Using an ohmmeter, what test results would indicate an inoperable block heater?

An inoperable block heater will typically show infinite resistance between both heater terminals when tested with an ohmmeter. This result indicates that there is an open circuit within the heater element, meaning that electrical current cannot flow through it.

When the block heater is functioning properly, you would expect to see a low resistance value reflecting the continuity of the heating element, which allows current to pass through. Infinite resistance signifies that there is a break in the element or a complete malfunction, preventing it from heating the engine block.

The other options represent different scenarios: continuity between both heater terminals would suggest the heater is operational; no continuity between either terminal and ground implies the heater is isolated from the chassis, typically a good condition; and infinite resistance between either terminal and ground suggests a good insulation but does not provide information on the operational state of the heater element itself. Therefore, infinite resistance directly between the heater terminals is indeed the indicator of failure.