Hyster Fault Codes Explained

Are the error codes on your Hyster W40Z or Yale MPB40-E pallet jack confusing you? Keep reading to learn what problems these codes indicate and how you can solve them. We’re not affiliated with the Hyster Company but we know a lot about Hyster forklifts and we like sharing our knowledge.

Q: How do I read Hyster W40Z or Yale MPB40-E pallet jack codes?

A: Hyster and Yale forklifts use the same control system, so error codes on Hyster forklifts are the same as those on Yale forklifts. These error codes can actually appear in many ways. While they can be communicated with flashes of a red LED bulb on the jack’s controller, this blog will cover the error codes presented on the jack’s dash display. Sometimes, an error code can mean one of many potential issues. In these cases, it may be necessary to use a special handset or PC to determine which of the problems is the cause of the error code.

Having trouble with error codes from another brand? Check out these other helpful links:

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Below are interpretations for the following error codes: no LEDs, no alarm, AL66, AL99, AL01, AL02, AL4, AL5, AL6, AL7, AL8, AL10, and AL94.

• Dash display: no LEDs or LCDs on
  Condition: inoperative
  Cause: B+ and/or B- missing at controller, defective battery charger, or defective battery charger
  Solution: make sure battery is connected, the key switch is on, and the brake override circuit is in the run position; also test your battery charger and motor controller and replace any nonworking parts

• Dash display: no LEDs or LCDs on
  Condition: forklift functions as normal
  Cause:  open connection between display and controller, defective display, or defective LEDs
  Solution: make sure harnesses are connected at MDI and connector B on controller; test the dash display by connecting a handset to it and testing for communication; test LEDs by disconnecting them, connecting the handset, and testing the handset; replace any nonworking parts

• Dash display: no LEDs or LCDs on
  Condition: forklift functions as normal
  Cause:  Because this condition is similar to the last, it will take a handset to determine its cause. If the handset displays “NO COMMUNICATION,” the controller is defective.
  Solution: replace controller

• Dash display: no alarm
  Condition:  traction and hydraulic functions not working
  Cause: improper startup sequence by jack operator
  Solution: check brake switch, accelerator, steer handle, and hydraulic inputs

• Dash display: AL66
  Condition: hydraulic function not working
  Cause: battery voltage is low or controller voltage calibration is incorrect
  Solution: charge or replace battery; otherwise, use handset to determine the voltage read by the controller and compare it to an actual voltmeter reading; replace controller if the two readings differ by more than 1.5 volts

• Dash display: AL99
  Condition: traction and hydraulic functions not working
  Cause: incorrect battery selected, damaged battery, or damaged connection to batter
  Solution: check that you have the right voltage for your truck, manually check the voltage of your battery, inspect it for any damage, and check its connecting crimps and cables for damage as well

• Dash display: AL01
  Condition:  traction and hoist functions not working
  Cause: control card throttle or lift/lower calibration is out of range; control card is damaged or defective
  Solution: use the tester function on a handset to see if either calibration is greater than 1 volt at neutral; replace control card if damaged or defective, which can be checked by seeing if both “forward switch” and “backward switch” are on at the same time when testing

• Dash display: AL01
  Condition: traction and hoist functions not working
  Cause: incomplete connection between control card and controller; traction reversing switch not connected; damaged or defective tiller card
  Solution: check connections between control card and controller; use a handset to test for operation of traction reversing switch; replace control card if tiller card is damaged

• Dash display: AL02
  Condition: traction and hydraulic functions not working
  Cause: main contactor tips are welded closed or motor field circuit is broken
  Solution: disconnect power leads at contactor and test for an open circuit; check connections between motor field and controller

• Dash display: AL4
  Condition: traction and hydraulic functions not working
  Cause: damaged connection to lowering valve; damaged lowering coil or lowering valve cartridge
  Solution: check electrical connection between valve coil and controller; check lowering valve coil for resistance, replace if not approximately 17.7 ohms; replace lowering valve cartridge if necessary

• Dash display: AL5
  Condition: traction and hydraulic functions not working
  Cause: damaged connection to brake or brake coil damaged
  Solution: check connection between electric brake and controller; check brake coil for resistance in both directions and replace if not between 27.36 and 30.24 ohms

• Dash display: AL6
  Condition: traction and hydraulic functions not working
  Cause: damaged connection to traction motor; traction motor armature resistance is too low; field wires are loose or damaged; motor field winding is shorted or too low
  Solution: check electrical connection between traction motor, field wires, and controller; check traction motor armature for shorts; check motor field resistance and correct if not between 0.5 and 1.5 ohms; check contactor coil for resistance of 52 ohms

• Dash display: AL7
  Condition: traction functions reduced below 14°F or above 167°F and not working above 194°F
  Cause: controller temperature is too hot or cold; controller temperature is not calibrated correctly; controller sensor or controller itself is damaged
  Solution: move truck to a warmer or cooler location; use a handset to check that controller temperature matches room temperature (if not, replace controller)

• Dash display: AL8
  Condition: traction and hydraulic functions not working
  Cause: over current in driven component
  Solution: check main harness for damaged connections to main contactor, brake, and electric valve coils; check contactor, brake, and electric valve coils for correct resistance (52 ohms for contactor, between 27.36 and 30.24 ohms for brake coil, and 17.7 ohms for electric valve coils)

• Dash display: AL10
  Condition: traction and hydraulic functions not working
  Cause: controller is damaged; damaged wire connection; short circuit in harness; ground between motor windings and chassis; motor field winding is shorted to chassis; field current driver circuit has failed; watchdog hardware circuit is damaged
  Solution: cycle key switch off and on and replace controller if problem not solved; check wire connections at contactor, pump motor, and traction motor; check main harness for shorts; check for grounds or shorts between motor windings and chassis; check motor field resistance (should be about 1.5 ohms); measure voltage between F1 and B- and F2 and B- on field current driver (should be half the voltage between B+ and B-)

• Dash display: AL94
  Condition: traction and hydraulic functions not working for one minute
  Cause: no fault is occurring – the controller is installing hour meter memory from MDI display if controller has been replaced
  Solution: no solution needed; truck will operate as soon as data transfer is complete

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