Carrier Supra 950MT Operation & Service Manual

Also see for SUPRA 950Mt: Operation and service manual Operator's manual

5-23 62-118635.18 MICROPROCESSORNOTEThe software revision level is noted on a label located on the EPROM chip (component U3 on themicroprocessor logic board). Under NO circumstances should this label be removed.CAUTION!Under no circumstances should a technician electrically probe the processor at any point,other than the connector terminals where the harness attaches. Microprocessor componentsoperate at different voltage levels and at extremely low current levels. Improper use of voltme-ters, jumper wires, continuity testers, etc. could permanently damage the processor.Microprocessor InputsSome microprocessor inputs operate at voltage levels other than the conventional 12 VDC. Connector points and theassociated approximate voltage levels are listed below for reference only. Under no circumstances should 12 VDC beapplied at these connection points.Grounded wrist cuffs are available from Carrier (P/N 07-00304-00). It is recommended that these be worn when-ever handling a microprocessor.Most electronic components are susceptible to damage caused by electrical static discharge (ESD). In certaincases, the human body can have enough static electricity to cause resultant damage to the components by touch.This is especially true of the integrated circuits found on the truck/trailer microprocessor.ESD SafetyAlthough there is less danger of electrical static discharge (ESD) damage in the outdoor environment, where theprocessor is likely to be handled, proper board handling techniques should always be stressed. Boards shouldalways be handled by their edges in much the same way one would handle a photograph. This not only precludesthe possibility of ESD damage, but also lowers the possibility of physical damage to the electronic components.Although the microprocessor boards are fairly rugged when assembled, they are more fragile when separated andshould always be handled carefully.When welding is required on the unit frame or on the front area of the trailer, ALL wiring to the microprocessorMUST be disconnected. When welding is performed on other areas of the trailer, the welder ground connectionMUST be in close proximity to the area being welded. It is also a good practice to remove both battery cablesbefore welding on either the unit frame or the truck to prevent possible damage to other components such as thealternator and voltage regulator.a Replacing the KeyboardShould damage to the keyboard of the microprocessor occur, it is possible to replace only the keyboard.b Hour MetersThe hour meter can be set to any value via the serial port if the meter has less then five hours on it. This allows areplacement microprocessor to be set to the same hours as the microprocessor it is replacing.The microprocessor has two programmable maintenance hour meters, which are set via the serial port. Thesemaintenance hour meters are compared to one of the hour meters (diesel, standby, or switch on). If the hour meteris greater than the maintenance hour meter, the proper service alarm is triggered.Table 5–6 Connection Point Voltage InputsConnection Point Approximate VoltageATS, CDT, RAS, SAS, WTS 2.5 vdc (Variable)MP23 5.0 vdc