BREATHER 3267288 - Caterpillar

To check the 8N2977 Converter Oil Temperature Gauge with a specific resistance instead of a sender, do the tests that follow:Connect +24 to 28 volts between the IGN and GND terminals.Connect 185 ohms (1 watt) between the SEND terminal and the ground (negative) of the power supply.After 5 minutes, the gauge must show a temperature at the last mark on the right hand side (160°C). Now connect 14,000 ohms (1 watt) resistance between the SEND terminal and the ground (negative) of the power supply. The gauge must show a temperature at the first mark on the left hand side (40°C).In these tests, the gauge must be in a vertical position. Cigar Lighter
Power for the cigar lighter circuit is from fuse 13 (on the schematic) with the identification CIGAR LIGHTER on the fuse and circuit breaker panel.
CIGAR LIGHTER CIRCUITCab Pressurizer
When the engine is in operation, the pressurizer circuit gets power from the alternator from the output side of the main power relay, and through a 30 amp circuit breaker. Power goes to the 1V6653 DPDT (double pole-double throw) toggle switch. The switch has a center OFF and two ON positions (LO-OFF-HI).When the switch is in the HI position, current is sent directly to the two pressurizer motors. When the switch is put in the LO position, current is sent through a 5L2854 Resistor. The resistor decreases the amount of current for the motors, and they operate at a slower speed.
CAB PRESSURIZER CIRCUIT
1V6653 SWITCH
PRESSURIZER MOTORS AND RESISTOR
1. Resistor. 2. Right hand pressurizer motor. 3. Pressurizer filter.Air Conditioner
The attachment air conditioner uses the same power circuit, pressurizer motor switch, and pressurizer (evaporator) motors as the cab pressurizer group. The air conditioner group adds the thermostat, the condenser motors, and the air conditioner compressor. When the pressurizer (fan) speed switch is in the HI or LO position, it sends current to the 3V253 Thermostat Switch. The thermostat has two different switches inside. When the thermostat is turned from the OFF position to any position between ON and COLD, one of its switches is always closed. This switch sends current to the coil of the air conditioner relay. This activates the relay which sends current to the condenser motors. The other switch in the thermostat, when it is closed, sends current to the clutch solenoid of the air conditioner compressor. This switch opens and closes according to the temperature, to keep the cab at the correct temperature. There is a receiver/dryer in the refrigerant lines which has a pressure switch. The pressure switch is in the air conditioner electrical circuit between the thermostat and the compressor clutch. The switch is closed when there is pressure in the refrigerant lines. If there is a loss of pressure, the switch opens and the compressor can not be activated. This is for the protection of the compressor.
RECEIVER/DRYER PRESSURE SWITCH
CONDENSER MOTORSDiodes
Several silicon diodes are used in the electrical system. The purpose of a diode is to permit the flow of current in one direction, but not in