Using a continuity tester to test wires

Old 07-11-18, 11:49 AM
Thread Starter
Join Date: Jun 2009
Location: USA
Posts: 61
Upvotes: 0
Received 0 Upvotes on 0 Posts
Using a continuity tester to test wires

A circuit shows "Fault" when a window is closed. When testing a window circuit by putting a continuity tester on the two wires in the panel, the line produces a tone when the window is closed as well as when open. Does that mean that the line is OK, and the sensor is broken? Or could it also mean that the alarm people couldn't find the wires in the wall (and the ends were twisted together in the wall) and they installed the sensor anyway.
Is there a way to distinguish between the two problems? 6 contacts don't work out of 20 in a 3 year old house. What are the odds?

We will be installing wireless contacts at those locations no matter what because it would do too much wall damage to replace the sensors. Just really curious.
Old 07-11-18, 12:06 PM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 27,979
Received 2,229 Upvotes on 1,988 Posts
If the tester shows the same thing when the window is both open and closed then something is not right. You can disconnect the sensor at the window and test it to verify if it is working properly. If it is then the problem is somewhere in the wiring between the sensor and panel.
Old 07-12-18, 09:41 AM
Join Date: Sep 2015
Location: US
Posts: 1,234
Received 209 Upvotes on 183 Posts
  1. Did you disconnect the wires before trying to check them? Leaving wires connected to the panel while testing produces false results.
  2. If this a true continuity tester, you can also get unreliable results if there is an End-of-Line resistor in the loop. Even an inexpensive analog Volt-Ohm Meter will provide more accurate results.

It's your money, but there may be an extremely inexpensive solution your problem.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: