For 120V, Test yellow-to-black, yellow-to-ground, and black-to-ground. Verify proper ohms (within 10-15% of the value stated on the product label) across yellow-to-black, and no ohms for both yellow-to-ground and black-to-ground.
For 240V, Test red to black, red to ground, black to ground. Verify proper ohms (within 10-15% of the value stated on the product label) across red to black, and no ohms for both red to ground and black-to-ground.
For most products (under 200 ohms) set the DIGITAL, NON-SELF-RANGING meter to the 200 ohm range. Some heaters may require testing over 200 ohms, for these, set the meter to the 2000 (2k) range.
See instructions in attachment.