Have you worked on the new 20, 21, and 23 SEER2 units and encountered a fault code 25-XX (for example, 25-61)?
Fault code 25 indicates an invalid model plug. On the newer units, however, it can mean more than just a missing model plug. “Invalid model” may indicate that the unit does not recognize what it is, or that it believes it is a different capacity or type than it actually is—for example, a 3-ton AC being identified as a 5-ton heat pump. This fault will be displayed on the PCM (Primary Control Module), which is the main control board for the unit.
The fault consists of a main code (25) and a subcode (such as 61). Common model-related fault codes include 25-24, 25-61, 25-62, and 25-63.
These new units do not require or use model plugs from the factory. They are programmed at the factory with the correct model and serial number. A model plug is only needed if you are replacing a PCM or if the board has lost its programming.
So what if you don’t have a model plug? Here’s a useful trick.
In the Technical Service Group, we have seen both brand-new units that didn’t recognize themselves out of the box and existing units that lost their model information, but the technician does not have a model plug on hand. In this case, you can use the DIP switches to reidentify the unit.
With power on, turn DIP switch number 4 on. The PCM will detect the size of the VFD and begin scrolling available unit sizes on the 5×7 dot matrix display. For example, on a 3-ton heat pump, it will scroll “36K AC” and then “36K HP.” When “36K HP” appears, turn DIP switch number 4 off and power-cycle the unit. This will lock in the correct BTU and type of unit.
When power is restored, the display will show “36K HP” for approximately two minutes, confirming the setting has locked in.
For any questions regarding this process, you can refer to the unit’s Service Manual, or contact the Technical Services Group for further guidance.
Below is an example of the guidance you may find in the service manual.
Disclaimer: The technical statements, information and recommendations contained herein are believed to be accurate as of the date hereof, but Mingledorff’s does not make representations or warranties, express or implied, as to its accuracy, its completeness, or the results to be obtained. The information is being provided for informational purposes only and is intended for use by persons having adequate skill and expertise regarding the proper selection, use and application of the products and recommendations and at their own risk and discretion.
Installing heating, ventilation, and air conditioning (HVAC) systems require precision, knowledge, and attention to detail. While many technicians rely on
Imagine that you receive a call from a customer stating that their heat is not working. Upon inspection you find
Most gas furnaces have several safety limits, main limits, roll-outs, 80%’s will have a DSS (Daft Safety Switch) These safety