1990 Ford Bronco Instrument Cluster Circuit Operation & Sender Specs (60-7)

This is page 60-7 of a Ford electrical/vacuum troubleshooting manual (EVTM) covering the Instrument Cluster circuit, uploaded as applying to a 1990 Ford Bronco. The page explains "How the Circuit Works": with the ignition switch in start or run, the gasoline and diesel engine gauges and indicators are powered by fuse 18 through the 640 (R/Y) wires. It describes the magnetic gauge design (coil, magnet, pointer) and gives key sender resistance specifications useful for diagnosis: the fuel sender reads 145 ohms with a full tank and 22.5 ohms empty; the coolant temperature sender reads 74 ohms cold and 9.7 ohms hot; the diesel coolant overheat switch closes at approximately 247°F. It explains the Oil Pressure Switch operation (closed under normal engine operation, open with engine off/no oil pressure), the Engine Warning Indicator module (lights on high coolant temperature or low oil pressure), the Tachometer (driven by ignition coil pulses on gasoline engines, by the Engine RPM Sensor on diesels), and the Voltmeter (indicates battery state of charge with the ignition in START or RUN). A boxed note directs readers to section 33-01 of the shop manual for further diagnostic information. This page is useful for testing fuel/temperature senders and understanding cluster gauge operation.