SUPPORT AS 2327217 - Caterpillar

Illustration 1 g00277661
(1) Parking brake and secondary brake switch. (2) Retarder and service brake switch. (3) Switch (AETA).Some input signals to the Electronic Programmable Transmission Control (EPTC II) during a shift can cause a hunting condition of the transmission. A hunting condition is a rapid, unwanted transmission upshift or a rapid, unwanted transmission downshift that is caused by ground speed changes near a transmission shift point. An example of a hunting condition is repeated upshifts and downshifts by the machine.The EPTC II is designed to prevent a hunting condition. The EPTC II will perform a turnaround shift after every two seconds. A turnaround shift is a transmission upshift or a transmission downshift to the next speed position and then a shift by the transmission back to the original position.In normal operating conditions, a rapid shift may be necessary. An example of a normal operating condition is stopping the vehicle. If a rapid downshift is not made in this example, the engine will stop. Parking brake and secondary brake switch (1) will signal the EPTC II that rapid shifts are necessary. Parking brake and secondary brake switch (1) will open when the parking brakes or the secondary brakes are engaged.When parking brake and secondary brake switch (1) is open, the ground to the EPTC II is removed. The EPTC II will then determine that a rapid shift is necessary. Whenever the parking brakes or the secondary brakes are engaged, the EPTC II will shift rapidly.When parking brake and secondary brake switch (1) is closed, a ground to the EPTC II is created. The EPTC II then allows one turnaround shift.