Resistance and Ohms

Jalen_Jalen2006

I’ve been told a bunch of different answers I want to completely understand. Checking resistance on motors whether single phase or 3 phase this happens to be single phase. I went across both leads GOT OL.( is it bad is it good) my mind says that’s bad. Went each lead to ground one lead read OL. The other read 17-20 MegaOhms to me motor is bad to my knowledge. What is short to ground? What is considered bad windings? Is OL ever ok? What do I look for when testing resistance on motors?

Jamie Hall

OL on most meters (read it as "open leads") means simply that the resistance is greater than the maximum reading possible on the meter — which is usually a completely open circuit. Which is fine, if that's what you want. 17 to 20 megohms to ground is alright.

To go back to a reading of "OL" across the leads to the motor (presumably the hot and neutral to a single phase motor). This is NOT good. The actual winding resistance, lead to lead, depends very much on the motor in question — a small motor may have 20 to 30 ohms winding resistance, but a big one may have only a fraction of an ohm. Resistance to ground should always be at least 10 megohms, and OL is better.

There is a definite "gotcha" on the "OL" reading, however: it may be that you have poor contact (or none!) on one test probe or the other. Make sure you have a very good connection and, if possible, test it.