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Install & Replace

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."

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Posted 2012-03-14T19:49:40+0000  by jennieheeb jennieheeb
 

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. Is thermostat broken?

Posted 2013-10-26T03:10:14+0000  by nettarur

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. Is thermostat broken?

Posted 2013-10-26T03:09:49+0000  by nettarur

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.

Posted 2012-03-22T13:46:45+0000  by Pat_HD_ATL
Thanks for your time!
Posted 2012-03-16T00:27:59+0000  by jennieheeb

That's Right Jennie!

 

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.

Posted 2012-03-15T20:58:48+0000  by Pat_HD_ATL
Thank you for the tips.
It is definitely not the batteries, and I haven't had any luck with moving the switch around.

I read some old posts which have lead me to believe that the indoor fan time delay relay could be the problem since the fan works when set to on and cool, the fan works when set to auto and on when set to heat, but the only time the fan does not work is when the fan is set to auto and cool.

Maybe we shouldn't bother with changing the thermostat then??
Posted 2012-03-15T20:03:51+0000  by jennieheeb

Hello Jennie!

 

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; and

 

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. Try 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. Allow several minutes for the thermostat to "cycle" and determine if the compressor and fan have come on.

 

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.

Posted 2012-03-15T14:18:35+0000  by Pat_HD_ATL
 
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