
INSTRUCTIONS
KEEP FOR REFERENCE.
Read this and all related manuals for
important warnings and instructions.
STSTX
Airless Paint Sprayers
3000 psi (207 bar, 20.7 MPa ) Maximum Working Pressure
120 Vac
234127, A, B
234126, A, B
110 Vac UK
234187, A, B
220–240 Vac
234175, A, B
234177, A, B
234179, A, B
246993, A, B
Table of Contents
Component Function and Identification 3. . . . . . . . . . . .
Grounding 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Repair Information 4. . . . . . . . . . . . . . . . . . . . . .
Spin Test 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Motor Brush Replacement 10. . . . . . . . . . . . . . . . . . . . .
On/Off Switch Replacement 12. . . . . . . . . . . . . . . . . . . .
Pressure Control Repair 16. . . . . . . . . . . . . . . . . . . . . . .
Drive Housing Replacement 19. . . . . . . . . . . . . . . . . . . .
Motor Replacement 20. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Displacement Pump Replacement 21. . . . . . . . . . . . . . .
Technical Data 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Graco Phone Number 22. . . . . . . . . . . . . . . . . . . . . . . . . .
Graco Warranty 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GRACO INC. P.O. BOX 1441 MINNEAPOLIS, MN 55440–1441
COPYRIGHT 2002, GRACO INC.
Graco Inc. is registered to I.S. EN ISO 9001
234127
309639; STX. . . . . . .
309053; STX. . . . . . .
Related manuals
309719; Asia. . . . . . .
309665. . . . . . .
309045; ST North America. . . . . . .
309718; Europe. . . . . . .
309060; ST. . . . . . .
309715; North America. . . . . . .
309097; ST Europe. . . . . . .
ti5875a

2309710
The following are general Warnings related to the safe setup, use, maintenance and repair of this equipment.
Additional, more specific warnings may be found throughout the text of this manual where applicable.
WARNING
FIRE AND EXPLOSION HAZARD
Flammable fumes, such as solvent and paint fumes, in work area can ignite or explode. To help
prevent fire and explosion:
Use equipment only in well ventilated area.
Eliminate all ignition sources; such as pilot lights, cigarettes, portable electric lamps, and plastic
drop clothes (potential static arc).
Keep work area free of debris, including solvent, rags and gasoline.
Do not plug or unplug power cords or turn lights on or off when flammable fumes are present.
Ground equipment and conductive objects in work area. Read Grounding instructions.
If there is static sparking or you feel a shock, stop operating immediately. Do not use equipment
until you identify and correct the problem.
INJECTION HAZARD
High pressure fluid from gun, hose leaks, or ruptured components will pierce skin. This may look like
just a cut, but it is a serious injury that can result in amputation. Get immediate medical attention.
Do not point gun at anyone or any part of the body.
Do not put your hand over the spray tip.
Do not stop or deflect leaks with your hand, body, glove, or rag.
Do not spray without tip guard and trigger guard installed.
Engage trigger lock when not spraying.
Follow Pressure Relief Procedure in this manual, when you stop spraying and before cleaning,
checking or servicing equipment.
INSTRUCTIONS
EQUIPMENT MISUSE HAZARD
Misuse can cause death or serious injury.
Do not exceed the maximum working pressure or temperature rating of the lowest rated system
component. Read Technical Data in all equipment manuals.
Use fluids and solvents that are compatible with equipment wetted parts. Read Technical Data in
all equipment manuals. Read fluid and solvent manufacturer’s warnings.
Check equipment daily. Repair or replace worn or damaged parts immediately.
Do not alter or modify equipment.
Use equipment only for its intended purpose. Call your Graco distributor for information.
Route hoses and cables away from traffic areas, sharp edges, moving parts and hot surfaces.
Do not use hoses to pull equipment.
Keep children and animals away from work area.
Comply with all applicable safety regulations.
PRESSURIZED ALUMINUM PARTS HAZARD
Do not use 1,1,1-trichloroethane, methylene chloride, other halogenated hydrocarbon solvents or
fluids containing such solvents in this equipment. Such use could result in a serious chemical reaction,
with the possibility of explosion, which could cause death, serious injury and/or substantial property
damage.

3309710
Component Identification and Function
K
E
H
B
A
D
J
G
F
V
U
N
M
PR T S
ti5914a
AMotor DC motor, permanent magnet, fan cooled
BDrive Assembly Transfers power from DC motor to displacement pump
DDisplacement Pump Transfers fluid to be sprayed from source through spray gun
EFluid Outlet Spray gun is connected here
FPrime Valve Used to prime and drain sprayer (also relieves fluid outlet pressure) when
open
GFluid Filter (optional) Final filter of fluid to spray gun
HPressure Adjusting Knob Controls fluid outlet pressure
JPressure Control Controls motor speed to maintain fluid outlet pressure at displacement pump
outlet. Works with pressure adjusting knob.
KON/OFF Switch Power switch that controls main power to sprayer
M50 ft (15 m) Main Hose 1/4 in. ID, grounded, nylon hose with spring guards on both ends
NSpray Gun High pressure spray gun with gun safety latch
PRAC IV Switch Tip Uses high pressure fluid to clear tip clogs without removing tip from spray gun
RTip Guard Tip guard reduces risk of injection injury
SThumb Lock Safety Gun safety latch inhibits accidental triggering of spray gun
TPower Cord Rack Holds wrapped power cord for storage
USuction Hose Transfers fluid to be sprayed from source to pump
VDrain Tube Fluid outlet used to drain and prime the sprayer

4309710
General Repair Information
Pressure Relief Procedure
WARNING
INJECTION HAZARD
System pressure must be manually
relieved to prevent system from starting
or spraying accidentally. Fluid under high
pressure can be injected through skin and cause
serious injury. To reduce risk of injury from injec-
tion, splashing fluid, or moving parts, follow Pres-
sure Relief Procedure whenever you:
are instructed to relieve pressure,
stop spraying,
check or service any system equipment,
or install or clean spray tip.
1. Lock gun safety latch.
2. Turn ON/OFF switch to OFF.
3. Unplug power supply cord.
4. Unlock gun safety latch. Hold metal part of gun
firmly to grounded metal pail. Trigger gun to relieve
pressure.
5. Lock gun safety latch.
6. Open pressure drain valve. Leave pressure drain
valve open until ready to spray again.
If suspected that spray tip or hose is completely
clogged, or that pressure has not been fully relieved
after following steps above, VERY SLOWLY loosen tip
guard retaining nut or hose end coupling to relieve
pressure gradually, then loosen completely. Now clear
tip or hose obstruction.
CAUTION
To reduce risk of pressure control malfunction:
Use needle nose pliers to disconnect wire. Never
pull on wire, pull on connector.
Mate wire connectors properly. Center flat blade of
insulated male connector in female connector.
Route wires carefully to avoid interference with
other connections of pressure control. Do not pinch
wires between cover and control box.
1. Keep all screws, nuts, washers, gaskets, and
electrical fittings removed during repair proce-
dures. These parts are not normally provided with
replacement assemblies.
WARNING
ELECTRIC SHOCK HAZARD
MOVING PARTS HAZARD
To reduce risk of serious injury, including
electric shock, do not touch moving or
electrical parts with fingers or tools while
testing repair. Shut off and unplug spray-
er when inspection is complete. Install all
covers, gaskets, screws and washers
before operating sprayer.
2. Test repair after problem is corrected.
3. If sprayer does not operate properly, review
repair procedure to verify procedure was done
correctly. If necessary, see Troubleshooting Guide,
pages 5 – 9, for other possible solutions.
WARNING
HOT SURFACES HAZARD
EXPLOSION HAZARD
Motor and drive housing may be very hot
during operation and could burn skin if
touched.
Flammable materials spilled on hot, bare
motor could cause fire or explosion.
Have motor shroud in place during
operation to reduce risk of burns, fire or
explosion.
CAUTION
Do not run sprayer dry for more than 30 seconds to
avoid damaging pump packings.
4. Install motor shroud before operation of spray-
er and replace if damaged. Motor shroud prevents
overheating, and protects operator from possible
electrical shock by touching terminals of capacitor.
It can also reduce risk of burns, fire or explosion;
see preceding WARNING.

5309710
Grounding
WARNING
Improper installation or alteration of grounding plug
results in risk of electric shock, fire or explosion
that could cause serious injury or death.
1. 220–240 Vac models require a 50 Hz, 10A circuit
with a grounding receptacle. 100–120 Vac models
require a 50/60 Hz, 15A circuit with a grounding
receptacle. See Fig. 1.
2. Do not alter ground prong or use adapter.
Fig. 1
Grounding Plug Grounded
Outlets
240 Vac model shown
3. 120 Vac: A 12 AWG, 3 wires with grounding prong,
300 ft (90 m) extension cord may be used.
220–240 Vac: You may use a 3-wire, 1.0 mm (12
AWG) (minimum) extension cord up to 90 m long.
Long lengths reduce sprayer performance.
Troubleshooting
Relieve pressure;page 4.
MOTOR WON’T OPERATE
TYPE OF PROBLEM WHAT TO CHECK
If check is OK, go to next check
WHAT TO DO
When check is not OK refer to this column
Basic Fluid Pressure
Problems
1. Pressure control knob setting. Motor will not run
if at minimum setting (fully counterclockwise).
1. Slowly increase pressure setting to see if mo-
tor starts.
2. Spray tip or fluid filter may be clogged. 2. Relieve pressure and clear clog or clean fil-
ter; refer to separate gun or tip instruction
manual.
Basic Mechanical
Problems
1. Pump (13) for frozen or hardened paint. 1. Thaw sprayer if water or water-based paint
has frozen in sprayer. Place sprayer in warm
area to thaw. Do not start sprayer until
thawed completely. If paint hardened (dried)
in sprayer, replace pump packings. See
page 21 (Displacement Pump Replace-
ment).
2. Displacement pump connecting rod pin (9a).
Pin must be completely pushed into connecting
rod (9) and retaining spring (9b) must be firmly
in groove of pump pin. See Fig. 10.
2. Push pin into place and secure with spring re-
tainer.
3. Motor (1). Remove drive housing assembly
(10). See page 19. Try to rotate fan by hand.
3. Replace motor (1) if fan won’t turn. See page
20.
Basic Electrical Problems 1. Motor control board. Board shuts down and dis-
plays error code.
1. See Motor Control Board Diagnostics,
page 16.
2. Electrical supply. Meter must read:
210–255 Vac for 220–240 Vac models.
85–130 Vac for 100–120 Vac models.
2. Reset building circuit breaker; replace build-
ing fuse. Try another outlet.
3. Extension cord. Check extension cord continu-
ity with volt meter.
3. Replace extension cord.
4. Sprayer power supply cord (79). Inspect for
damage such as broken insulation or wires.
4. Replace power supply cord.

6309710
Troubleshooting
MOTOR WON’T OPERATE (Continued)
TYPE OF PROBLEM WHAT TO CHECK
If check is OK, go to next check
WHAT TO DO
When check is not OK refer to this column
Basic Electrical Problems
(continued)
5. That motor leads are securely fastened and
properly mated.
5. Replace loose terminals; crimp to leads. Be
sure terminals are firmly connected.
Clean circuit board terminals. Securely re-
connect leads.
6. For loose motor brush lead connections and ter-
minals. See page 10.
6. Tighten terminal screws. Replace brushes if
leads are damaged. See page 10.
7. Brush length which must be 1/2 in. minimum.
See page 10.
NOTE: Brushes do not wear at the same rate on
both sides of motor. Check both brushes.
7. Replace brushes. See page 10.
8. For broken or misaligned motor brush springs.
Rolled portion of spring must rest squarely on
top of brush. See page 10.
8. Replace spring if broken. Realign spring with
brush. See page 10.
9. Motor brushes may be binding in brush holders.
See page 10.
9. Clean brush holders. Remove carbon with
small cleaning brush. Align brush leads with
slot in brush holder to assure free vertical
brush movement.
10.Motor armature commutator for burn spots,
gouges and extreme roughness.
See page 10.
10.Remove motor and have motor shop resur-
face commutator if possible. See page 20.
11. Motor armature for shorts using armature tester
(growler) or perform spin test. See page 10.
11.Replace motor. See page 20.
Refer to wiring diagram on
page 13, 14 or 15 to identify
test points (TP).
1. Power supply cord (79). Connect volt meter be-
tween TP1 (neutral) and TP2 (L2, 120 Vac).
Plug in sprayer. Meter must read:
210–255 Vac for 220–240 Vac models.
85–130 Vac for 100–120 Vac models.
Unplug sprayer.
1. Replace power supply cord.
2. ON/OFF switch (23). Connect volt meter be-
tween L1 or L and L2 or N terminal on ON/OFF
switch. Plug in sprayer and turn ON.
Meter must read:
210–255 Vac for 220–240 Vac models.
85–130 Vac for 100–120 Vac models.
2. Replace ON/OFF switch. See page 12.
3. Motor thermal cutoff switch. Turn sprayer OFF.
Check for continuity between TO1 and TO2 with
ohmmeter.
3. If thermal switch is open (no continuity), allow
motor to cool. If switch remains open after
motor cools, replace motor. If thermal switch
closes after motor cools, correct cause of
overheating.
4. All terminals for damage or loose fit. 4. Replace damaged terminals and reconnect
securely.

7309710
Troubleshooting
LOW OR FLUCTUATING OUTPUT
TYPE OF PROBLEM WHAT TO CHECK
If check is OK, go to next check
WHAT TO DO
When check is not OK refer to this column
Low Output 1. For worn spray tip. 1. Follow Pressure Relief Procedure Warn-
ing, then replace tip. See your separate
gun or tip manual.
2. Verify pump does not continue to stroke when
gun trigger is released.
2. Service pump. See page 21.
3. Filter clogged (If optional filter is installed). 3. Relieve pressure. Check and clean filter.
4. Prime valve leaking. 4. Relieve pressure. Repair prime valve.
5. Suction hose connections. 5. Tighten any loose connections.
6. Electrical supply with volt meter.
Meter must read:
210–255 Vac for 220–240 Vac models.
85–130 Vac for 100–120 Vac models. Low volt-
ages reduce sprayer performance.
6. Reset building circuit breaker; replace
building fuse. Repair electrical outlet or try
another outlet.
7. Extension cord size and length; must be at least
12 gauge wire and no longer than 300 ft. Longer
cord lengths reduce sprayer performance.
7. Replace with a correct, grounded exten-
sion cord.
8. Leads from motor to pressure control circuit
board (35) for damaged or loose wires or con-
nectors. Inspect wiring insulation and terminals
for signs of overheating.
8. Be sure male terminal blades are centered
and firmly connected to female terminals.
Replace any loose terminal or damaged
wiring. Securely reconnect terminals.
9. For loose motor brush leads and terminals. See
page 10.
9. Tighten terminal screws. Replace brushes
if leads are damaged. See page 10.
10.For worn motor brushes which must be 1/2 in.
minimum. See page 10.
10. Replace brushes. See page 10.
11. For broken and misaligned motor brush
springs. Rolled portion of spring must rest
squarely on top of brush.
11. Replace spring if broken. Realign spring
with brush. See page 10.
12.Motor brushes for binding in brush holders. See
page 10.
12.Clean brush holders, remove carbon dust
with small cleaning brush. Align brush lead
with slot in brush holder to assure free verti-
cal brush movement.
13.Low stall pressure. 13. Do either or both:
a. Turn pressure control knob fully
clockwise. Make sure pressure
control knob is properly installed
to allow full clockwise position.
b. Try a new transducer.
14.Motor armature for shorts by using an armature
tester (growler) or perform spin test. See page
10.
14.Replace motor. See page 20.

8309710
Troubleshooting
LOW OR FLUCTUATING OUTPUT
TYPE OF PROBLEM WHAT TO CHECK
If check is OK, go to next check
WHAT TO DO
When check is not OK refer to this column
Motor runs and pump strokes 1. Paint supply. 1. Refill and reprime pump.
2. Intake strainer clogged. 2. Remove and clean, then reinstall.
3. Suction tube or fittings loose. 3. Tighten; use thread sealant or sealing tape
on threads if necessary.
4. To see if intake valve ball and piston ball are
seating properly. See page 21.
4. Remove intake valve and clean. Check
balls and seats for nicks; replace if neces-
sary, page 21. Strain paint before using to
remove particles that could clog pump.
5. Leaking around throat packing nut which may
indicate worn or damaged packings. See
page 21.
5. Replace packings, page 21. Also check
piston valve seat for hardened paint or
nicks and replace if necessary. Tighten
packing nut/wet-cup.
6. Pump rod damage. 6. Repair pump, page 21.
7. Capacitor failure. Visually inspect capacitor
near terminals. Ensure that orange safety re-
lief plug is intact.
7. Replace capacitor.
Motor runs but pump does not
stroke
1. Displacement pump pin (9a) (damaged or
missing), page 21.
1. Replace pump pin if missing. Be sure re-
tainer spring (9b) is fully in groove all
around connecting rod, page 21.
2. Connecting rod assembly (9) for damage,
page 19.
2. Replace connecting rod assembly,
page 19.
3. Gears or drive housing, page 19. 3. Inspect drive housing assembly and gears
for damage and replace if necessary,
page 19.

9309710
Troubleshooting
MOTOR IS HOT AND RUNS INTERMITTENTLY
TYPE OF PROBLEM WHAT TO CHECK
If check is OK, go to next check
WHAT TO DO
When check is not OK refer to this column
Motor is hot and runs intermit-
tently.
1. Determine if sprayer was operated at high
pressure with small tips, which causes low
motor RPM and excessive heat build up.
1. Decrease pressure setting or increase tip
size.
2. Be sure ambient temperature where sprayer
is located is no more than 90F and sprayer
is not located in direct sun.
2. Move sprayer to shaded, cooler area if pos-
sible.
ELECTRICAL SHORT
TYPE OF PROBLEM WHAT TO CHECK
If check is OK, go to next check
WHAT TO DO
When check is not OK refer to this column
Building circuit breaker opens
as soon as sprayer switch is
turned on.
1. All electrical wiring for damaged insulation, and
all terminals for loose fit or damage. Also wires
between pressure control and motor. See page
20.
1. Repair or replace any damaged wiring or
terminals. Securely reconnect all wires.
2. For missing inspection plate gasket (see page
20), bent terminal forks or other metal to metal
contact points which could cause a short.
2. Correct faulty conditions.
3. Motor armature for shorts. Use an armature
tester (growler) or perform spin test. See page
10. Inspect windings for burns.
3. Replace motor. See page 20.
4. Motor control board (35) by performing motor
control board diagnostics on page 16. If diag-
nostics indicate, substitute with a good board.
CAUTION: Do not perform this check until mo-
tor armature is determined to be good. A bad
motor armature can burn out a good board.
4. Replace with a new pressure control board
(35). See page 16.
1. Basic Electrical Problems on page 5. 1. Perform necessary procedures.
2. ON/OFF switch (23) See page 12. Be sure
sprayer is unplugged! Disconnect wires from
switch. Check switch with ohmmeter. Reading
must be infinity with ON/OFF switch OFF, and
zero with switch ON.
2. Replace ON/OFF switch. See page 12.
3. For damaged or pinched wires in pressure con-
trol. See page 16.
3. Replace damaged parts. See page 16.
Sprayer quits after sprayer op-
erates for 5 to 10 minutes.
1. Basic Electrical Problems on page 5. 1. Perform necessary procedures.
2. Electrical supply with volt meter.
Meter must read:
210–255 Vac for 220–240 Vac models.
85–130 Vac for 100–120 Vac models.
2. If voltage is too high, do not operate
sprayer until corrected.
3. Tightness of pump packing nut. Over tightening
tightens packings on rod, restricts pump action,
and damages packings.
3. Loosen packing nut. Check for leaking
around throat. Replace pump packings, if
necessary. See page 21.
.
CAUTION
Any short in any part of the
motor power circuit will cause
the control circuit to inhibit
sprayer operation. Correctly
diagnose and repair all shorts
before checking and replac-
ing control board.
Building circuit breaker opens
as soon as sprayer is plugged
into outlet and sprayer is NOT
turned on.

10 309710
Spin Test
Setup
Electric Shock Hazard; page 4.
To check armature, motor winding and brush electrical
continuity:
1. Relieve pressure;page 4.
2. Remove drive housing; page 19.
3. Fig. 2. Remove pressure control cover (39). Dis-
connect motor leads (F) and (G).
4. Fig. 3. Remove motor shroud (74).
Armature Short Circuit Test
Quickly turn motor fan by hand. If no electrical shorts,
motor coasts two or three revolutions before complete
stop. If motor does not spin freely, armature is
shorted. Replace motor; page 20.
Armature, Brushes, and Motor Wiring Open
Circuit Test (Continuity)
1. Connect red and black motor leads together with
test lead. Turn motor fan by hand at about two
revolutions per second.
2. If uneven or no resistance, check for: broken brush
springs, brush leads, motor leads; loose brush
terminal screws, motor lead terminals; worn
brushes. Repair as needed; page 10.
3. If still uneven or no resistance, replace motor;
page 20.
9578A
Fig. 2
F
G
39
Motor Brush Replacement
Motor Brush Removal
Replace brushes worn to less than 1/2 in. Check both
sides. Brush Repair Kit 243215.
1. Read General Repair Information; page 4.
2. Relieve pressure;page 4.
3. Fig. 3. Remove four screws (18) and motor
shroud (74).
4. Pry off two brush caps (A). Tag locations of red (+)
and black (–) motor leads.
5. Fig. 5. Remove screw (C) and discard brush (B)
for motor with capacitor attached. Remove brush
lead from control box for motor without capacitor
attached.
(Continued on page 11)
TI0053
A
74
Fig. 3
18