Takeuchi Hydraulic Excavator TB175W (S/N 17540001~). WORKSHOP MANUAL - page 8

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Repair Procedure:

Check for leaks with your leak detector. If you find a

leak at a connection, tighten it then add refrigerant as
necessary. If a component or line is leaking (defective),
recover all refrigerant from the system. Replace the de-
fective part and then check the compressor oil level and
replace missing oil. Evacuate and recharge with refrig-
erant, then check AC operation and performance.

Extremely Low Refrigerant Charge in the System

Tip:

The sight glass is clear or shows oil streaks. The air
from vents in the cab seems warm. If there is a low
pressure or Trinary™ switch in the system it may have
shut off the compressor (clutch).

Cause:

Extremely low or no refrigerant in the system. There is
a leak in the system.

Repair Procedure:

Add refrigerant to the system, at least half of the normal
full charge amount. Then perform your leak test. As an
alternative to a refrigerant, add dry nitrogen gas to the
system and then test for leaks.

Note:

It may be necessary to use a jumper wire to bypass
some types of low pressure cutout switches to operate
the compressor (clutch) when you add refrigerant to
the system.

Manifold Gauge Set Readings

Figure 8-6

Gauge reading, extremely
low refrigerant charge in
system.

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After finding a leak, recover all refrigerant from the

system and repair the leak. Check the compressor and
replace any refrigeration oil lost due to leakage. Evacu-
ate and recharge the system with refrigerant, then check
AC operation and performance.

Air and/or Moisture in the System

Tip:

The  sight  glass  may  be  clear  or  show  some  bubbles.
The air from vents in the cab is only slightly cool. In a
cycling  clutch  type  system  with  a  thermostatic  switch,
the  switch  may  not  cycle  the  clutch  on  and  off,  so  the

low pressure gauge will not fluctuate.

Cause:

Air and/or moisture in the system.

RepairProcedure:

Test  for  leaks,  especially  around  the  compressor  shaft
seal  area.  When  the  leak  is  found,  recover  refrigerant
from the system and repair the leak. Replace the receiv-
er-drier  or  accumulator  because  the  desiccant  may  be
saturated with moisture (there is no way to tell). Check
the  compressor  and  replace  any  refrigeration  oil  lost
due to leakage. Evacuate and recharge the system with
refrigerant, then check AC operation and performance.

Troubleshooting & Service Procedures

Figure 8-7

Gauge reading, air and/or
moisture in the system.

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Excessive Air and/or Moisture in the System

Tip:

There may be occasional bubbles in the sight glass. Air
from vents in the cab is only slightly cool.

Cause:

System contains excessive air and/or moisture.

Repair Procedure:

Test for leaks, recover refrigerant from the system and
repair  the  leak.  Depending  on  the  type  of  system,  re-
place  the  receiver-drier  or  accumulator.  The  desiccant
is saturated with moisture. Check and replace any com-
pressor  oil  lost  due  to  leakage.  Evacuate  and  recharge
the system, then check AC operation and performance.

Expansion Valve (TXV) Stuck Closed or Plugged

Tip:

Air from vents in the cab is only slightly cool. The ex-
pansion valve body is frosted or sweating.

Manifold Gauge Set Readings

Figure 8-9

Gauge reading, expansion
valve (TXV) stuck closed.

Figure 8-8

Gauge reading, excessive
air and/or moisture in the
system.

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Cause:

An expansion valve malfunction could mean the

valve is stuck in the closed position, the filter screen

is clogged (block type expansion valves do not have

filter screens), moisture in the system has frozen at the

expansion valve orifice, or the sensing bulb is not oper

ating. In vehicles where the TXV and sensing bulb are
accessible, perform the following test. If not accessible,
then proceed to

Repair Procedure.

Test:

1. Warm diaphragm and valve body in your hand or

carefully with a heat gun. Activate system and watch
to see if the low pressure gauge rises.

2. Next, carefully spray a little nitrogen, or any sub-

stance below 32 degrees Fahrenheit, on the capillary

coil (bulb) or valve diaphragm. The low side gauge
needle should drop and read at a lower (suction)
pressure on the gauge. This indicates the valve was
part way open and that your action closed it. Repeat

the test, but first warm the valve diaphragm or cap

illary with your hand. If the low side gauge drops
again, the valve is not stuck.

3. Clean the surfaces of the evaporator outlet and the

capillary coil or bulb. Make sure the coil or bulb is

securely clamped to the evaporator outlet tube and
the insulation is in place. Next proceed with recover-
ing refrigerant from the system.

Repair Procedure:

Inspect the expansion valve screen (except block type
valves). To do this you must recover all refrigerant from

the system. Disconnect the inlet hose fitting from the

expansion valve. Remove, clean and replace the screen,
then reconnect the hose. Any signs of contamination
will

require

flushing the system. Next, replace the re

ceiverdrier. Then evacuate and recharge the system with
refrigerant, and check AC operation and performance.

Troubleshooting & Service Procedures

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Note:

If  the  expansion  valve  tests  did  not  cause  the  low
pressure gauge needle to rise and drop, and if the oth-
er  procedures  described  did  not  correct  the  problem,
the  expansion  valve  is  defective.  You  must  recover
all  refrigerant  from  the  system  again,  and  replace
the expansion valve and receiver-drier. Evacuate and
recharge  the  system  with  refrigerant,  then  check AC
operation and performance.

Expansion Valve (TXV) Stuck Open

Tip:

Air from vents in the cab is warm or only slightly cool.

Cause:

The expansion valve is stuck open and/or the capillary
tube (bulb) is not making proper contact with the evap-

orator outlet tube. Liquid refrigerant may be flooding

the  evaporator  making  it  impossible  for  the  refrigerant
to vaporize and absorb heat normally. In vehicles where
the  TXV  and  sensing  bulb  are  accessible,  check  the
capillary tube for proper mounting and contact with the
evaporator outlet tube. Then perform the following test.
If  the  TXV  is  not  accessible,  then  proceed  to  Repair
Procedure.

Test:

1. Operate the AC system on it’s coldest setting for

a few minutes. Carefully spray a little nitrogen or
other cold substance, on to the capillary tube coil (bulb)
or head of the valve.

2. The low pressure (suction) side gauge needle should

now drop on the gauge. This indicates the valve has
closed and is not stuck open. Repeat the test, but

first warm the valve diaphragm with your hand.

Manifold Gauge Set Readings

Figure 8-10

Gauge reading, expansion
valve (TXV) stuck open.

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3. If the low side gauge shows a drop again, the valve

is not stuck. Clean the surfaces of the evaporator

outlet and the capillary coil or bulb. Make sure the

coil or bulb is securely fastened to the evaporator
outlet and covered with insulation material. Operate
the system and check performance.

Repair Procedure:

If the test did not result in proper operation of the ex-
pansion valve, the valve is defective and must be re-
placed. Recover all refrigerant from the system and re-
place the expansion valve and the receiver-drier. Evacu-
ate and recharge the system with refrigerant, then check
AC operation and performance.

System High Pressure Side Restriction

Tip:

Air from vents in the cab is only slightly cool. Look for
sweat or frost on high side hoses and tubing, and frost
appearing right after the point of restriction. The hose
or line may be cool to the touch near the restriction.

Cause:

There could be a kink in a line, or other restriction in
the high side of the system.

Troubleshooting & Service Procedures

Figure 8-11

Gauge reading, system high
pressure side restriction.

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Repair Procedure:

After you locate the defective component containing
the restriction, recover all of the refrigerant. Replace
the defective component and the receiver-drier. Evacu-
ate and recharge the system with refrigerant, then check
AC operation and performance.

Compressor Malfunction

Tip:

The compressor may be noisy when it operates.

Cause:

Defective reed valves or other compressor components.
If the compressor is not noisy, there may be a worn or
loose compressor clutch drive belt.

Repair Procedure:

If you find the belt worn or loose, replace or tighten it

and  recheck  system  performance  and  gauge  readings.
To inspect and service the compressor, you must isolate
(front seat the stem type compressor service valves) and
recover refrigerant, or fully recover R-12 from systems
containing  Schrader  valves.  Remove  the  compressor
cylinder  head  and  check  the  appearance  of  the  reed
valve  plate  assembly.  If  defective,  replace  the  valve
plate and install with new gaskets, or replace the com-
pressor assembly.

Manifold Gauge Set Readings

Figure 8-12

Gauge reading, compressor
malfunction.

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If you find particles of desiccant in the compressor,

remove and replace it and the receiver-drier. Before do-

ing so, back flush other system components (except the

expansion valve) using a flushing kit. If there are stem

type valves and you isolate the compressor, the rest of
the system must be purged of refrigerant before you

can disconnect and flush system components (

Chapter

describes the flushing procedure). After flushing, re

assemble  the  components.  Always  check  the  oil  level
in  the  compressor,  even  if  you  install  a  new  or  rebuilt
unit.  Tighten  all  connections  and  evacuate  the  system.
Recharge the air conditioner with refrigerant and check
system operation and performance.

Note:

Rotary compressors have a limited oil reservoir. Extra
oil must be added for all truck installations

Condenser Malfunction or System Overcharge

Tip:

The  air  from  vents  in  the  cab  may  be  warm.  In  R-12
systems  there  can  be  bubbles  in  the  sight  glass.  The
high  pressure  hoses  and  lines  will  be  very  hot.  Don’
t  forget  to  check  the  engine  cooling  system  compo-
nents—fan and drive belt, fan clutch operation, and the
radiator shutter.

Troubleshooting & Service Procedures

Figure 8-13

Gauge reading, condenser
malfunction or system over-
charge.

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Cause:

The condenser is not functioning correctly or there may
be an overcharge of refrigerant inside the system. An-

other possibility is lack of (ram) air flow through the

condenser fins during testing. Engine cooling system

component malfunction can cause high pressure by

blocking air flow (radiator shutter) or not providing air

flow (fan clutch) in sufficient quantity.

Repair Procedure:

Inspect the condenser for dirt, bugs or other debris and
clean  if  necessary.  Be  sure  the  condenser  is  securely
mounted  and  there  is  adequate  clearance  (about  1-1/2
inches)  between  it  and  the  radiator.  Check  the  radiator
pressure cap and cooling system, including the fan, fan
clutch,  drive  belts  and  radiator  shutter  assembly.  Re-
place  any  defective  parts  and  then  recheck AC  system
operation, gauge readings and performance.

If  the  problem  continues,  the  system  may  be  over-
charged (have too much refrigerant inside). Recover the
system slowly until low and high pressure gauges read
below  normal,  and  bubbles  appear  in  the  sight  glass.
Then add refrigerant (charge the system) until pressures
are  normal  and  the  bubbles  disappear.  Add  another
quarter to half pound of refrigerant and recheck AC sys-
tem operation, gauge readings and performance.

If the high gauge readings do not change, you should

recover all of the refrigerant and flush (it may be par

tially plugged) or replace the condenser. Also replace
the receiver-drier or accumulator. Then connect the
components and evacuate the system. Recharge the air
conditioner with refrigerant and check system operation
and performance.

Manifold Gauge Set Readings

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Thermostatic Switch Malfunction

Tip:

The low side gauge needle may fluctuate in a very nar

row range compared to a normal range. The compressor
clutch may be cycling on and off more frequently than
it should.

The low side gauge needle may fluctuate in an above

normal range as the clutch cycles. This may be an indi-
cation that the thermostat is set too high (someone may
have attempted to adjust the factory setting). A new
thermostat may have been installed incorrectly (capil-

lary tube not inserted between the evaporator fins in the

proper position).

Cause:

The thermostatic switch is not functioning properly or
at all.

Repair Procedure:

Replace the thermostatic switch. When you remove the
old  thermostat,  replace  it  with  one  of  the  same  type.
(They  operate  in  a  factory  preset  temperature  range.)
Take care in removing and handling the thermostat and
thin  capillary  tube  attached  to  it.  Don’t  kink  or  break
the tube.

Position the new thermostat capillary tube at or close to

the same location and seating depth between the evapo-

rator coil fins as the old one. Connect the electrical

leads.

Troubleshooting & Service Procedures

Figure 8-14

Gauge reading, thermostatic
switch malfunction.

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Note:

See the Thermostat section in Chapter 10. Fan clutch,
radiator shutter, condenser, compressor, and the new-
er air and water valve control systems are covered in
Chapter 10.

Review of Frequent Problem Areas

In HVAC systems a limited number of things can go wrong. Moving parts of the

compressor, clutch, and expansion valve or refrigerant metering device can mal-
function or break down from metal fatigue, contamination, abnormal pressure or
lack of lubrication. Electrical connections may corrode, become disconnected or
break. Fuses blow from shorts or overload. Belts slip or break.

Vibration from the engine or road surface can work bolts and air or vacuum

lines loose, or rub and break or wear parts out. Motors may burn out. The inside

of the system can become contaminated from moisture, air or desiccant material

breakdown. Refrigerant may leak out of the system quickly or very slowly. Mois

ture in the system can combine with refrigerant to form acid and attack (corrode)

metal parts from the inside. Moisture and refrigeration oil can combine to form

sludge that may block refrigerant flow.

The following problems are discussed in more detail in this section:

1. Belts and Compressor Clutch

2. Condenser

3. Refrigerant Lines, Hoses, and Fittings

4. Refrigerant Metering Valves

5. Other Problems

1. Belts and Compressor Clutch

Let’s review problem areas listed at the beginning of Chapter 7. The most
frequent repairs are replacing belts and servicing or replacing the compres-
sor or clutch. Heavy duty vehicle operation puts a lot of stress on these parts.
There are several main reasons.

There is often continuous operation for long periods of time. There may

be frequent sudden RPM variations when shifting gears up or down. For

this reason the AC clutches used in heavy duty systems usually have double
row ball bearings. Vibration and road shock contribute to loose or broken

mounting brackets, electrical connections and fittings. Belts, bearings and

compressor reed valves wear out.

Various compressor clutch cutout switches are used because the AC de-

signers know about compressor operating conditions. System leaks, high
operating pressures, malfunctioning engine cooling system components—
all cause compressor problems and failures. When refrigerant and refrigera-

tion oil leaks out of a system or there is contamination blocking oil flow, the

compressor will be starved for oil and seize.

Review of Frequent Problem Areas

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2. Condenser

Condensers get dirty and the dirt reduces heat movement by insulating the

condenser. The fittings come loose or break from stress if the condenser or

connecting hoses are not secured properly to keep the effects of vibration at
a minimum.

Heat transfer efficiency and pressure in the condenser are affected by the

amount of outside air flowing through condenser fins. A lack of air flow can

mean the refrigerant doesn’t give up enough heat energy to the outside air (it
doesn’t change state). The refrigerant arrives at the evaporator as a gas and
can’t pick up any heat energy from cab air. In the cab, air from the vents is
only slightly cool or warm.

One possible cause of condenser malfunction could be the engine cooling

system. This is why fan clutches and radiator shutters are often controlled or
overridden by AC switch function. In fact, we can add fan clutch, radiator
shutters and also fan motors to condenser problems. If they don’t function

to allow sufficient air through the condenser, pressure inside the system may

become dangerously high. A lack of air through the condenser fins can raise

high side pressure and blow out the weakest point in a system, or damage
the compressor.

3. Refrigerant Lines, Hoses and Fittings

Problems with these parts may be caused by normal deterioration, vibration

damage, lack of maintenance or human error (improper installation or re-
placement). All rubber parts are attacked by ozone (oxygen) in the air. Rub-
ber parts break down slowly and become more vulnerable to the effects of
vibration with the passage of time.

Heavy duty vehicle vibration causes stress on all lines, fittings and connec

tions. Regular maintenance includes checking and tightening any suspect
line, or hose retainers, or grommet position where the grommet is protecting
a line or hose from abrasion. Any insulating material wrapped around hoses
must be in place and securely fastened.

4. Refrigerant Metering Valves

When  you  consider  valve  problems  there  are  obvious  differences  in  valve
construction  and  what  can  go  wrong.  If  a  valve  is  clogged  with  sludge  or
other obstruction, the result is a valve problem but the cause is contamina-
tion  in  the  system.  Valves  get  stuck  open  or  closed,  although  most  often
closed  when  the  gas  charge  is  lost  from  the  diaphragm  housing  in  a  tradi-
tional TXV. The capillary tube can vibrate loose from the evaporator outlet
tube. The capillary can break and the small quantity of temperature sensitive
gas can escape. The diagnosis of a valve as defective calls for replacement.

5. Other Problems—Leaks, Moisture, and Adding

Refrigerant

Before any refrigerant was put inside the AC system, someone used a vacu-
um pump to evacuate any air and moisture. Vacuum is really a force pulling

against all hoses, fittings and components from the inside. When the system

is charged with refrigerant, the pressure goes from minus (a vacuum) to plus
pressure inside the hoses and all components. The refrigerant and refrigera-
tion oil are trying to escape from the system at all times.

Troubleshooting & Service Procedures

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Technicians frequently add refrigerant to a system, replacing refrigerant

seepage through system connections or fittings. If the system has been main

tained regularly (every three to six months), adding a small amount of re-
frigerant may result in normal system function. However, the best procedure

is to check all connections and look for, find and repair any leaks before

adding refrigerant.

When your leak detector indicates the presence of a leak, you can’t tell

how long the system has been leaking. Finding one leak doesn’t mean there
are not others. Until you have some AC system work experience, it will be
hard to guess how much refrigerant may have leaked. If you have to top a
system off with a half pound of refrigerant or more, adding refrigerant is not
the answer.

Find the leak. Recover all of the refrigerant and repair the system. The

moisture absorbing capacity of any desiccant material is limited and can-
not be measured. For that reason, replace the receiver-drier or accumulator.
Then evacuate the system for an hour and recharge with refrigerant.

When a compressor shaft seal has leaked oil and the refrigerant charge is

a little low, the shaft seal may have leaked because the air conditioner was
not used. The seal can get a little out of round from the weight of the crank-
shaft and leak above the shaft. Running the compressor may cause the seal
to swell and close up the leak. The shaft rotation exerts force all around the
seal and puts life back into it. To prevent this from happening, manufactur-
ers recommend regular AC system operation a minimum of every couple of
weeks even in cool weather.
Keep in mind that the compressor can cause a vacuum inside the system if
there is a restriction in the system. That means it can suck air and moisture
inside under some conditions. It will pull these contaminants in through the
same space where refrigerant and refrigerant oil has leaked out.

Conclusion

What could the air conditioning problem and it’s cause have been at the begin-
ning of this chapter? The operator was in a hurry, but you were able to start your

troubleshooting with the answers he gave you. Problems your inspection may

have turned up are a very low refrigerant charge, a contaminated system or defec-

tive compressor. Those are not quick fix jobs.

On the other hand, you might have found enough debris on the condenser fin

surface to boost high side pressures to an abnormal level during the hottest part of
the day. So the Trinary™ or high pressure switch would cut out from high pres-
sure—but reset itself. You cleaned the condenser, added a half pound of refriger-
ant and AC system pressures and function returned to normal. Service and repair
took a half hour. But there was no way to tell without using your knowledge and
experience. By now you are pretty familiar with AC system problems, the reasons
for some of them, troubleshooting and repair. In Chapter 9 we will describe com-

plete system purging, evacuation, flushing and recharging.

Conclusion

MACHINE CONFIGURATION

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IV .

HYDRAULIC UNITS

HYDRAULIC UNITS

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CONTENTS

Hydraulic Pump (Piston) ....................................................................................................................................... 3

Hydraulic Pump (Gear) ....................................................................................................................................... 17

Control Valve (Mono-Block) .............................................................................................................................. 25

Control Valves (3-Section/4-Section) ................................................................................................................. 51

Solenoid Valves ................................................................................................................................................... 67

Proportional Control Solenoid ............................................................................................................................. 75

Selector Valve ..................................................................................................................................................... 77

Port Relief Valve ................................................................................................................................................. 79

Shut-Off Valve .................................................................................................................................................... 81

Pilot Valve: S/N 17520003~17520208 ................................................................................................................ 83

Pilot Valve: S/N 17520209~ ............................................................................................................................. 94-1

Pilot Valve (Swing) ............................................................................................................................................. 95

Cylinders .............................................................................................................................................................. 99

Dozer Blade Cylinder ........................................................................................................................................ 115

Ram Lock Cylinder ........................................................................................................................................... 117

Slew Motor ........................................................................................................................................................ 123

Axle Type: 279/172

Axle Type: 212 (Front)

Axle Type: 112 (Rear)

Travel Motor Type: A6VM

Drop Box Type: 357

Swivel Joint Type: 532

Content .. 6 7 8 9 ..