Recently, we successfully completed a customer’s call for thermostat issue. Our customer’s home is roughly 25 years old and they had a new HVAC unit installed 4 years ago and a newer thermostat installed prior in 2018.
Our customer’s initial complaint was that their thermostat seemed to be eating batteries. The unit would still power the heating and cooling, but all features such as wifi, interface sound and app syncing stopped working. They went through 5 batteries in a span of a month. Assuming they needed to replace the thermostat, they purchased a new one and upon installation received an error message that the thermostat was not receiving power fed by the red wire, which is also known as your (hot) power line to the furnace.
Upon inspection, we first started with the basics to rule out anything obvious. Power from the breaker switch at the main panel was turned on and then off and confirmed working.
We then tested power readings and levels at the transformer. The transformer’s job is to take the 220V coming off of your main panel and convert it to 110v. All readings coming in and out of the transformer were normal, including reading 27V at the circuit board.
On the board is where the thermostat wires connect to, with each wire representing a specific responsibility. (Heat, AC, Fan Blower, Power and the Common wire). All levels were normal at these terminals.
Next, we moved to the actual thermostat wiring at the wall. We first started by reading the volts to both common and power wires. We found normal voltage on the common wire, but only 9V to the red wire/hot.
Therefore, upon initial diagnosis, we determined that there was a short somewhere between the furnace and the thermostat in that wire. Before choosing to replace the entire wire bundle, we wanted to inspect the crawl space to see if we can find anything obvious.
And boy, did we find something. What we found was a previously spliced wiring bundle that had been replaced at some time in the past. Instead of securely joining each wire with the proper electrical wing-nuts, some one used the ole “electrical tape special” to sloppily join the red wire, which seemed to lose connectivity for obvious reasons. Even more interesting, the common blue wire was completely disconnected.
We did the right thing by using wing nuts to properly secure each wire and retested voltage at the thermostat. All readings were now normal and we knew we had proper power.
Next, we booted up the thermostat, which then showed the battery at the proper levels, however wifi and other features were still not working. We concluded that the thermostat was also bad, in conjunction with a short in the actual wiring beneath the customer’s home.
Customer installed a new unit and has had no issues since. Sometimes in HVAC diagnosing, there can be more than one issue going on, but when an initial complaint is brought up, it might appear as one cause.
Here at Gem Heating & Air Conditioning of Boise, Idaho we pride ourselves on delivering exceptional service mixed with honesty. We know that as a homeowner or business owner, you rely on experts to keep your living area comfortable with heating & air conditioning all year around. We also perform maintenance on water heaters, as well as new water heater installation too.
Contact us today for quick and reliable HVAC service in the Treasure Valley!
