Is the thermostat the problem? When we have our central air fan set to "on," it runs fine, but when we set it to "auto," the fan does not come on even though the AC compressor kicks in.  (The AC unit is working fine...It comes on and produces cool air). This means that we have to keep the fan on constantly when we want the AC on.  Do we need to replace the thermostat? It didn't seem to have this problem throughout the winter when we had the heat on and the fan set to "auto." Not what you were looking for ? Ultimately, you may have to replace the thermostat. But before you do, try these steps: 1) Thermostat switches make electrical contact across two very small conductors that carry a very low energy signal. This means a low-energy battery, without enough energy to create the required signal, can result in problems like you're experiencing. First step ... purchase a fresh battery and replace the old one. Move the temperature and fan switches to the "Off" position and then return to your preferred settings.

Allow several minutes for the thermostat to "cycle." Then determine if the compressor and fan have come on; 2) Because the thermostat conductors are very small, if the switches are slightly out of position and they will not conduct the required energy to transmit a signal to the fan and compressor. hvac mini split systemTry simply wiggling the switch back and forth gently across the "Auto" position and allow it to stop as you feel it click into the "Auto" position. cost of a new heating and air conditioning unitAllow several minutes for the thermostat to "cycle" and determine if the compressor and fan have come on.cost of inside ac unit These are two easy steps that may allow your system to work. Since you report the thermostat working fine in the "Heat" position, I would expect it to work just as well in the "Cool" position.

I hope one of these simple fixes works! However, if these steps do not work, thermostats are relatively inexpensive and the included instructions make it fairly easy to install. Make certain you purchase a thermostat for the type system you have (ex. heat pumps often take a different thermostat that compressor systems). Then, pay attention as you remove the old thermostat and reinstall the new thermostat following the color codes on the instructions. Finally, if none of these steps work, have a reputable licensed AC contractor service the unit. Most units that are serviced regularly provide efficient service for many years. I have taken these steps many times in the transition between heating and cooling seasons, and I'm always pleased that I didn't turn a small repair into an unnecessary, much larger repair bill. NOTE: This is a great time to change your air filter. Check the size and purchase a replacement while you're at The Home Depot. A Plumbing Associate will be happy to discuss your options.

Relays/capacitors are commonly damaged by power surge ... lightning is a common enemy of this part! The visible indicator is the canister swells like it wants to burst. Relays are beyond most DIYer's desire or ability, so I didn't include it in my earlier list. If you were able to identify the item, a local A/C supply house would likely stock the part and may or may not sell it to you ... some require licensure to sell any of their parts while others will sell non-regulated supplies to anyone. Unless you are particularly handy with electrical, I would save my resources for that reputable, licensed repair shop. You may find the solution another way, but having your annual service and including this repair is likely a good idea. I really like to "Fix It" when I can, but there are times when you just have to let go and call a pro! This may be one of those times. A Quick Warning: "Start Relays/capacitors" build up energy and discharge that energy to help start electric motors.

This discharge can give you a very real shock!!! Be very cautious if you decide to proceed on your own. You are soo welcome, Jennie! When you resolve the problem, take time to come back and explain what you found and how you resolved the problem. I'm certain you'll be adding very useful information to the body of knowledge here on The Community. I have a Carrier Gas Furnace and a Hunter Fan Thermostat 41110. The thermostat will not let me set date or time and/or move button up and down to set temperature. The fan will cut on, so it appears to register to the furnace. It’s a common question we hear from California homeowners in summer, “Why isn’t my air conditioner cooling my home!?”We’ll help you troubleshoot this annoying problem. To do that, we need to ask you a few questions to help pinpoint the cause of the problem.So our first question is…If no air is coming out of your supply vents at all, skip to the second question. If you answered “yes” to this question, follow these steps:1) Check the thermostat fan setting— Does your air conditioner run cold air sometimes but hot air other times?

Make sure the fan setting is set to “auto” not “on”, which will cause your AC to blow air even if it’s not being cooled.2) Check your air filter— If the air coming out of the supply vents is weak and not very cool, check to see if the air filter is dirty and change it if necessary. A dirty air filter blocks airflow to the air handler.  Out of air filters? Here’s our guide on selecting the right home air filter.3) Check the the outside AC unit—Is the outside unit covered in dirt, dust or grass? Is it being smother by a tree branch or bush? Trim them back to give the outside unit breathing room. Is the outside fan not working? A professional needs to fix it. Otherwise the outside unit can’t cool down refrigerant to cool your home’s air.If none of these helped, your AC may be low on refrigerant. However, this is caused by a refrigerant leak, which you’ll need a professional’s help to find and fix.If no air is coming through your supply vents and the AC unit isn’t working at all, follow these steps:1) Check your thermostat temperature— Make sure you’ve set the temperature setting at least 5 degrees below your room temperature.2) Make sure the thermostat is set to “Cool”— Seems simple, but you never know if one of your family members (or the dog) accidentally set it to  “Off” or “Heat” by accident.3) Check the air filter— If an air filter

gets too dirty, it will completely block airflow and freeze the inside unit. Change the air filter if it’s dirty. Here’s our guide on selecting the right home air filter.4) Check that electricity is going to your air conditioner—This means checking service switches that are:If any switches are set to “off”, then there may be a problem with your air conditioner.For example, an AC with a water sensor switch will shut down if it has a clogged condensate drain line and water spills into an overflow pan. Long story short, this means the your AC shut down to prevent water damage to your home.Also, your AC may also be overheating, causing the air conditioner to pull in more electricity than the circuit breaker can handle. So the circuit breaker cuts power to your AC. If the circuit breaker keeps cutting power after your AC runs for awhile, don’t ignore it. It’s trying to tell you something is wrong.Call a professional to figure out why this is happening.If you need help finding any of the switches we mentioned, ask our experts for help.