Tech Tips

The Skyjack full-size rough terrain scissor lift models 8831/8841 and 9250 offer single or dual hydraulic extension decks as an option. These optional hydraulically powered decks extend and retract using a cylinder and hydraulic power pack mounted under the platform and operated from a small control box located on the main platform. When the key/selector switch on the main control box is positioned in the LIFT mode, the power extend deck circuit is enabled, allowing power extension deck operation.

The deck extension cylinder is a single acting cylinder mounted under the platform and connected to the main and extension decks. The hydraulic power unit is a self-contained motor/tank/pump and valve assembly mounted under the main deck. Power for the pump motor is taken from the main battery in the base cabinet and that 12 volts is sent to the power unit’s solenoid from a contactor near the main battery. Power connections for the circuit are found at a small circuit card near the power unit under the platform.

As with any extendable platform, keeping the main platform floor and the extendable deck clean and clear of debris will ensure the deck can move in and out freely. If you experience a problem with the deck extending or retracting, inspect the area for debris and any damaged or loose parts which may impede the deck movement. Any bent platform structure on the main and extension platform will prevent the proper operation of the deck. Consult the correct manual for the serial number of the machine you are working on for specific electrical and hydraulic circuit information when troubleshooting the function.

If you need technical assistance with this feature or have any questions regarding your Skyjack product, please contact Skyjack Product Support at 1-800-275-9522 or email service@skyjack.com.

When testing electrical circuits, we suggest testing the circuit with system voltage (operating the function) rather than performing a continuity test. The reason for this is that most bad connections or components can support or carry the power of the 9-volt battery in your volt meter; but when system voltage is applied to the circuit the connection fails. Therefore, testing using continuity will likely give you an invalid and inaccurate test result which will have you chasing your tail instead of making progress to find the cause of the problem.

The Skyjack telescoping and articulating boomlift models use a cable carrier assembly (commonly referred to as a cat-trac or e-chain) to house the electrical and hydraulic hoses that run from the turret to the platform. This cable carrier is mounted on one or both sides of the boom and rolls in and out with the boom as it is extended and retracted. It protects the cables and hoses inside and prevents them from getting tangled with each other.

Each section of the cable carrier is called a link; each link attaches to the next link and so on to form a complete assembly by simply snapping them together. The links are connected across the top and bottom of the opening by crossbars which snap into tabs on each link. Some of the cable carriers that Skyjack uses have lids which snap onto the crossbars and covers the opening between the sides of the links. The end links are called mounting brackets and allow the assembly to be fastened to brackets at each end. Figure 1 shows a cable carrier assembly and its parts.

The design of this component allows any damaged parts to be replaced easily without having to remove and reinstall the hoses and cables from the cable carrier. The repairs can be done with the e-chain on the machine – no need to remove it. The lids and crossbars are removed easily with a thin-blade screwdriver. Simply insert the screwdriver blade into the slot in the lid or crossbar and pry up gently to release the part as in Figure 2.

The correct parts manual for the serial number of the unit you are working on will have the correct cable carrier parts listed. The cable carrier is manufactured by IGUS (named System E4/4 Energy Chain) and more information including assembly/disassembly instructions and videos are available at their website www.igus.com.

If you have any questions regarding any Skyjack product, please contact Skyjack Product Support at 1-800-275-9522 or email service@skyjack.com.

When you are troubleshooting a problem, make sure to try and operate all the functions and note which functions do not operate. Many functions use common electrical or hydraulic circuits and knowing what operates and what does not can help narrow down the search for the cause of the failure. For example, an electric scissor that has no right steer when static (not driving) may operate steer right when driving forward or reverse. Taking a moment to operate all the functions can eliminate a part of the electrical and hydraulic circuit that we know operates the steer right function and narrow down the list of potential causes to solve the problem quickly and accurately.

The joystick controllers used on the Skyjack SJIII Compact and Conventional scissor lifts, the SJ12/16 Mast lifts, and the Rough Terrain scissor lifts have incorporated a change to the enable circuit of the joystick. You may notice this change when you are troubleshooting the machine. Once the enable trigger is squeezed, an internal timer starts running; if a function is not operated within 7 seconds, the enable circuit is shut off and the joystick trigger must be released and depressed again to reset the enable circuit. The 7 second cut-out is used to inhibit tampering with or bypassing the enable switch with tape, a zip tie, or other means.

To avoid the 7 second cut-out while trying to diagnose or troubleshoot the machine function, always make sure that the joystick enable is not held on continuously.

You can identify the joystick with the 7 second cut-out by checking for the cut-out function or by the part number (see table below).

The part number will be on the side of the joystick frame inside the control box. These joysticks with this functionality have been used in production since March 2012, and sold by Skyjack parts department since August 2012.

If you have any questions regarding your Skyjack product, please contact Skyjack Product Support at 1-800-275-9522 or e-mail service@skyjack.com

When troubleshooting a no or low voltage output problem on a generator, make sure the generator to pump coupling is tight. Generator rpm is essential to correct generator voltage output. 
Both the gen and pump shafts may appear to be turning at the same speed, but the generator may be spinning slower due to the coupler being loose at either shaft.

The new style hydraulic pumps used on the Skyjack Compact and Conventional model electric scissor lifts mount to the pump motor with two socket head cap screws. You will see four cap screws at the front face of the pump. Two of the cap screws hold the pump body together, and the other two cap screws secure the pump to the motor face plate. To remove the pump, you need only to remove the mounting cap screws that are missing from figure 1. Do not remove the pump body screws shown in figure 1, as this may cause the pump body to come apart. Figure 2 shows the ‘tang’ style pump drive coupling that engages the pump to the motor shaft.

When replacing this pump, apply a small amount of grease to the tang of the pump and the cavity on the motor shaft before mating it to the motor. If the pump does not fit cleanly and fully onto the motor, the motor may be wrong for that pump. Do not use the bolts to draw the pump to the motor as this may damage the pump. Once the pump is properly fit to the motor, install the mounting screws and tighten to 230 in-lbs (26Nm).

When ordering a replacement part, use the service or parts manual for the serial number of the unit you are servicing. Do not use a pump that is not specified for your machine’s serial number. The service and parts manuals are available at our website, www.skyjack.com and printed and digital copies are available from our parts department. If you have any questions regarding your Skyjack product, please contact Skyjack Product Support at 1-800-275-9522 or email service@skyjack.com.

TECH TIDBIT

The Skyjack VR model telehandlers are now equipped with the Tier 4 interim diesel engines from Cummins. The only noticeable changes are the additional parts for the engine and the air cleaner is now located outside the engine compartment under where the boom pivots. Also, the engine harness and related relays at the engine have been relocated to atop the engine bellhousing for easier access.

There are 3 types of tilt switches used on Skyjack aerial work platforms. Figure 1 shows the older style tilt switch with the spring mounted switch body and bubble level on top. This type of switch is used on older model boom lifts and both electric powered scissor lifts and engine powered rough terrain scissor lifts. Figure 2 shows the current style tilt switch – the ‘black box’ type which is now used instead of the type in Figure 1. Figure 3 shows the auto level module which has the tilt switch built-in and is used on the rough terrain scissor lifts that are equipped with automatic levelling outriggers.

In order for the tilt switch to effectively do its job, it must be calibrated after it is installed. If the tilt switch is not calibrated correctly, the tilt switch circuit will not sound an alarm and/or cut out functions at the correct angle. To calibrate the tilt switch, first make sure the machine frame is level. Once the frame is level, you can set the tilt switch to match. For the type of tilt switch in Figure 1, adjust the nylon lock nuts on the tilt switch base to place the bubble in the center circle. The tilt switch types in Figure 2 and Figure 3 are set electronically using the procedure provided with the switch or in the correct service manual for the model and serial number of the lift you are working on.

Remember, all three types require the machine frame to be level before calibrating. The calibration process must be performed each time a tilt switch is installed on a machine. If the tilt switch mounting bracket is adjusted for any reason, the tilt switch must be recalibrated after the bracket adjustment.

To ensure that you are using the most up-to-date service and parts information available, the service and parts manuals are available online at www.skyjack.com  Please use the manual for the model and serial number of the unit you are servicing. If you have any questions regarding the tilt switches or any part of your Skyjack product, please contact Skyjack Product Support at 1-800-275-9522 or email service@skyjack.com

IMPORTANT DATES TO REMEMBER

JULY 14, 15, 16, 17, and 18th 2014
DURING THIS WEEK THE SKYJACK TECHNICAL SUPPORT STAFF WILL BE INVOLVED IN OUR ANNUAL TRAINING SEMINAR.

Monday JULY 14TH, Tuesday 15th, Wednesday 16th, & Thursday 17th
TELEPHONE ACCESS TO ALL OF OUR TECHNICAL STAFF WILL BE VERY LIMITED DUE TO THESE TRAINING CLASSES. HOWEVER, WE WILL TRY TO RETURN CALLS AS QUICKLY AS POSSIBLE.

FRIDAY JULY 18TH, NORMAL ACCESS WILL RESUME.

TECHNICAL INFORMATION IS ALWAYS AVAILABLE AT www.skyjack.com

**THE PARTS DEPARTMENT WILL NOT BE AFFECTED **

WE APPRECIATE YOUR PATIENCE DURING THESE FEW DAYS.
THIS TIME ALLOWS US TO WORK TOGETHER TO PROVIDE THE HIGH LEVEL OF TECHNICAL SUPPORT THAT OUR CUSTOMERS HAVE COME TO EXPECT.

Figure 1 shows the outrigger weldment and cylinder assemblies. The weldment attachment bolts "A" should be inspected regularly for any problems and should be properly torqued to the correct specification.

The outrigger cylinder assemblies should also be checked at the same time for any problems and to ensure that their bolts are tight.

It is important to make sure that all the fasteners on every machine are tightened properly. If not maintained regularly, loose fasteners on the outrigger attachment connections may lead to damage to the outrigger cylinder assemblies, outrigger weldment, and/or the machine base frame, resulting in the need for replacement.

To ensure that you have the most up-to-date service information available, the Skyjack service and parts manuals are accessible online at www.skyjack.com or from our parts department. Please use the correct manual for the serial number of the unit you are working on. If you have questions regarding your Skyjack product, please contact Skyjack Technical Support at 1-800-275-9522 or email service@skyjack.com.