Switches & Instrument Panels: Testing: Gauges

Turn ignition on. If gauge needles do not move at all, check for blown fuse or broken power wire. If both gauges are inoperative, voltage regulator may be the cause. If only one gauge does not work, the gauge, sending unit, or connecting wiring may be at fault.
To test temperature gauge, disconnect sending unit wire. Connect a resistor between wire and ground, then check gauge reading. Change resistance and recheck. If gauge readings are as shown in tables, replace sending unit. If not, repair wiring or replace gauge.
To test fuel gauge, disconnect wire to sending unit at fuel tank (GLC Hatchback, RX7 and B2000) or unplug connector behind left kick panel (GLC Wagon and 626). Connect resistor between Yellow wire and ground. Check gauge reading.
NOTE: Allow 2 minutes for gauge reading to stabilize. It should be within 1 pointer width of line on gauge face. See Figure.
If gauge readings are incorrect, replace gauge. If readings are okay, test in-tank sending unit before replacing it. Resistance should measure 0-5 ohms with float raised, and 103-117 ohms with float lowered. If not, replace sending unit.

RESISTANCES FOR FUEL GAUGE TESTING

Needle Position

Test Resistor

Full Line

⁽¹⁾ 7 ohms

Half Tank

33 ohms

Empty Line

⁽²⁾ 95 ohms

⁽¹⁾	On GLC wagon and Pickup, 3 ohms.

⁽²⁾	On GLC wagon and Pickup, 110 ohms.

RESISTANCES FOR TEMPERATURE GAUGE TESTING