How to Interface into a Connector You Don’t Want to Pierce

[pre_ad postid=”7650″]By Joe Glassford. In this excerpt from Joe Glassford’s new Vehicle Testing Reference Guide Joe details a technique on how to easily test a wire without piercing it. Don’t want to pierce or cut wires, or if you have a completely molded connector where it seems impossible to get an acupuncture probe tool in for your testing try this out.

If you are reluctant to pierce of cut wires, or if you have a completely molded connector where it seems impossible to get an acupuncture probe tool in for your testing, you can do this: get any kind of stranded copper wire like the one shown in photo #1. This is a length of audio wire that has copper strands wound around one blue and one white stranded conductor. The more strands it has the finer the single strand will be. My wire has 40 strands. In photo #2 the blue and white conductors have been cut off. If you use a single piece of stranded wire this won’t be necessary, of course. Regardless of what type of stranded wire you use, you want to end up on one end of that wire with one single strand as shown in photo #3. Keep all strands intact at both ends. On the end with the single strand, just fold back the other strands as you may want to use another single strand when one you use gets broken. You are going to interface this single strand of wire into the female connector of whatever it is you are testing.

Photo #4 shows two pieces of wire with single strands out of one end. Each piece is being interfaced into the female terminal of the connector I am trying to test. Once you get the single strand deep into the female terminal, when the male terminals are inserted, you are interfacing as close to the load as possible.

Here I am looking at the voltage available to a bright headlight. One of my single strands is into the voltage feed side and one is into the ground side of this high beam connector. You may have to tape the wire in place to keep it inside the female terminal as shown in photo #5.

Once you have the single copper strands in place, taped to prevent them from coming out, plug the connector back into what ever it is you are testing, be it a light bulb connector, or an electronic control module. Once plugged back in, you can hook up your voltmeter to the other end of these wires (photo #6). At this end, you will connect your voltmeter probes to all of the strands of wire for the conductor you are using. This will pick up the single strand.

In my case, my source voltage was 14.3 volts once I started the vehicle. Turning on the high beams, my meter read as shown in photo #7: -13.50. Knowing that you can ignore polarity when doing voltage testing, I know that there is no significant voltage drop to the headlights on this vehicle. Maximum allowable is 1.5V.

With this set up, I could test the voltage drop on the feed side by placing my voltmeter positive (+) on the battery positive (+) terminal, and hooking my voltmeter negative (-) on the correct end of one of the wires I have interfaced. I could also test the voltage drop on the ground side by placing my positive (+) voltmeter probe on the end of the correct interface wire and placing my negative (-) voltmeter probe at the battery negative (-) terminal.

This is a pretty slick test for those times when you do not want to pierce wires or when you are dealing with molded connectors that cannot be back-probed. There will be times when this test will come in handy. I thought you would be interested is learning how it was done.[/pre_ad]