Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Temperature Gauge Calibration Test (1968-74)
When gauge is suspected of being out of calibration, having a fluctuating movement or high or low readings, both gauge and IVR must be tested simultaneously. This test is done on vehicle.
Test equipment consists of a 10 ohm resistor to check gauge calibration for correct high readings, and a 73 ohm resistor to check for correct low scale readings.
Disconnect lead from gauge at sender unit, connect resistor between gauge lead and ground. Turn ignition on. With the 10 ohm resistor the gauge should show a high reading. With the 73 ohm resistor the gauge should show a low reading.
If gauge does not perform as prescribed, replace IVR and retest. If gauge now (with new IVR) reads correctly problem is solved. If gauge is still out of calibration it is defective and must be replaced.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.