1997/11/17 Caterpillar

RT50 (4XG1-UP) RT50SA (8DJ1-UP) RTC60 (5PF1-UP) RT60 (5DG1-UP) Telescopic Material Handlers

The joystick controllers on the telescopic material handlers may intermittently operate. This may result in the loss of one or more hydraulic functions. The function loss may often be restored by turning off the engine key switch and restarting the machine.

There could be several causes of the intermittent joystick operation. A problem with the battery, supply voltage wiring, electronic control box group, joystick, or mechanical problems could cause the intermittent joystick operation. The non-mechanical problems, trouble shooting, and some service procedures will be discussed.

BATTERY

Intermittent joystick operation may be caused by the battery voltage being too high or too low. Too high of battery voltage is caused when the machine is jump started with a 24 volt battery. Too low of battery voltage is caused when the battery is low on electrolyte.

Low voltage may occur in an older or poorly maintained battery that may suffer a severe drop in voltage after the machine is started. Once the machine is started, the voltage may recover after a short period as the charging system brings the voltage to the correct level.

The machine needs to have the key switch recycled, meaning the engine restarted, after the battery is fully charged and the machine is warmed up. This is done so the electronic control box group can detect the proper voltage at start up.

If a machine's battery is in a very deteriorated condition, a set of jumper cables is needed to assist in starting. The battery may be deteriorated and the weather or the engine condition is such that an extraordinary length of time is required to "crank" the engine before it starts.

The user needs to be aware of the above conditions and replace the battery. If the battery is not replaced, the machine operator must be prepared to restart the machine after it is warmed up and the battery is recharged.

Check the battery charging circuit. Pay particular attention to the 9S-0173 Circuit Breaker Assembly and the alternator indicator lamp for proper operation.

SUPPLY VOLTAGE WIRING

Early machines may have a 081-6169 Emergency Switch Harness or 083-8602 Stop Button Group installed behind the joystick controller on the right side cowl.

This button has been removed from production for some time due to its tendency to intermittently fail. If the machine in question has a stop button, remove it and then properly connect the three wires (blue 332, green 138, and pink 339). Cover the hole in the right side cowl with a suitable cover. The three wires provide power to the electronic control box group and the 098-5744 Valve (Dump Solenoid). The 098-5744 Valve is found only on early machines.

ELECTRONIC CONTROL BOX GROUP

The loss of hydraulics may be caused by the electronic control box group detecting a situation that could result in the hydraulics activating contrary to several programmed sequences. The electronic control box group has been designed to prevent the hydraulics from activating under certain situations. Some of the conditions that are protected against are:

1. The joystick may be intentionally or accidentally activated during the engine start up.

2. The operator may be applying too much force on the joystick controller which pulls it beyond the calibrated position for maximum activation.

3. The battery voltage is too high or too low.

4. There is an internal short circuit occurring in several components.

5. Occasionally, an abusive condition exists. This is detected by the presence of a broken stalk, a stalk that rotates freely, or a broken 8Q-5362 Disc.

Validate the power to the electronic control box group by checking the LEDs (Light Emitting Diodes) on the logic display. Refer to the section on fault indicator in Special Instruction SEHS6144 "Calibration Procedure and Fault Finding Guide for 081-5920 and 083-8141 Electronic Control Box Groups" for explanation of fault codes.

The electronic control box group must be removed from its storage position under the operator's seat support to view the fault LEDs. If there is neither a yellow, green, nor red LED energized with the key switch in the "ON" position, then the electronic control box group is not getting power. The electronic control box group must get electricity for the machine to have any hydraulic attachments to function.

Check the Sure-Seal connector that connects the joystick controller to the chassis wiring harness for moisture. Clean the connector using electrical contact cleaner. Do not use brake clean or any cleaner not specifically designed for use with electrical components. Seal the connection with the addition of 8T-9020 Grease. Make sure that the Sure-Seal clip is attached over the two connector halves.

During normal operation, the green and yellow LEDs are energized. If the green LED is energized and neither the yellow nor any red fault LEDs are energized, the problem may be in the internal relay.

The relay is located on a printed circuit board under the clear plastic cover located on the circuit board that comprises the electronic control box group. The cover to the electronic control box group must be removed to gain access to this relay. Occasionally, the contact tips on the relay may accumulate dust and fail to make contact.

To clean off the relay, wiggle the plastic cover off and clean between the contacts using a piece of clean paper about the thickness and texture of a business card. The above problems generally cause the loss of one function, proceed as follows:

1. Recheck the Sure-Seal connector for moisture.

2. Clean the connector using electrical contact cleaner. Do not use brake clean or any cleaner not specifically designed for use on electrical components.

3. Seal the connectors with the addition of 8T-9020 Grease. Make sure that the Sure-Seal clip is attached over the two connector halves.

If the problem is not related to the battery, supply voltage wiring, or the electronic control box group then isolate the problem using voltage checks. Start with the input volts to the electronic control box group from the joystick controller. Use a Caterpillar 6V-7070 Heavy Duty Multimeter Group or its equivalent for all tests.

JOYSTICK

The voltage reading coming from the joystick controller to the electronic control box group should be continuous. The reading should be approximately 0.4 volts at no activation and continuously read up to approximately 5 volts at full activation.

The test for joystick function can be performed with the controller removed from the machine using resistance (ohms).

Without activation, the indication should be an open circuit. There should be approximately 1000 ohms at initial activation. The readings should decrease continuously to approximately 210 ohms at full activation of the tested function.

Adjustment procedures for the various potentiometers are given in lift truck technical bulletins dated December, 1991, under the title "Service Parts Available for 083-8440 Joystick Controller Group, Procedure to Recalibrate the Joystick" (SMCS CODE 5485) and "Checking the 083-8440 Joystick Group" (SMCS Code 5485).

Disassembly of the joystick may be necessary at this point if the required readings are not obtained. Typical problems that may occur include:

1. Dirt is on the potentiometers. This interrupts the contact between the wiper and the potentiometers. A procedure to clean and lubricate the potentiometers is given later in this bulletin as "Servicing the Joystick".

2. The wiper is momentarily loosing contact with the potentiometer due to distorting of the wiper path. This is unique to the push buttons located in the head. This is typically caused by worn push buttons.

3. Wires going from the head and terminating at the 8Q-5362 Disc are broken. Ensure that the wires are long enough to endure the full activation of the stalk in both directions. Repair or replace the wires as necessary.

If the problem is not found, or if moisture is apparent upon disassembly, the problem may be moisture related. Service the joystick before taking any moisture related corrective action.

Servicing the joystick is recommended after the initial 100 hours of operation and at 500 hour intervals after the initial servicing. The servicing should be performed after the adjustment of the potentiometers and replacement of any needed parts.

Mark these additional service requirements in the Operation & Maintenance Manual (SEBU6390).

Service the joystick by removing the bottom cowl and joystick head as described in the reference bulletins.

Clean the potentiometers, various wipers and voltage rails with Tuner Control Cleaner & Lubricant. Carefully wipe off excess fluid with a cotton swab. If Tuner Control Cleaner & Lubricant cannot be found, clean the parts with benzene (lighter fluid).

Do not use electrical contact cleaner to clean the parts because it does not leave a lubricating film on the parts. The lack of a lubricating film will cause rapid potentiometer wear.

While performing the above cleaning and lubrication, gently rotate the potentiometer to slightly expose a slightly different wiper path on the potentiometer. Ensure that the exposed (non insulated) segment of the potentiometer windings are being wiped. Activate the functions to be sure that the engine connection is clean. Reassemble the joystick controller.

Before reinstalling the joystick into the machine, take the following steps to further waterproof the joystick:

1. Install a new 8I-5590 Cover (boot) that is available. This cover fits over the joystick controller head. This cover reduces the possibility of water and dirt getting past the push buttons into the controller head. This cover should be periodically inspected for holes, cracks, and wear and be replaced if necessary.

2. Tape the 083-8933 Boot that protects the existing wire harness at the bottom of the joystick controller to the joystick controller above the seam formed by the controller body and the lower cover. Use a waterproof tape.

3. Enlarge the hole in the cowl to 105 mm (4.12 in). This enlarged hole will facilitate the installation of the boot and joystick assembly through the cowl.

4. Make sure that 6R-9290 Clamp is snug and in place around the shaft and over the 6R-9290 Bellows (boot).

5. Apply 8T-9020 Grease as mentioned above.

Once the joystick controller has been serviced and reinstalled with the improvements, check the electro-hydraulic activation.

If the electronic control box group needs to be recalibrated, refer to Special Instruction SEHS6144 "Calibration Procedure and Fault Finding guide for 081-5920 and 083-8141 Electronic Control Box Groups".

It may be necessary to check the coils located on the end of the control valve for voltage and resistance. Resistance to each set of coils, such as tilt up, tilt down, should match at either 5.9 or 7.44 ohms.

The coils are marked on the ends to indicate ohms. If the voltage to these coils vary continuously with activation from 4 to approximately 9.5 to 10.5 volts, the function is not activating, and there are no additional fault codes, then the problem is mechanical (such as a stuck pilot valve or main valve, lines, or packing).