Tesco ML50-20 Maintenance Manual Download Page 22 | Manualshive

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TROUBLESHOOTING

2-3

Page 3

ML50-20 MAINTENANCE LIFT

TESCO EQUIPMENT LLC

When a component is repaired or replaced, always check the hydraulic circuit for the correct indicated
pressure, correct actuator speeds, and correct hydraulic fluid level.

A.

Troubleshooting Chart - General

TROUBLESHOOTING

TROUBLE

PROBABLE CAUSE

Ground level controls will not operate with the
vehicle’s engine running.

Vehicle not in lift mode (Parking brake off)

Emergency stop activated

Circuit breaker tripped or blown fuse

Defective solenoid coil or relay

Damaged or defective control switch

Damaged wiring or bad ground

Damaged Power Take Off (P.T.O.) or pump drive
components

Stabilizers will not hold retracted or extended
position.

Faulty check valve

Faulty cylinder

Stabilizers will not retract.

Vehicle not in lift mode (Parking brake off)

Hi-Lift not fully lowered or stowed

Circuit breaker tripped or blown fuse

Defective relay

Defective Hi-Lift or stabilizer interlock switch

Damaged or defective control switch

Defective valve cartridge

Damaged wiring or bad ground

Damaged Power Take Off (P.T.O.) or pump drive
components

May 08

Property of American Airlines

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Summary of Contents for ML50-20

Page 1: ...MAINTENANCE LIFT Maintenance Manufactured by Tl8t D TE co EQUIPf fENT LLC Coral Springs Florida P r o p e r t y o f A m e r i c a n A i r l i n e s ...

Page 2: ...L INFORMATION 1 INTRODUCTION 2 HYDRAULIC SYSTEM 2 ELECTRICAL SYSTEM 2 TROUBLESHOOTING GUIDE 2 Troubleshooting Chart General 3 INTRODUCTION 1 STRUCTURAL REPAIRS 1 Scissor arms 1 Scissor frame platform 1 Handrails 1 Surface rust or scratches 1 HYDRAULIC SCHEMATIC 1 4 Stabilizers and Return Filter Figure 1 1 ELECTRICAL SCHEMATIC 1 How to Read This Schematic Figure 2 1 ELECTRICAL SCHEMATIC SHEET 1 OF ...

Page 3: ...tents Page 2 TESCO EQUIPMENT LLC ML50 20 MAINTENANCE LIFT ELECTRICAL SCHEMATIC SHEET 6 OF 7 Figure 8 1 ELECTRICAL SCHEMATIC SHEET 7 OF 7 Figure 9 1 Jan 14 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

Page 4: ...EM Page 5 Section 3 Troubleshooting Section 4 Repairs Section 5 System Schematics 2 5 Figure 1 HYDRAULIC SCHEMATIC ML2 WITH RETURN FILTER Page 2 2 5 Figure 2 HOW TO READ THIS SCHEMATIC Page 5 2 5 Figure 3 ELECTRICAL SCHEMATIC SHEET 1 OF 7 Page 6 2 5 Figure 4 ELECTRICAL SCHEMATIC SHEET 2 OF 7 Page 7 2 5 Figure 5 ELECTRICAL SCHEMATIC SHEET 3 OF 7 Page 8 2 5 Figure 6 ELECTRICAL SCHEMATIC SHEET 4 OF 7...

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Page 6: ... obvious damage missing parts and fluid leaks X Check spotlights indicator lights and beacon lights X Check hydraulic oil level X Check condition of all handrails and mounting brackets X Check condition of operator s boarding steps X Check fire extinguisher levels Make sure they are secured in their mounting brackets optional X Inspect pivot pins on platform cylinders for wear X Check scissors piv...

Page 7: ...ity fluid may be substituted Check platform understructure for cracked welds or corrosion X Check condition of placards and safety warning decals X Replace return filter 6 mos Check that all wiring terminals are secure Annually Replace corrosion inhibitor in main electrical control box Annually Drain hydraulic reservoir and clean Annually Check hoist rollers for wear X No more than 1 4 wear OIL OP...

Page 8: ...R 1 Check hydraulic oil level as described above 2 Determine the amount of oil to be added 1 8 gallons of oil will raise the level in the reservoir about 1 inch 3 Raise the van body if necessary to access the reservoir filler cap Support platform with the main tenance stand 4 Clean the area around the filler breather cap 5 Remove cap and check strainer screen for any foreign material 6 Clean thoro...

Page 9: ...l to reduce cylinder noise as needed which may be caused by dry seals NOTE The scissors lift must be raised to access the grease points NOTE Check at intervals listed and lubricate as required In unusual weather conditions check at more frequent intervals WARNING THE SCISSOR LIFT MUST BE SECURED WITH THE MAINTENANCE PROP BEFORE ACCESSING THE GREASE POINTS GREASE POINTS ITEM COMPONENT TOTAL FITTING...

Page 10: ...CE LIFT TESCO EQUIPMENT LLC Figure 2 GREASE POINTS DIAGRAM 1 2 2 1 2 GREASE ALL TRACKS 3 4 Ref Figure 4 Ref Figure 4 Ref Figure 4 Ref Figure 3 Ref Figure 4 Ref Figure 4 Ref Figure 4 May 08 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

Page 11: ... LLC ML50 20 MAINTENANCE LIFT Figure 3 GREASE POINTS LIFT CYLINDER UPPER ROLLER GREASE POINT NOTE Do not grease bleed valve shown below BLEED VALVE GREASE POINT BUTT END OF CYLINDER May 08 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

Page 12: ...REASE POINTS ROLERS AND PINS SCISSOR UPPER LOWER ROLLERS BOTH SIDES SCISSOR UPPER LOWER PIVOT PINS BOTH SIDES GREASE POINT GREASE POINT REAR FWD SCISSOR CENTER PINS BOTH SIDES UPPER AND LOWER SCISSOR ARM END PINS 4 PLCS May 08 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

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Page 14: ...VEMENT OF THE UNIT IN EITHER DIRECTION WARNING WHEN MAKING PRESSURE CHECKS OR ADJUSTMENTS USE GAUGES WITH KNOWN ACCURACY IMPROPER HYDRAULIC ADJUSTMENTS CAN CAUSE INJURY TO PERSONNEL OR DAMAGE TO EQUIPMENT WARNING DO NOT REMOVE GAUGE PORT PLUGS OR GAUGES OR LOOSEN HYDRAULIC CONNECTIONS WITH THE UNIT RUNNING HYDRAULIC PRESSURE IN THE SYSTEMS COULD CAUSE HYDRAULIC OIL TO SPRAY ON PERSONNEL CAUTION US...

Page 15: ...latform to minimize the weight on the scissor lift NOTE Remove UP limit switch on scissors in order to achieve full extension on lift cylinder 2 Raise the scissor to the maximum height 3 Secure the scissor lift with maintenance props 4 Leave the scissor lift at maximum height for one hour or more leave overnight if possible to allow any air entrained in the hydraulic oil to rise to the tops of the...

Page 16: ...LIFT TESCO EQUIPMENT LLC 12 With the scissor in its fully lowered position check the hydraulic oil level Refill reservoir if needed Figure 1 LIFT CYLINDER BLEED VALVE BLEED VALVES BLEED VALVE DETAIL VIEW May 08 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

Page 17: ...lve clockwise to slow stabilizer speed counter clockwise to increase stabilizer speed Tighten locknut when adjustment is complete E Stabilizer Pressure Reducing Valves N A Fully retract lift and stabilizers Turn valve fully clockwise and extend retract stabilizers till all stabilizers operate smoothly and consistently with the left rear stabilizer last to extend and last to retract See Adjustment ...

Page 18: ...HYDRAULIC SYSTEM ADJUSTMENTS 2 2 Page 5 ML50 20 MAINTENANCE LIFT TESCO EQUIPMENT LLC Figure 2 HYDRAULIC SYSTEM A B C D STABILIZER F G E Jan 14 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

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Page 20: ...vided as a guide to assist technical service personnel in troubleshooting operational malfunctions in the ML50 20 Lift hydraulic and electrical systems 1 Before starting troubleshooting procedures verify that the correct operating procedures were used An incorrect operating procedure can cause apparent malfunctions 2 The most important practice to observe when working on the hydraulic system is cl...

Page 21: ...t or emergency operation the hand pump or optional electric auxiliary hydraulic pump may be used to provide hydraulic flow Press both UP switches simultaneously if not equipped with an ENABLE switch In this case one of the UP switches function as the ENABLE switch 3 ELECTRICAL SYSTEM The Model ML50 20 has a 12 volt DC electrical system that controls all functions of the Hi lift The components of t...

Page 22: ...ed or blown fuse Defective solenoid coil or relay Damaged or defective control switch Damaged wiring or bad ground Damaged Power Take Off P T O or pump drive components Stabilizers will not hold retracted or extended position Faulty check valve Faulty cylinder Stabilizers will not retract Vehicle not in lift mode Parking brake off Hi Lift not fully lowered or stowed Circuit breaker tripped or blow...

Page 23: ...nual overrides not open Upper controls will not operate with the vehicle s engine running Vehicle not in lift mode Parking brake off Stabilizers not fully deployed Emergency stop activated Circuit breaker tripped or blown fuse Damaged or defective control switch Defective solenoid coil or relay Damaged wiring or bad ground Damaged Power Take Off P T O or pump drive components Vehicle s engine will...

Page 24: ...rtridge valve Hi lift unit racked or twisted in one direction during raising or after reaching required height Exceeding maximum load capacity Off center load on work platform Air trapped in lift cylinder Faulty or damaged holding valve on the lift cylinder Leak in one of the lift cylinder Low hydraulic fluid level in reservoir Faulty hi lift scissors center pivot pin attach pin or roller axle Hi ...

Page 25: ...lic oil viscosity too light for climate Hydraulic oil flowing over relief valve Relief valve pressure is set too low or too high Worn pump or internal damage to pump Hydraulic oil pump is noisy Low hydraulic oil level Hydraulic oil viscosity too heavy Restricted hose or collapsed suction hose Air leak in suction hose between suction outlet and pump s inlet port Hydraulic oil temperature too high P...

Page 26: ...D 1595 Welded joint configuration and preparations must be in accordance with existing AWS DD1 1 welding code for structural welding 2 STRUCTURAL REPAIRS A Scissor arms Welded repairs on scissor arm s structural tubing are not permitted Consult with Tesco for approved methods or guidelines for conducting repairs B Scissor frame platform Repair cracks or damage by welding or splicing as required ex...

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Page 28: ...ead This Schematic Figure 2 B ELECTRICAL SCHEMATIC SHEET 1 OF 7 Figure 3 C ELECTRICAL SCHEMATIC SHEET 2 OF 7 Figure 4 D ELECTRICAL SCHEMATIC SHEET 3 OF 7 Figure 5 E ELECTRICAL SCHEMATIC SHEET 4 OF 7 Figure 6 F ELECTRICAL SCHEMATIC SHEET 5 OF 7 Figure 7 G ELECTRICAL SCHEMATIC SHEET 6 OF 7 Figure 8 H ELECTRICAL SCHEMATIC SHEET 7 OF 7 Figure 9 Jan 14 P r o p e r t y o f A m e r i c a n A i r l i n e ...

Page 29: ...FRONT ALR AUX P 6 12 B1 12 A1 10 12 VDC EMERGENCY PUMP 1 8 NPT 8 16 SOL4 P T SOL3 ENGINE DRIVEN PUMP M SOL2 VALVE CHECK 1800 PSI NOM SYSTEM RELIEF P 100 400 PRFBLEN REDUCER PRESSURE T NEEDLE VALVE FLOW CONTROL AUX P G1 P1 3 1 2 4 SOL1 PBU VALVE OPTIONAL 6 6 STRAINERS ISOLATION VALVE TANK M 12VDC PUMP RESERVOIR 50 GAL HAND P2 PUMP S SUCTION D G2 04 LOWERING VALVES GRAVITY DOWN SOL6 B2 SOL6A POWER U...

Page 30: ...OIL D05 12VDC Lift Stabilizer 1 HYMS20041 VALVE D05 3 Pos 4 Way Stabilizer 1 HYMS20040 VALVE D05 2 Pos 4 Way Lift 1 HYMS20048 CARTRIDGE Lift Flow Control Valve 1 HYMS20045 GAUGE 0 2000 PSI 1 HYMS20046 CARTRIDGE System Relief Valve 1 HYMS20052 VALVE Check Inlet 1 HYFI10017 FILTER ELEMENT Return 3 2 HYVA10210 VALVE LOWERING 2 WAY N C 4 4 HYCY10046 CYLINDER Double Acting Stabilizer 5 2 HYCY10001 CYLI...

Page 31: ...THIS PAGE INTENTIONALLY LEFT BLANK TESCO EQUIPMENT LLC ML50 20 MAINTENANCE LIFT MAINTENANCE 2 5 Page 4 Mar 08 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

Page 32: ...17 7 1 66 6 5 6 1 7 6 2 5 6 6 7 2 9 211 7 216 21 6 7 5 211 7 21 32 17 12 75 211 7 21 7 50 1 1 0 1 2 5 180 5 1 5 0 32 17 2 5 7 6 2 237 216 5 0 5 1 7 21 21 1 8 1 0 1 81 7 21 2 66 0 6625 81 2 1 66 6 2 7 21 1 8 5 5 8 9 9 6 3 167580 17 3 1 67 67 56 9 0 8 09 8 5 5281 21752 67 7 21 67 5 21752 6 833 5 21752 67 7 21 7 2 25 25 3 7 250 6 6 66256 7 8 5281 9 21752 67 7 21 1 25 2876 8 5 833 5 21752 67 7 21 029 ...

Page 33: ...INE RESTART J10 UCS9 J11 UC10 UC2 J2 UCS 1 J1 IGNITION SWITCH IGNITION SWITCH PC 2 PC 1 GC 9 NEUTRAL PARK LOCK INDICATOR HOUR HOUR METER METER IP 7B 7B 7B 7B GROUNDED IN NEUTRAL TCM EN CC4 NEUTRAL PARK INDICATION TRANSMISION ENGINE STOPPED PARK BRAKE SET R14 STABS STOWED IGNITION 101 110 200 120 207 MB MB R12 MB MB MB R11 CR10 HIGH THROTTLE CR1 B CB1 10A CR1 IGNITION ON CR3 R13 R13 6 8 254 1 4 30 ...

Page 34: ...12V 12V PLATFOR WORK LIGHT BEACON LIGHT ICC LIGHTS REAR FLOOD LIGHT LT3 LT4 HEADLIGHT SWITCH SW3 PLATFORM WORK LIGHTS FLASHER BEACON SW6 SW7 LIGHTING 13 14 15 16 15A GC7 15 35 40 15A L X P MB J13 CB2 40A 211 MB 87 30 IGN ON CR3 R15 BODY DOWN BODY DOWN LIGHTS 116 R15 211 8 6 1 4 MAIN BOX MAIN BOX H 204 CHASSIS CHASSIS LT 5 LT 5A 35 40 UCS11 UCS12 UCS6 UCS13 GRN RED ORANGE BLUE 14 16 12 0A 4 X 35W 2...

Page 35: ...VERRIDE OPT STABL STOWED IP SW11 30 CR4 87A 30 CR5 87A 87A 30 30 R13 87 8 6 CR4 B ENGINE STOP OPT CR6 BRAKE SET R14 85 86 CR7 R15 R16 R16 4 1 NEUTRAL CR8 NEUTRAL STABL STOWED STABL EXT D BODY DOWN STAB STOWED BODY DOWN CB3 20A LIFT CONTROL LIFT MODE 86 85 R14 STABS STOWED 86 85 CR8 86 STABL STOWED 85 CR5 118 120 118 205 215 213 207 113 MB ENG STOP OPT MB MB MB MB MB MB LIFT MODE 30 87 CR6 203 MB M...

Page 36: ... 12V PC3 PC4 GC 1 GC 2 AG 1 AG 2 AG 4 AG 3 HIGH THROTTLE 105 PC3 GC 1 PC3 GC 1 PC6 GC 4 GC 3 PC5 UC GC UC GC UP INHIBIT 261 LIFT DOWN SOL6 LIFT DOWN SOL6A LIFT DOWN SC SC 12V UC 6 UC 5 UC4 UC3 UCS3 OPT LIFT W O STABL S OPEN HEIGHT ALL MOTION ALARM OPT PBU OPT SOL1 C LS15 MV D 272 256 D BP ALARM OPT ALL MOTION 9 S1 S2 308 F R 311 S 312 T 313 STABL S EXTENDED CR7 BODY DOWN 6 8 R16 213 209 MB MB IGN ...

Page 37: ...ssor CH Compressor Solenoid CH Compressor Fan CH STABL RETRACT INHIBIT 308 COMPRESSOR SOL 9 CLOSED WHEN HOT 140 F HYD OIL TEMP TS1 MV 252 OIL OVERHEAT R LT10 IP HYD OIL OVERHEAT AIR COMPRESSOR C 255 251 F 268 T 262 S 1 R12 4 ENGINE RUNNING 114 IGN LIFT MODE LIFT 44 44 45 46 MAIN BOX MAIN BOX LT8 J4 RED ORANGE BLACK LIFT DOWN LIFT UP 258 R MB CR2 COMPRESSOR INHIBIT 30 CR2 87A 311 10 86 85 OIL OVERH...

Page 38: ...L PARK SIGNAL J 122 PIN 5 WHT RED 118 GROUNDED WHEN IN PARK 123 125 150 CHASSIS WIRE NO INPUT TO VEHICLE OR OUTPUT FROM VEHICLE 107 OUTPUT 12VDC WHEN PARKING LIGHTS ON ISUZU NPR 2008 2013 WITH AUTO TRANSMISSION NON ALLISON N A CC1 C PTO LEFT REMOTE CONNECTOR AT IGNITION SWITCH WHITE RED PIN C ON 8 PIN CONNECTOR Pink AT IGNITION SWITCH BLACK WHITE DRIVER DASH GREEN RED N A N A OUTPUT TO GROUND WHEN...

Page 39: ...NE 253 252 GC 1 ENABLE LOWER SW13 GC GC 2 SOL2 PTO EN PTO 12V 200 201 121 122 123 12V 12V IGN 12V 87 HIGH THROTTLE 254 CR10 227 30 E 4 LIFT 28 106 P S10 12V S11 LIFT MODE LIFT MAIN BOX OIL OVERHEAT 87a 30 CR21 300 30 CR4 87A 30 CR5 87A B ENGINE STOP OPT NEUTRAL CR8 STAB STOWED BODY DOWN 118 205 215 113 36 123 GROUND POWER 14 CR20 13 87A 30 CR8 BODY DOWN 215 MAIN BOX MAIN BOX ECM 253 P EN CHASSIS C...

Page 40: ...ents Page 1 Page ML50 20 MAINTENANCE LIFT TESCO EQUIPMENT LLC TABLE OF CONTENTS CHAPTER 3 OVERHAUL Section 1 Overhaul Procedure GENERAL INFORMATION 1 Apr 06 P r o p e r t y o f A m e r i c a n A i r l i n e s ...

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Page 42: ...section that covers the component should be read in full and understood completely before attempting an overhaul Units operating in extreme conditions such as high or low temperatures long periods of sustained operation continued operation in sand or dust or continued exposure to sea air or moisture need regular inspection Overhaul periods can vary For adjustment or repair of components refer to C...

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