How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
Why has the thermostat screen gone blank?
Friday, June 22, 2018
A digital thermostat can be powered by either batteries or the house electrical system. Pull the front plate of the thermostat and look for batteries behind it. They are usually AA or AAA batteries, and replace them to see if that fixes the problem. Also, check the connection points for corrosion because, if old batteries have been left in the thermostat, they might have corroded the connections to the point where they will not make a good contact with new batteries. Sanding off the rust with a nail file may help.
If there are no batteries in the thermostat, then it is not getting power through the electrical wiring of the HVAC system. Check the circuit breakers at the electric panel, and also the disconnect boxes at both the indoor and outdoor units. It is not unusual at foreclosed or abandoned houses for the the pull-disconnect plug to be missing.
Still no luck? It may be a thermostat wiring connection problem, wiring damaged by a grass trimmer near the outdoor unit, or the thermostat may have simply gone bad and needs replacement. These possibilities need to be checked by a technician, and further evaluation by a licensed HVAC contractor is the next step.
Oops, almost forgot! There is one more possible solution if you have a combination gas furnace and electric air conditioner, and have recently replaced the air filter. Did you have to remove the bottom panel of your furnace/air handler to change the filter behind it? There is a safety switch along the top of the panel opening that shuts off both the system and the digital thermostat when the panel has been removed or is loose. Check to make sure that the panel is securely back in place so that the switch is not activated. The switch can be a lever-type, like the one shown below, or a pop-out button.
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To learn more about heating and air conditioning systems, see these other blog posts:
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