Keep It Simple Servicer


I guess air conditioning season is upon us because I got my first call of the season from down state Illinois (it’s warmer there than in the north right now I guess) on an air conditioning problem.

However, in this case, it was and was not an actual cooling problem. The home owner turned on their air conditioner  and found that the furnace was running at the same time. Upon realizing this, they immediately turned off the switch on the furnace and called their service company for help.

Here is where this story gets interesting. You know from previous posts that I preach the K.I.S.S. (Keep It Simple Servicer) principle when it comes to diagnostics and servicing.  98% of the problem out there are usually something simple — right? I have talked about the 4 basics of a service call:

  1. KNOW WHAT IT SHOULD DO!
  2. FIND OUT WHAT IT’S NOT DOING!
  3. DON’T WORRY ABOUT WHAT ISN’T BROKEN!
  4. FIX WHAT IS BROKEN!

Well, this tech gets to the home, starts looking at things, and basically forgot the K.I.S.S. principle and the 4 basic rules of a service call. After he has been at the site for over an hour, changed the control board in the furnace, and did a bunch of other things, I get the phone call for help!

Now this poor guy is in a panic and is talking so fast I needed to first calm him down.  He is going on about both units running together and that he is getting 13 VAC at the control board on “W”  and other such voltages on “G” and the fan is running continuously.  He further goes on to say that he has the thermostat off the wall and still has this “strange voltages” at the furnace.

Once I got him calmed down, the first thing I asked was if he had tried removing the thermostat wires from the furnace control? He just said that he had the thermostat off the wall — why?  I convinced him to remove the thermostat wires off the furnace — ALL OF THEM!  Well, he finally did that and guess what — everything stopped.

I then told him to jump “R” to “W” to see if the furnace worked by itself. — Yep — sure did!  Then I had him jump “R” to “G” and the blower worked. Lastly, I asked him if he had an OHM meter? He said it was in his truck!  I told him to go get it.

He finally came back in and I had him ohm out the “R” wire to all the other thermostat wires since the thermostat was still off the wall and off the furnace board.  Low and behold — he was reading resistance between the wires — not a dead short — but some resistance none the less.  After some further investigation, he found that the thermostat wire behind the thermostat was wrapped around a nail and had been pulled so tight that it had compromised the insulation and “R” was just barely making to the other wires in the cable.  After pulling new wire — everything now worked as it should.

The point I want to make here is that he went looking for the “unusual” and turned a simple diagnostic into a major project and a new control board that wasn’t needed. We all need to remember the K.I.S.S. Principle and the 4 basic rules of a service call.

It is going to get even more interesting once we really start working again on the actual units and dealing with refrigerant again. Even here — remember that most of the problems with an air conditioner are EXTERNAL to the refrigerant side of a system.  the only thing that can go wrong on the refrigerant side of a system is OVER-CHARGE, UNDER-CHARGE, AND NON-CONDENSIBLES. All the other problems are caused by something else and we need to remember to absolutely follow the K.I.S.S. Principle when it comes to things like this.

[maybe now we’ll actually get some warm weather since I wrote my first post of this air conditioning season :>)]

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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
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