Ohm My


One of the most common mistakes I hear techs make is confusing zero ohms with infinite ohms. The fuse above is showing near-zero ohms, which indicates a good electrical path with very little resistance.

If there is a perfect path, it would have zero ohms (which isn't actually possible unless you happen to be testing a superconductor).

If there is no path, the circuit has infinite ohms. That would show up as Open, OL, or something similar.

When I ask what ohm reading a technician is getting, they will often say “none.” None could easily mean zero or infinite, so it's important to clarify.

Once again:

Zero ohms = shorted/closed/directly connected

Infinite ohms = open/no path

Try to remember to say either infinite or zero instead of  “no ohms” or “none” to avoid confusion.




To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from