Oil Pressure & Coolant Temperature Gauges

Coolant temperature and oil pressure senders are located on engine and send current to gauges through 2 magnetic coils and a sender. Sender controls gauge pointer operation by monitoring current flowing through the coils. The oil pressure sender is connected to the junction of the 2 coils. It has low resistance when oil pressure is low and 90 ohms resistance when oil pressure is high.

The coolant temperature gauge has 1 coil grounded directly and the other grounded through coolant temperature switch/sender. The sender has 55 ohms resistance when coolant is at 260°F (127°C). Its resistance becomes greater at lower temperatures, approximately 1400 ohms at 100°F (38°C). This causes current through sender and 1 coil to increase as coolant temperature increases, thus moving the pointer.