Creation: 1.15 – 2013

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CHAPTER 3

OVERHAUL/MAJOR REPAIRS

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I-COMPONENT OVERHAULS

This section deals with the overhaul and repair of components within the ACU-804 Air

conditioning unit.

This section details the procedures recommended for the overhaul of the components after the

removal from the unit as detailed in Chapter 2, Section 3, and Removal/ installation.

There are no specific overhaul periods recommended. The engine should run for many thousand

of hours without requiring major attention. But should the engine be removed for a major repair

repaired after a considerately period of service, it is advisable to overhaul the unit or fit a factory

recondition replacement.

1-ENGINE

If the engine needs to be overhauled. We recommended that a certified service station

recommended by the engine manufacturer perform the overhaul, as special tools a fixtures

are needed cost having a service station do the work is well invested.

Regular maintenance, tune-up, and adjustments information is located in Chapters 2, and 5.

Follow the removal and installation instructions in chapter 2 when removing the engine for

overhaul.

A-REMOVAL FOR OVERHAUL/SERVICING

(1) Guards

(a) Remove the blower belt guard.

(b) Remove the engine accessory belt guard

(2) Hoses

(a) Drain the engine coolant from the petcock located on the engine on the

blower side of the unit.

(b) Disconnect all coolant hoses from the engine (C7)

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(c) Disconnect the suction line from the hydraulic pump and drain the hydraulic

fluid into a suitable clean container. Disconnect the discharge line.

(d) Remove the hose clamps as required so that hoses may be pulled back and

tied out of the way of injury during engine removal process.

(e) Remove the rubber hose elbow from the engine air intake filter housing and

engine (C7). Tape the engine opening securely to prevent contamination.

(3) Electrical

(a) Disconnect and remove the batteries (BTI, BT2).

(b) Disconnect all electrical wires, battery cables, and engine harness from the

engine (C7).

(c) Remove the cable clamps as required so that the engine wires may be pulled

back and tied to prevent damage during the removal procedure.

(4) Mechanical

(a) Disconnect the flexible coupling between the power take-off and compressor

(b) Relax the tension on the blower drier and remove from the sheave at the

power take off.

(c) Remove the hydraulic pump

(d) Remove the coolant expansion tank.

(e) Remove the front roof panel

(f) Disconnect the inlet filter from the engine

(g) Disconnect the combustion air hoses leading from the engine to the Charge

Air Cooler

(h) Remove the exhaust silencer and support from the base

(i) Remove the screw and pin holding the front engine mount to the unit base

(j) Remove the screws and pins holding the rear engine mount to the unit base

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(k) Using a suitable forklift, lift the engine (C7) up to clear the structure and out

the front of the unit.

(l) If necessary, the power take-off assembly and engine starter relay may be

removed after engine has been removed.

B-INSTALLATION

(1) Mechanical

(a) If necessary, install the engine oil pressure switch (S31), the starter relay and

other accessories on the engine (refer to the Manufacturer’s literature, Chapter 5).

(b) If necessary install the power take-off on the engine (See the Manufacturer’s

literature, Chapter 5)

NOTE:

After installing the power take-off, check for ease of rotation of the output shaft with the

clutch disengaged. Ensure the grease fitting in the end of the power take-off shaft had been

removed.

(c) Install the engine onto unit I the same manner as removed.

(d) Align the engine (C7) with the compressor (C1) (see chapter 2, section 1) and

bolt in place.

(e) Recheck the alignment and dowel the rear engine mount to the engine

structure.

NOTE:

Alignment must be checked after tensioning the blower belt.

(f) Reinstall the exhaust piping and connect it to the engine

(g) Align the blower drive sheaves (See Compressor C1). Install the drive belt,

and then tension (See chapter 2, section 1)

(h) Recheck the alignment of the engine (C7) and the compressor (C1).

(i) Install the flexible coupling between the power take-off and the compressor

(2) Electrical

(a) Install the engine harness, battery cables, etc., on the engine (C7) as shown in

the wiring diagram.

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(b) Install the battery (BT1).

(3) Hoses

(a) Connect the fuel feed and return hoses to the engine.

(b) Connect all coolant hoses to the engine (C7).

(c) Connect the combustion air hoses leading from the engine to the Charge Air

Cooler

(d) Add coolant (See chapter 2, section 1) to the unit and check for leaks.

(e) Install the rubber hose elbow from the engine intake air filter to the engine air

intakes.

(4) Guard and Doors

(a) Install the blower belt guard and the bottom shield.

(5) General

(a) Check the engine coolant and oil level.

(b) Check for lubrication of the power take-off.

(c) Check for loose or missing parts or wires.

(d) Connect the battery cables to the battery (BT1).

(e) Start the engine and check for leaks or electrical problems.

(f) If the engine performs properly, shut down the engine and clamp or lace

hoses, wires, and cables to prevent damage.

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1 2

3

4

5

1…Coolant expansion tank

2…Roof panel

3…Exhaust silencer support

4…Exhaust system

5…Charge air cooler

ENGINE REMOVAL / INSTALLATION

FIGURE 35

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2-COMPRESSOR

If the compressor needs to be overhauled, we recommended that a certified Frick service

station do the work. Special tools and fixtures are needed to overhaul this compressor and the

cost of having a service station do the work well invested.

Regular maintenance, tune-up, and adjustments information is located in Chapters 2 and 5.

Follow the removal and installation instructions in Chapter 2, when removing the compressor

for overhaul. Ensure all troubleshooting steps have been followed.

A-COMPRESSOR REMOVAL/INSTALLATION FOR SERVICING

WARNING:

REMOVE ALL RESIDUAL PRESSURE FROM THE SYSTEM BEFORE REMOVING

THE COMPRESSOR.

(1) Removal

WARNING:

THE REFRIGERATION COMPRESSOR SHOULD NOT BE ALLOWED TO STAND

FOR AN EXTENDED PERIOD OF TIME EXPOSED TO AIR AND MOISTURE. TAKE

PRECAUTIONS TO PREVENT THE ENTRANCE OF AIR AND MOISTURE AS SOON

AS POSSIBLE. ALLOWING RUST TO FORM INSIDE A COMPRESSOR

JEOPARDIZES THE COMPRESSOR WARRANTY AND MAY RENDER IT

IRREPARABLE.

(a) Pump down the refrigeration system to minimize the loss of refrigerant and

close the receiver vales (See Chapter 2, section 1).

(b) Carefully open the caps on the purge ports (P10) and (P11).

(c) Disconnect the tubing from the compressor.

(d) Disconnect the liquid injection line.

(e) Unbolt the suction flange from the compressor.

(f) Unbolt the discharge flange from the compressor and discharge line.

(g) Remove the oil piping.

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(h) Remove the belt guard.

(i) Disassemble the compressor coupling.

(j) Remove the bolts and dowels from the compressor feet.

(k) Lift the compressor with a fork lift and a suitable lifting device.

Prevent air moisture form entering the refrigeration system. If the unit is to stand

for any length of time without a new compressor installed, seal all opening with

clean rags, plastic, tape, etc.

(2) Installation

(a) New compressors are shipped with gas holding charge to prevent the entrance

of air and moisture. Purge the holding charge carefully.

(b) Remove the covers from the suction and discharge ports.

(c) Left the compressor with forklifts and install through the oil separator side of

the unit.

(d) Align the compressor per instructions in * Adjustments*, Chapter 2, section

1.

(e) Dowel the compressor in place when the proper alignment has been attained.

(f) Install the compressor coupling.

(g) Install the suction and discharge piping flanges (use new gaskets).

(h) Connect the oil piping to the compressor.

(i) Connect the liquid injection line to the compressor.

(j) Cap all purge ports.

(k) Gas charges the system and compressor with refrigerant through ports (P6)

and (P7).

(l)Leak check the compressor and associated components disturbed by the above

procedure.

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(m) Evacuate the system and compressor to 300 microns of mercury absolute or

less.

(n) Gas charge the system to approximately 30 psi through test ports (P9) and

(P16).

(o) Re-torque the bolts including the coupling after several hours or operation.

(p) Operate per the operating instruction given in chapter 1, section 2. Adding

refrigerant and adjust the oil level. (See chapter 2, section 1) as required.

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COMPRESSOR REMOVAL /INSTALLATION

FIGURE 32

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3-RUNNING GEAR

For normal airport duties it is unlikely that the unit will be towed to such and extent that the

running gear will need major attention other that the replacement of the tires.

A-DISSASEMBLY (See Figure 1)

(1) Remove the rim and tire assembly.

(2) Remove the grease cap (figure 1, item 10) take out the cotter pin (figure 1, item 9),

and remove the nut (figure 1, item 8) and the washer (figure 1, item 7) on each hub.

(3) Withdraw the outer bearing race (figure 1, item 6) and pull the hub assembly (figure

1, item 1) off the spindle.

(4) Remove the inner bearing race (figure 1, item 3) and the grease seal (figure 1, item

2) from the spindle.

B-CLEANING

(1) Clean the metal parts using mineral based solvent. Do not allow solvent to come

into contact with the tires.

(2) Remove the old grease from the grease cap and hub bearings.

C-INSPECTION

(1) Inspect the hub bearings and cups for pitting of rollers and cup surfaces. Renew if in

doubtful condition.

(2) Check the integrity of welds on the axle, spindle, and the swivel assembly.

(3) Inspect the spring leaves for faltering and worn bushing.

(4) Check the spring bolts for damage or wear.

(5) Inspect the towbar and brake assembly for damage or wear.

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D-REPAIR

The repair of any defective part is accomplished by the replacement of the part

concerned.

E-ASSEMBLY

1) Lightly oil the leaf spring and fit it to the axle, tightening the bolts securely

2) Fit the new grease seal (figure 1, item 2) to the spindle followed by the inner bearing

cone (figure 1, item 3)

3) Pack the hub cavity approximately half full with grease (ML-G-10924C or

equivalent, including TLD-ACE part number UMG2-1). Smear the grease on the

bearing rollers (figure 1, item 3 and 5).

4) Slide the hub (figure 1, item 7) onto the spindle and fit the outer bearing cone (figure

1, item 5).

5) Fit the washer (figure 1, item 7) and the nut (figure 1, item 8) and tighten until; the

bearing binds.

6) Loosen the nut (figure 1, item 8) approximately one flat to expose the cross drilled

hole in the threads as needed to insert the cotter pin.

7) Check that the hub rotates freely with no perceptible wobble. Fit the new cotter pin

(figure 1,item 9)

8) Pack the grease cap (figure 1, item 10) with grease and tap into the recess in the hub

(figure 1, item 1)

9) Fit the rim and tire assembly and tighten the nuts securely.

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1…Hub 8…Nut, castellated

2…Seal, grease 9…Pin, cotter

3…Bearing, inner cone 10…Cap, grease

4…Bearing inner cup 11…Wheel stud

5…Bearing outer cone 12…Wheel nut

6…Bearing outer cup 13…Washer

7…Washer, keyed

HUB ASSEMBLY

FIGURE 1

2

3 4

1

6

5 9

10

7 8

13 12

11

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4-EXPANSION VALVE REMOVAL/INSTALLATION (See Figure 34)

A-Malfunction

The body of the expansion valve is soldered into the refrigeration line. A common

cause of poor operation is particles being stuck at the seat of the valve and/or ice from

moisture in the system. The filter drier may also be clogged.

When disassembling the power assembly and cage from the valve body, inspect for

particles, signs of moisture, or missing gaskets (figure 34, item 7). Replace cage only

if the cage is physically jammed or an obvious defect is visible. Replace the power

assembly only if a leak is found from the bulb capillary tube, diaphragm case, or if

the expansion vale refuses to open.

B-REMOVAL OF THE POWER AND CAGE ASSEMBLIES

(1) With the unit running, close the receiver outlet valve (V17) and allow compressor

to pump the R-134a into the receiver and shut down.

(2) Remove the equalizing line connection at the power assembly and plug.

(3) Remove the two bolts that hold the power assembly to the valve body and remove

the bulb from the socket.

(4) Remove the power assembly and cage assembly.

(5) Replace all gaskets and parts as required.

(6) Remove the bulb from the bulb well if the power assembly is to be replaced.

C-INSTALLATION OF THE POWER AND CAGE ASSEMBLIES

(1) Install the cage assembly into the power assembly. Ensure the cage assembly does

not hang up o the adjusting gear.

(2) Install the power and cage assembly onto the valve body and tighten the bolts

evenly.

NOTE:

Ensure all gaskets (Figure 34, item 7) are in place since leak checking the vale after installation would not verify that the gasket is in place.

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(3) Connect the equalizing line to the power assembly

(4) Cover the bulb with a non-hardening heat transfer paste and insert it in the bulb

well. If heat paste is not available, wrap the bulb in aluminum foil. Vacuum the

TXV area.

(5) Open the receiver outlet valve (V17). Check for leaks.

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1…Power head assembly 6…Adjustment screw

2…External equalizer port 7…Adjustment screw cap

3…Remote bulbs 8…Body

4…Gaskets 9…Cap screw

5…Cage assembly

THERMO EXPANSION VALVE REMOVAL/ INSTALLATION

FIGURE 34

1 2

3

4

5

6

7

8

9

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