The Fan Won't Start on My Outside AC Unit You can troubleshoot many problems with an air conditioning unit yourself before having a technician make repairs. One problem that you may experience with your outside air conditioner is when the fan does not come on. This may indicate an electrical issue that will need to be fixed. To do this you will need to make a checklist of the electrical components to examine. Verify the switch on the thermostat is set to "Fan" or "Cool" and make sure the air conditioner is turned on. Check the temperature that has been set on the thermostat. This needs to be set below the current temperature of the room. Go to the circuit panel and see if a circuit has tripped or if a fuse has blown. Reset the circuit or replace a blown fuse. Examine the electrical wiring on the outside of the unit for damage. If the wiring is damaged or cut you will need to have it replaced. Take off the access panel and locate the condensate pump. Disconnect the drain line for the pump and make sure it is not clogged.

If the condensate pipe does not drain correctly the unit will not turn on. Locate the electric motor for the air conditioner and see if it has a reset button. Press the button down if it has kicked on. Inspectapedia: How to Diagnose & Repair an Air Conditioner that is Not Working Green-Energy-Efficient-Homes: Home Air Conditioning Problems If an inside air conditioning fan unit will not shut off, there are a few remedies. how to calculate hvac unit sizeIf your home air...ac unit not starting up My Air Conditioner Compressor Is Not Kicking On. best brand home ac unitsReasons That an Air Conditioner Will Not Come on. As the sweat trickles... If the compressor of the air conditioning won't turn on ... My Honeywell Thermostat Fan Won't Go On.

My Furnace Won't Start... Why Won't a Radiator Fan Turn On?. When this fan will not ... Radiator fans that don't come on pose a... Reasons Why the Fan Does Not Come on in a Central Heat and Air Unit. The blower fan on a car... The fan motor for an outside air-conditioning (AC) unit removes all the hot air inside the home and keeps ... If your air conditioner will not turn on, ... The Central Air Conditioning Fan Doesn't Turn On. Central air conditioning units usually... Why Central Air Conditioning Stops Working. The inner coil may freeze if your compressor runs but the evaporation fan ... When I Turn on the Air Conditioner the Fan Blows But the Outside... The Fan on My Air Conditioner Unit Does Not Spin How to Tell if a Fan Motor Is Broken on an Outside AC Unit How to Troubleshoot a Trane Air Conditioner Fan that Does Not Turn On How to Troubleshoot a Central Air Conditioner That Will Not Turn On How to Troubleshoot Your AC UnitLearning Center » A/C & Heating » What To Do When Your HVAC Compressor Won’t Turn OnWhat To Do When Your HVAC Compressor Won’t Turn On

Nest Learning Thermostat: Installation, battery issues, and the importance of the "C" wire My furnace's control board. The "C" terminal has no connection to the thermostat in this picture. (The white wire on the C terminal goes to the A/C.) I connected the unused blue wire (bottom center) to the C terminal. The Nest now confirms the active "C" wire. I recently bought and installed a Nest Learning Thermostat to replace my old non-networked thermostat. I show the installation, demonstrate control from mobile devices, and provide a general review in the above video. It's been about a month since I installed the device, and I found one important issue yesterday. My Nest dropped off the network for 7 hours, and upon investigation I discovered that the battery was low and it turned off the Wi-Fi radio to save power. Many other people have reported problems with the battery, which is scary because your thermostat is one device that you absolutely want to work 24/7 -- you don't want your pipes freezing when you leave town and the Nest decides to run out of juice!

It turns out that my thermostat wiring, like in many homes, does not provide a "C" wire (common 24VAC) for completing a circuit that provides constant power to the unit. This sort of wiring worked great for old-fashioned mercury thermostats -- it provides a red 24VAC power wire, and "call" wires for turning on the fan, heat, and air conditioning. When the thermostat needs to turn on one of those appliances, it simply closes the circuit between the red wire and the relevant call wire. Smart thermostats rely on batteries to power their smartness when no circuit is closed. When an appliance is running (i.e. one of those three circuits is closed), it can perform "power stealing" to sap power from the closed circuit for its operation and recharging the battery. For simple programmable thermostats, power stealing is probably sufficient. However, for a power-hungry device like the Nest that needs to operate a Wi-Fi radio, this mode of operation can be problematic for several reasons: If you live in a nice place like Colorado where you can open the windows and go days without using the heater or air conditioner, the control circuits are never closed and the Nest's battery doesn't have an opportunity to recharge.

Power stealing is an imperfect backwards compatibility hack, and can't necessarily provide enough current to recharge the battery even when the appliances are operating. This is because the current may be limited by resistance in your furnace's control board. When the HVAC appliances are not running and the battery needs to be charged, the Nest performs an even worse hack than power stealing: it pulses the heater call circuit on and off very quickly to steal some power, and hopes that the pulses are short enough to keep the furnace from activating. I haven't noticed any problem with this, but at least one person has found that this wrecks havoc on their heater. The Nest uses a "Power Saving Mode" of Wi-Fi to reduce the power consumption of the radio and prolong the battery life. (And hopefully require less overall power than it can steal from the call circuits.) Nest indicates that some non-conformant wireless access points may not fully support this mode, thus causing the Nest to consume more power.

(Perhaps more quickly than it can be replenished.) I was lucky that my thermostat wiring contained an extra, unused (blue) wire, and my furnace's control board provided a 24VAC common terminal for a "C" wire. After hooking up the blue wire at the furnace and the Nest's base, I now seem to have successfully provided a 24VAC "C" wire to the Nest, and hopefully my battery issues are behind me. I do think that Nest is perhaps overly optimistic about their power stealing and circuit pulsing being able to provide adequate power to the device. There's certainly no warning about this potential issue when you provide your wiring information to their online compatibility tool. Undocumented Nest incompatibility with single-stage wiring - Marco Arment of Instapaper fame reports on his experience with this issue. Options for adding "C" wire to thermostat - Stack Exchange Thermostat signals and wiring - a great resource for understanding thermostat wiring. When Nest needs a common "C" wire - The Nest support page for this topic (which somewhat downplays the severity of the issue).