ATTB

NORTHROP GRUMMAN

Unscheduled Maintenance

Date Test Miles Service Activity Downtime Hours
11-19-97 101 Air system will not build pressure. Blown head gasket in air compressor replaced. 24.0 2.0
01-19-98 718 Air system will not build are pressure. Blown head gasket in air compressor replaced. 16.0 2.0
02-16-98 959 Air system will not build air pressure. Blown hed gasket in air compressor replaced. 1.0 1.0
03-11-98 1809 The air compressor head gasket is blown. Company rep. replaced air compressor head gasket. 2.0 2.0
03-16-98 1978 Air line frozen. Company rep. thawed out air line. 4.0 4.0
04-14-98 3182 New air compressor unit arrived. Unit installed. Wiring on new unit is different. Wiring harness modified by company rep. 24.0 1.5
04-14-98 3182 New air compressor unit arrived. Unit installed. Wiring on new unit is different. Wiring harness modified by company rep. 24.0 1.5
11-19-97 101 A bolt fell out of the driver's information screen. Bolt replaced. 0.5 0.5
02-11-98 856 The mounting bracket for the fire suppression extinguisher (engine compartment) is loose. Four nut inserts are pulled out of the bracket. Replaced inserts with nuts and washers. 1.0 1.0
03-17-98 2089 The seat at the right rear wheel well is broken. Seat removed and weight placed on the floor. 0.5 0.5
03-18-98 2251 Rear seat broken. Seat repaired. 1.0 1.0
04-27-98 3182 The right front rear view mirror will not adjust. Ring adjustment redrilled and roll pin relocated. 3.0 3.0
04-27-98 3182 The right front rear view mirror will not adjust. Ring adjustment redrilled and roll pin relocated. 3.0 3.0
07-02-98 5084 The left corner bumper trim fell off. Bumper trim replaced. 2.0 2.0
11-19-97 101 The response time for parking brake application is slow. Hydraulic system bleed at the rear wheel parking brake actuators. 0.5 0.5
03-31-98 2922 The air compressor mounting plate is broken and the parking brake cable is broken. Company rep. fabricated and installed a new air compressor mounting plate. Parking brake cable ordered. 8.0 4.0
04-02-98 2996 Parking brake cable arrive. Parking brake cable installed on left rear wheel. While replacing brake cable, the return spring for the forward shoe andthe hold-down spring for the rear shoe were found to be broken. Right rear wheel removed for inspection. All but one spring was found to be broken or damaged. The lining is damaged from broken parts. Complete brake kits ordered for both rear wheels and brake cable for the right rear wheel. 3.0 3.0
04-03-98 2996 Brake parts arrived. Installed brake kits in both rear wheels and replaced the right rear brake cable. 3.0 3.0
05-01-98 3182 Suspect air in brake system. Bleed hydraulic brake system, bleed parking brake activating system. 1.5 1.5
07-02-98 5084 The brake line below the driver's area was crushed by the steering arm. Brake line replaced. 2.5 2.5
07-06-98 5084 The brake line at the junction of the rear suspension is leaking hydraulic fluid. Line replaced and parking and service brakes bled. 3.0 3.0
08-07-98 5514 The left rear brake cable, brake springs and retainers failed. Brake kit installed in left rear brake. 6.0 6.0
09-11-98 6266 Brake sysem needs to be bled due to light application. Bleed brake system. 3.0 3.0
09-15-98 6389 Brake system needs to be bled due to light application. Rear wheels removed and service and parking brakes bled. 6.0 6.0
10-13-98 7414 Left side parking cable failed. Parking brake cable replaced. 6.0 6.0
11-24-97 282 No heat in the driver's compartment. Trouble-shoot electrical circuits, no problems found. Circuit breakers for the heater and defroster reset. 3.0 3.0
11-26-97 343 24 volt "Pioneer" inverter on roof failed. Inverter replaced. 72.0 2.0
12-03-97 517 Test bus disabled on durability track. Engine runs, bus will not move. Action pending company reps. instructions. 1016.0 1.0
12-08-97 517 Test bus disabled on durability track. Engine runs, bus will not move. Bus towed to repair shop. 3.0 3.0
12-08-97 517 Engine runs, bus will not move. Wheel motor inverter removed as per reps. request. 2.0 2.0
01-05-98 517 Engine runs, bus will not move. All four batteries replaced. New batteries are longer, minor modifications made to battery tray. 1.5 1.5
01-20-98 764 Test bus will not start. Charged batteries for 30 minutes. 44.0 0.5
02-02-98 764 Driver's monitor failed. Monitor replaced. 24.0 8.0
02-06-98 764 Engine shutting down and steering loss. Company rep. trouble-shooting. 120.0 8.0
02-11-98 856 Air conditioning will not function. Trouble shooting A/C power inverter. 24.0 1.0
02-13-98 959 Bus shutting down. Company rep. requests monitoring readings on wheel motor "B" pressure. Removed wires C3 and C4 from J1 connector on the wheel motor inverter. Bus now operates on the durability track without shutting down. 72.0 3.0
02-18-98 959 Trouble-shooting intermittent problems with the wheel motor system. Company rep. requests the upper PC board for the wheel motor inverter be replaced. PC board replaced. Wheel motor "B" failure still occurring. 192.0 3.0
02-26-98 1094 Wheel motor in degraded mode. Company rep. replaced wheel motor inverter. 24.0 7.0
03-04-98 1232 Driver's monitor failed. Company rep. replaced driver's monitor. 10.0 2.0
03-18-98 2251 Driver's monitor failed. Company rep. replaced monitor. 3.0 3.0
03-19-98 2353 Doors will not function properly. Company rep. trouble-shoot with vehicle management computer. Loose jumper wire connected. 8.0 8.0
03-20-98 2387 Continuous generator malfunction on fueling trip. Test bus towed to test track. 72.0 2.0
05-08-98 3236 Company rep. requests D-Dec, Electronic Control Module (ECM) and fuel filters be replaced. D-Dec, ECM and fuel filters replaced. Engine cranks but will not start. 2.0 2.0
05-19-98 3345 Engine shutting down. Trouble shooting with computer found problem on cooling system pressure circuit in genset. Circulating pump is running noisy. New circulating pump ordered. 2.0 2.0
05-20-98 3345 Circulating pump arrived. Replaced circulating pump and motor. 2.0 2.0
05-22-98 3345 Engine shutting down. As per reps. request; installed new alternator, voltage regulator, battery equalizer, and related wiring. Installed new engine idler pulleys and belt. Disconnect existing 12 volt battery and removed. Disconnect existing 12-24 volt system wiring from inverter. 96.0 8.0
05-26-98 3345 Completed work from 5/22/98 repairs. Completed wiring connections and road test. Engine shut down once with cooling system pressure failure intermittent problem. 48.0 2.0
06-04-98 3580 Engine shutting down. As per company reps report; replaced primary control computer with a more rugged version. Engine calibration factors were off int he software which caused the engine RPM's to be high and shut down the engine occasionally. Replaced the VMC with the original one. Disconnected and then reconnected all connectors associated with the cooling pressure system, which seemed to clear up the associated gneerator malfunction. Vehicle went on to the track. The throttle problem reappeared and the vehicle was parked. 24.0 8.0
06-05-98 3619 Engine shutting down. As per company reps report; initially the throttle issue was not present on the first power-up. After running on the test track for approximately 45-60 minutes, the cooling fan shut off causing the engine temperature to rise. The engine went into its protection mode and limited the available power to the wheels and gives the appearance of a throttle problem. It appears this is the same failure that has occurred over the past few weeks. Requested that another fan inverter be sent. 24.0 8.0
06-06-98 3619 Engine shutting down. As per company reps. report; recalibrated min/max throttle setting in reggedized VCM and reinstalled in bus. Began removal process of the engine cooling fan inverter. 24.0 8.0
06-07-98 3619 Engine shutting down. As per company reps. report; removed fan inverter from bus and installed new inverter. Rerouted several cables around the generator area which carry the pressure/cooling sensor data. 24.0 8.0
06-08-98 3619 Engine shutting down. Removed first stage GFI regulator, and replaced with a different ITT module. New regulator mounted directly under the air cleaner. Installed new coolant lines to the regulator. Added and extra 22' long fuel between the first and second stage regulators. Installed temporary jumper wires to the fuel shut off valve (wiring harness is too short/incorrect weatherpack connector). Proper connector and wiring harness ordered. 24.0 6.0
06-09-08 3619 Proper connector and wiring harness arrived. Connector and wiring harness installed. Drained and replaced jet oil in generator cooler. 24.0 3.0
06-11-98 3619 Engine shutting down. Company rep. repaired burned section of the cooling fan motor hall sensor cable. 2.0 2.0
06-16-98 3744 Experienced Ground Fault Interrupt (GFI) on the high voltage side. Company rep. traced the GFI to 4 of the wheel motor cables (insulation chaffed off). Reinsulated the cables and secured better. Now experiencing engine problems that seemed to be related to the throttle signal. 23.0 8.0
06-18-98 4200 Erratic speed signal. Company rep. replaced the signal cable from the VCM to the wheel motor inverter. 2.0 2.0
07-06-98 5084 Company rep. requests the driver's monitor be replaced. Driver's monitor replaced. 1.0 1.0
07-06-98 5084 The radiator fan motor failed. Genset removed to allow access to fan motor. Fan motor replaced and genset reinstalled. 1.5 1.5
07-17-98 5318 Power inverter failed. Company rep. replaced the circuit board in the inverter. Inverter still not functioning. 24.0 8.0
07-17-98 5318 Power inverter failed. Complete power inverter replaced. 264.0 8.0
08-03-98 5435 The bottom rear inverter failed. Inverter removed. 24.0 4.0
08-04-98 5435 The bottom rear inverter failed. New inverter installed. 72.0 8.0
08-15-98 6112 The power steering pump inverter has failed. Power steering pump inverter replaced. 4.0 4.0
08-19-98 6208 Gen./Aux. Inverter has failed. Company rep. replaced Gen./Aux. Inverter. 4.0 4.0
10-06-98 7131 Gen./Aux. Inverter has failed. Company rep. replaced the Gen./Aux. Inverter replaced. Engine runs and shuts down immediately. Inverter removed for trouble shooting. 12.0 12.0
10-07-98 7131 Engine runs and shuts down immediately. Repairs made to inverter and reinstalled. 8.0 8.0
10-08-98 7131 D-Dec system has electrical malfunctions. Company rep. trouble shooting found damaged wires in the wiring harness, wires repaired. New harness ordered. 8.0 8.0
10-16-98 7620 HVAC Inverter A failed. Inverter replaced. 2.0 2.0
10-16-98 7620 Stand-by power regulator failed. Company rep. replaced OCM 2.0 2.0
03-23-98 2387 Continuous generator malfunction. Company rep. installed a new Output Control Modul (OCM). Adjusted ramp motor proximity sensor to prevent a falsse ramp signal. Found W26PA to W26AJA transition connector in VMC loose (slot 6A). Re-taped all intermediate connectors in the Vehicle Management Computer (VMC). Generator sensor harness replaced to correct generator shut-down due to loss of oil pressure signal. 8.0 8.0
03-24-98 2520 The lower height sensor bracket is broken and engine is over heating. Company rep. installed new height sensor bracket. Gnerator coolant sensor disconnected and bus towed off the durability track. 8.0 8.0
11-26-97 343 The radiator fan shroud is broken. Engine-generator set (Genset) removed to gain access to shroud. Fan shroud welded/repaired. 4.0 4.0
02-03-98 764 Trouble shooting "no run" condition. Company rep. removed genset to inspect throttle body. 24.0 6.0
02-04-98 764 Trouble shooting "no run" condition. Company rep. replaced throttle body and fuel regulator. 24.0 6.0
02-05-98 764 Engine shutting down. Generator malfunction light is on. Company rep. trouble-shooting reinstalled original D-Dec. 24.0 1.0
03-16-98 1978 D-Dec failed. Company rep. replaced D-Dec. 24.0 1.0
04-06-98 3182 Test bus disabled on test track. No power steering. Battery switches cycle and power steering circuit breaker checked. Check wiring. No problem found, company rep. informed. Found genset cradle broken near the left side lifting point at the rear and front of the cradle. 8.0 3.0
04-07-98 3182 Broken genset cradle and found air compressor framework broken. Genset and air compressor removed for inspection by rep. 168.0 3.0
04-14-98 3182 Genset cradle arrived. Components removed from broken cradle and installed in new cradle. 48.0 5.5
04-16-98 3182 New genset cradle installation. Throttle body and VMC replaced as per reps. request. Drilled holes in new cradle for hold-down bolts. 24.0 2.0
04-17-98 3182 New genset cradle installation. New fan blades installed. Genset reinstalled in bus. 24.0 1.0
04-17-98 3182 The mounting bracket for the upper inverter above the engine compartment is broken. Mounting bracket replaced. 0.5 0.5
04-17-98 3182 Both wheel motor control arms are cracked. The right rear arm is cracked approximately 9" from the forward mount (all but 1" is cracked). The left rear arm is cracked 4" long around the channel. Control arm removed for reps. inspection. 5.0 5.0
04-20-98 3182 Cracked wheel motor control arms. Both wheel motors removed for access to control arm bushings. 8.0 8.0
05-28-99 3478 Three isolator mounts and one support brace are broken on the wheel motor oil cooler (roof top right rear). Broken isolators removed and replaced with rubber spacers and bolts. Replaced broken support brace with 1 1/2" strap steel. 1.0 1.0
05-28-98 3478 Two support braces are broken on the electronic inverter cooler (roof top, left rear). Supports replaced with 1 1/2" strap steel. 1.0 1.0
05-28-98 3479 Engine shutting down. Replaced pressure sensor and wiring harness for the generator oil system. 1.0 1.0
06-03-98 3479 Engine shutting down. As per company reps. report; bus parked due to throttle related issue. Could not reproduce the failure on the test track. The vehicle was having generator malfunctions which were being caused by the previous pressure/cooling problem. The vehicle was taken for fuel and towed back due to the previous problem. 24.0 8.0
06-10-98 3619 Engine shutting down. Loose wire on the alternator excitation circuit. Company rep. tightened loose connection. 1.5 1.5
06-11-98 3619 Engine shutting down. Company rep. added 2 gallons of coolant, system low due to fuel pressure regulator change. 0.5 0.5
06-12-98 3619 Engine shutting down. Company rep. removed resister jumper on the generator IR sensor cable. 21.5 0.5
06-17-98 3744 Test bus experienced multiple engine shut-downs all related to the engine. Company rep. traced and disconnected and reconnected all connections on the generator, generator inverter, wheel motor inverter, and D-Dec. Reprogrammed max RPM on D-Dec to 2750. Engine problems seem to be gone. 24.0 8.0
07-06-98 5084 The air compressor skid is cracked. Skid welded/repaired. 2.0 2.0
10-09-98 7131 Test bus losing power while running. Company rep. trouble shooting electrical system. 8.0 8.0
10-09-98 7131 New D-Dec to ECU wiring harness arrived. Company rep. installed new wiring harness, oil pressure and temperature sensors. 4.0 4.0
10-16-98 7620 Engine losing power. Company rep. replaced throttle body. 3.0 3.0
04-27-98 3182 Found two safety CNG, PRD vent lines improperly capped. Replaced steel caps with plastic caps. 1.0 1.0
02-16-98 959 Test bus experiencing intermittent problems with the wheel motor system. Problem found with the PH2 and PH3 systems of the wheel motor. Company rep. informed. 24.0 2.0
02-17-98 959 Trouble-shooting intermittent problems with the wheel motor system. Checked connections on the invertor circuit board for the wheel motor, no problems found. 24.0 2.0
02-17-98 959 Test drive to trouble-shoot for intermittent problems with the wheel motor system. Running bus on the durability track; intermittent problem still exists in wheel motor "B". Also experienced an engine shutdown with a fault reading "sensor voltage low." Manufacturer informed. 2.0 2.0
11-20-97 166 The right rear most air bag is ruptured. Air bag replaced. 2.0 0.5
11-20-97 166 The area around the right side, rear most anchoring mount on the suspension arm is cracked. Company reps. repaired cracked area. 1.0 1.0
11-24-97 282 Test driver's report the bus is leaning. Ride height and air system checked out, no problems found. 1.0 1.0
11-26-97 343 Inspect right rear most suspension arm anchoring mount repaired 11/20/97. Repair ok. 1.0 1.0
12-01-97 427 The left rear most air bag ruptured. Air bag replaced. 1.0 0.5
01-16-98 683 Leveling valve arm fell off the left rear leveling valve. Company rep. replaced leveling valve arm. 16.0 0.5
02-26-98 1082 The front of the bus will not raise to the proper ride height. Company rep. switched to the left and right linear potentiometers. Problem still exists. 1.0 1.0
02-26-98 1094 Rear ride heigh sensor failed. Sensor replaced by company rep. 2.0 2.0
03-19-98 2353 The right front height sensor mount is broken. Company rep. replaced height sensor mount. 3.0 3.0
03-25-98 2593 The left rear height sensor has failed. Company rep. installed new height sensor. 16.0 2.0
03-26-98 2708 The right rear and the left front height sensors have failed. Company rep. installed new right rear and the left front height sensors. Also adjusted the rear door emergency switch and replaced a missing nut on the front door upper pivot. 4.0 4.0
03-30-98 2906 Bus cannot maintain proper front ride height. Company rep. installed new left front ride height sensor and repaired a broken wire. 2.0 2.0
04-03-98 2996 The right rear brake cable chaffed the right rear, forward air bag. Right rear, forward air bag replaced. 1.0 1.0
04-27-98 3182 The floor is cracked at the rear anchor point for the right rear wheel motor suspension. Company rep. will repair. 72.0 16.0
06-12-98 3619 The left rear height sensor failed and the windshield is coming out of the gasket at the top. Company rep. replaced the left rear height sensor and applied tape to the windshield. 1.0 1.0
06-15-98 3946 During fueling run, the left rear and right front height sensors failed. Company rep. replaced left rear and right front height sensors. 2.0 2.0
06-16-98 3744 The right front height sensor failed. Company rep. replaced the right front height sensor. 1.0 1.0
07-06-98 5084 The rear suspension mount is cracked. Removed rear suspension for repairs to suspension mount. 2.0 2.0
07-06-98 5084 Rear suspension pivot bushings are worn. Rear suspension pivot bushings replaced. 3.0 3.0
10-11-98 7170 Rear wheels; the left forward air bag failed. Company rep. replaced air bag. 2.0 2.0
03-05-98 1308 The steering arm is broken. Mounting bolts are loose and missing. Company rep. replaced bolts and reinstalled steering system. 72.0 3.0
11-21-97 259 Wheel motor warning message. Drained oil from both wheel motors and flushed with clean oil. Retrieved oil samples. Replaced SHC 320 oil and torqued wheels to 300 ft/lb. 24.0 6.0
03-08-98 1341 Electrical cable to wheel motor is broken. Cable rep. repaired with cable lugs. 2.0 2.0
05-01-98 3182 Engine runs, bus will not move. Right rear suspension and cover from wheel motor removed for inspection of wheel motor. 2.5 2.5
05-04-98 3205 Test bus disabled between shop and test track. 24 volt system will not recover. Traction system monitored with computer. Found an intermittent problem in wheel motor "B", cooling system pressure warning. Batteries charged, bus returned to test track. Intermittent fan loss and engine shutdowns. 6.0 6.0
06-18-98 4200 GFI fault on the wheel motor cables. Reinsulated the cable and secured. 6.0 6.0
06-18-98 4284 Both front tires are worn. Front tires replaced. Brake pads inspected. 4.0 4.0
07-28-98 5365 GFI in the wheel motor. Company rep. repaired chaffed insulation on wheel motor cables. 6.0 6.0
08-10-98 5515 Wheel motor malfunction. Company rep. removed wheel motor inverter and reinsulated wheel motor cables. 8.0 8.0
08-13-98 5847 The right side wheel motor is making noise. Company rep. drained oil and refilled. 2.0 2.0
10-16-98 7620 Both front tires are worn. Both front tires replaced. 2.0 2.0
10-16-98 7620 Wheel motor malfunctioned. Company rep. repaired chaffed wheel motor electrical cables. 4.0 4.0
03-03-98 1225 Insulation on electrical cables to the wheel motor are chaffed. Company rep. repaired with cable lugs. 24.0 2.0