"FAULT OR FEATURE"
Electric lift trucks have advanced greatly from the carbon pile systems of the early vehicles. Electronics in general has made amazing leaps forward with smaller and smarter components. The new Electric Vehicle controls are now using small computer chips called microprocessors. With this new age electronics, system manufacturers can incorporate just about any requests for added vehicle features. Features sell trucks, but they also can manage to confuse the technician servicing that vehicle. Today's lift truck mechanics not only need to know the complete operating system, but they also must be able to distinguish between fault and feature.
"Directions won't pull in until I move the directional lever to neutral or the opposite direction, then the system operates as normal." Most of the seasoned technicians are aware that this is a built- in feature used in many of the systems today. Static Return to Off (SRO) or Static Return to Neutral (SRN) maybe classified as a safety feature. It requires the operator to return the direction lever to neutral anytime he leaves the truck and returns. During vehicle operation, if the seat or key switch is opened the control will shut off and cannot be restarted until the proper start-up sequence is accomplished. The start-up sequence requires the seat and key switch to be closed before the direction is selected. Even though it may sound obvious, this feature ensures that the operator knows what direction he will begin to travel, once the accelerator is depressed. This feature is standard in most newer controls but, unlike some features, it is not adjustable or programmable.
"I can't seem to adjust the time delay on my 1A/ bypass control. No matter how I adjust the potentiometer it always times out quickly." This is a common question relating to those controls which incorporate "Demand 1A" such as The General Electric EV-1 and early EV-100 controls. The 1A / bypass contactor is energized via the control card by two separate methods. The most familiar method is "Timed 1A", which is adjustable by a potentiometer on the control card. Typical "Timed 1A" adjustment range will be from one to eight seconds. The control card will also energize the 1A/bypass contactor on "Demand". Once the vehicle speed obtains aprox 85-90% of its top speed setting, 1A/bypass is energized by its "Demand 1A" feature. This "Demand" feature has no delay and overrides the "Timed 1A" setting. The purpose is to achieve the smoothest transition from SCR speed to 1A/bypass speed. Questions arise when the technician tries to adjust the "Timed 1A" with the drive wheels off the ground. In this situation, the vehicle will attain 85-90% speed very quickly, within 2-3 seconds, depending on the controlled acceleration rate setting. With the "Demand 1A" overriding any "Timed 1A" setting it always appears that the "Timed 1A" is not functioning. Unless the control system has a way to defeat the "Demand 1A" you should always adjust the "Timed 1A" with the vehicle on the ground. This feature has been eliminated on the newer EV100LX and ZX controls.
"When I lift my foot off the Accelerator pedal the opposite directional contactor energizes and then quickly drops out." I personally have fielded many technical phone calls on this one. This feature is very new and does appear to be a fault condition. The feature goes by several names but the most common is "Auto Plug Braking". Systems incorporating "Auto Plug Braking" will automatically reverse the directional contactors and cause the vehicle to plug brake, which reduces the speed, electronically, to near zero. This occurs whenever the directional switch or accelerator switch is opened. In the General Electric EV-100 Systems, this feature maybe programmed in or out via the handset or a program jumper mounted on the circuit board.
"When will the madness of all these new features stop?" Good question. Advances in electronics will continue and so will manufacturers' ability to control the forklift truck. Features definitely sell trucks but they can also make the vehicle easier to operate, last longer, and add safety for the operator and those around them. So remember to understand the systems completely, including those ever popular "selling features".