Basic Electrical Troubleshooting or “How To Use Meters” (part1)

Since most of my postings are based on the phone calls I receive from “technicians” in the field or at job sites, I feel compelled to write this blog about basic Electrical Troubleshooting.

Let’s start with a few examples of the calls —

The other day I had a technician who was ready to condemn a 3-phase compressor because it would try to start and then trip the internal overload.  When I questioned him on his “power” to the compressor, he said it was good(?).  When I asked him what good was, he said he had 230 volts.  I asked how he checked it and he said, “I have 230 volts between all the terminals on the contactor”.  When I asked what he had from each terminal to ground it turns out, he was missing 1 leg of power due to a blown fuse.  He didn’t realize that he was reading a “back feed” through the windings on the “pairs”.  When he replaced the fuse, the compressor started and everything worked fine.

Then I had a technician call and he was getting a “fault code” saying a sensor was not compatible with the system.  I asked him what the ohm reading of the sensor was and he said 13.2 ohms. If this was truly the case, the sensor was bad but then I asked him what scale he was on?  He said, “my meter is auto-ranging”.  I asked if there was a K or M on the screen  and he said there was a K. Well, that means the sensor was actually reading 13,200 ohms which was a good sensor. All we had to do was re-boot the control to find the sensor since they initially started the system without the sensor and then added it afterwards and never powered down so the system looked for the sensor. This was the second sensor the technician put on the system and he was ready to condemn it also.

I use these examples to make the point that knowledge of how to properly use meters is very important to do proper diagnostics. I do carry a digital multimeter but I still carry an analog meter with selectable scales on it. They are also nice for checking a safety that “bounces” because I can watch the needle move where most digital meters don’t react quick enough.  I know most guys look in wonder when I bring it out, but once I show them what it can do, and suggest they go buy a cheapo $10.00 Radio Shack analog meter, they usually do. (I grew up using a Simpson 260 and will never get rid of my analog meter).

In my next few postings, I will try to discuss how to properly use meters to make proper diagnostics. 

I’m not intending to insult anyone with this basic knowledge but I see there is a need for this.  Hopefully, you will not be offended by these posts and maybe remember something you learned in school that you may have forgotten.  I hope you take the time to read the next few posts on this subject.


About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
This entry was posted in Commentary. Bookmark the permalink.

2 Responses to Basic Electrical Troubleshooting or “How To Use Meters” (part1)

  1. Dan Trachsel says:

    You were already my hero and now you demonstrate that you walk on water!

    Nicely done Travis. What do you do in your spare time, cure cancer?

    All joking aside, this is going to be a fun forum.


    • Good Morning Dan:
      Thank you for the comments on the information on the blog. I started this just over 1 year ago to try to help the York Central Branch dealer with general information. We have told all our dealers about this and have a hyper link to our Branch web site so dealers can easily access it.

      A lot of the people in corporate caught on to this along with a lot of distributors. Feel free to pass this on to any of your dealers, print it out and put it on your counter.
      Travis liked it so much he asked if he could create the APP for the site. As I said, I have no problems sharing this info with anyone. My reward is having people read it and helping them and I will continue to write it as long as there is interest and a need.

      Mike Bishop
      Regional Branch Service Manager
      York Central Branch — Chicago

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s