How do you test an oil furnace transformer?

To test an oil furnace transformer, first ensure safety by disconnecting power. Then, using a multimeter set to AC voltage, measure the input and output voltage across the transformer terminals. Verify that the input matches the voltage rating specified on the transformer and that the output is consistent with the furnace requirements. Additionally, inspect for any physical signs of damage, such as burns or corrosion, and listen for unusual noises during operation. If the readings are outside the expected range or abnormalities are detected, it may indicate the need for oil furnace transformer replacement to ensure proper function and safety in your heating system.