Control Boards and Flash Code Diagnostics


Here is a very interesting statistic for you — One of the components usually at the top of warranty claims for any manufacturer is control boards. A large percentage (typically 50 – 70%) of control boards tested result in “No Fault Found” (NFF). Why do you think this happens?

You would think with the introduction of “flash code diagnostics” on control boards that the opposite would be true — very few control boards at the top of manufacturer’s warranty claim lists — but that’s not the case and the opening statement is TRUE!  Case in point —later this morning I am going out to meet a tech at a job site where the company has replaced 3 of the same control boards in the first 7 months since the unit was installed — what do you think the odds of that happening are?  Do you think this adds to the above statistic?  Let’s look a some things to consider when dealing with control boards.

Flash code diagnostics were added to controls to help the tech in the field find the problem quicker. In a cause and effect world — they are the effect of a problem encountered with the unit or piece of  equipment. They were not intended to be the “end all” for job site diagnostics. Let’s look at a few examples. A tech arrives on the site and finds a unit “locked out” on a flash code that says high pressure switch tripped.  He recycles the power to the unit and it starts so it must be a bad board. He replaces it and, lo and behold, the new one does the same thing.  Now if he’s smart, he is going to find out why the high pressure switch is tripping this time.  Or  there is a flash code that says the heating is locked out– except he’s in cooling and because the heat lock out flash code is there — cooling is locked out.  This HAS TO BE A BAD BOARD –right?

The whole point I’m trying to make here is board flash code diagnostics are just there to get the tech started in the right direction.  They ARE NOT the actual diagnosis.  Yes, the high pressure switch tripped but what caused it to trip — not the board — but dirty coils, bad condenser fan motor or capacitor, etc.  The diagnostic flash codes are there to give the tech the RESULT of a malfunction –not the cause.  Same thing with a heating flash code — all that says is there is a problem in the heating section and that needs to be found.

When you look at today’s control basic boards, there can be as many as 14 or 15 different flash codes available to the tech — some are just statuses and some are problems. On more sophisticated controls, there can be 22 or more flash codes.   The good techs use these to find the cause of the problem — and usually it is not the board.  These are not 14 or 22 or more reasons to replace the board as a lot of techs think.  These are 14 or 22 or more possible problems the board can detect and let the tech know about.

Of course boards can fail. When you see water on a board or burn marks on boards, you can be pretty sure that board has failed but boards should be the LAST COMPONENT replaced when diagnosing a problem. Of course, even in the case of a wet or burned board — why is the board wet? — where is the water coming from? — what caused the board to “burn”  — voltage problem?– loose connection?  Those also are “diagnostics” that need to be examined to prevent problems. All of the flash codes and all of the board “conditions” are there to give the tech direction. The great techs will use these to make the proper and correct diagnosis based on flash codes, pressures, voltages, meters, gauges, appearance and  ultimately –their own EXPERTISE and KNOWLEDGE.

Let’s see if we can reverse that opening statistic of 50 -70% of boards being returned with “no fault found”.  If we do the proper diagnostic, make use of the flash codes or information provided by the manufacturer, and above all, ATTEND MANUFACTURER’S TRAINING so you better understand what the manufacturer is trying to  do  and tell you with their various flash codes, I can assure you that statistic will be reversed. As I said in one of my previous posts, we all need to keep learning and are “practitioners of HVACR”. If we develop good habits and make proper use of the information at hand — then –“practice will make perfect” and fewer board will be replaced.

By the way — one last thing to think about — did you notice that I never said board fault codes and always said flash codes? The words board fault code automatically give some techs the idea that the board is at fault. By just changing our thinking and using the term flash code diagnostics, we can now approach these as helpers for us to use. I suggest everyone get into this mind set and that too, will help eliminate boards being replace with NFF.

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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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2 Responses to Control Boards and Flash Code Diagnostics

  1. Walter Wall says:

    My furnace has a CES0110057-02 control board and the LED is blinking 2 short and 1 long. Can you tell me what this means??? My furnace is cycling but not going to full fire mode!!!

    • What is the make and model of your furnace? Different manufacturers use different boards with different flash codes.
      It is usually best to contact the tech support of the manufacturer of your equipment.

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