Original to the house so like 16 years old. Simple Honeywell with heat, cool, em heat, and off. Fan on off and auto.
I have the A/C set to 72* but stays cooler at 64* Its 90* outside it it should not be colder than 72*
Anything to look for before just swapping in a new thermostat?

This message has been edited. Last edited by: Black92LX,

You could just pick up an inexpensive standard t-stat to replace it and test...

That's a 26° differential, is it running continuously?

Simple Honeywell non-programmable

Honeywell TH3110D1008 or sim

They used (2018) to be about $30

JB

I've got a first gen Nest and love it.

I like the simple programmables. You can set it so it gets warmer/colder at times no one is at home, and cools/heats more when you want that. Most allow you to have varying settings for different days of the week.

The smart one like the Nest learn that on their own, but how hard is setting one?

quote:

Originally posted by mcrimm:
I've got a first gen Nest and love it.

I will only use Nest now - I've got 3 set up! One of the first things when we moved in was replacing the old thermostats. One on each end of the house and another for the boiler/radiant floor heating.

I don't use the learning feature, but use the heck out of the schedules and the ability to pull up and adjust from anywhere on my phone.

quote:

Originally posted by jhe888:
The smart one like the Nest learn that on their own, but how hard is setting one?

Setup is exceedingly easy - pretty much the same as any other thermostat. Then it's just a matter of which features you want to use, which is done from the app on your phone.

Thermostats seemed to be one of those things that lasted forever for decades.
Recently I've had to replace 3 in my shop and one at home.
Unfortunately they are another thing that's only made in that country we shouldn't buy things from because they are mostly crap now.

I love home automation, and gadgets in general, but, for a thermostat, I never saw the sense in making things more complicated than they had to be.

I installed a Honeywell RTH7600 programmable t'stat probably ten to fifteen years ago and never regretted it. It continues to serve our needs nicely.

The RTH7600 is no longer made. It seems the Honeywell RTH7560E is the model that succeeds it.

If our t'stat died, that's what I'd buy.

$80 at Home Depot or Lowe's, and probably in stock. $60 at Amazon. HD and Lowe's will probably price-match.

Sounds like the contact is stuck. If mechanical, you can run high/ low a few times to try and free it up, otherwise just get a replacement.

Even basic programmable heating/ cooling digital thermostats are under 25 bucks now.

I've still got some apartments with thermostats that have mercury in a glass vial, set on a thermal spring.

They may not match the degrees to the scale on the cover, but by golly, they work seemingly forever.

So it is just running constantly.
Even completely shutting the thermostat off the unit was still running.
It is the downstairs unit so I shut the unit off at the switch on the unit itself.

quote:

Originally posted by ensigmatic:
I installed a Honeywell RTH7600 programmable t'stat probably ten to fifteen years ago and never regretted it. It continues to serve our needs nicely....If our t'stat died, that's what I'd buy.

That's exactly my story too. I really like it and it isn't much more complicated than the super simple ones.

I have the thermostat that came with my new HVAC if you want it. It's programmable but I went with a Nest.

I had a 15 year old model of the Honeywell everyone is talking about about.

I switched it to the Honeywell T9 when we remodeled.

I like being able to see it and control it on my phone. It also come with a room sensor that can go in any room that acts like a secondary thermostat.

We also have a older model of the RTH9585WF1004 has all the same features without the room sensors and with more colors and has the same form factor as the original.It is also wifi. But it has a different Honeywell app.

No problem with either. put them in 2019

quote:

Even completely shutting the thermostat off the unit was still running.

If you can't turn it off with the switch on the thermostat, you may have a loose wire touching something that it shouldn't.

quote:

Originally posted by Some Shot:

quote:

Even completely shutting the thermostat off the unit was still running.

If you can't turn it off with the switch on the thermostat, you may have a loose wire touching something that it shouldn't.

This is what I was thinking.

Check your compressor contactor on your condenser, sometimes they will weld themselves closed when they are worn out.

quote:

Originally posted by Some Shot:

quote:

Even completely shutting the thermostat off the unit was still running.

If you can't turn it off with the switch on the thermostat, you may have a loose wire touching something that it shouldn't.

quote:

Originally posted by Airpusher:
Check your compressor contactor on your condenser, sometimes they will weld themselves closed when they are worn out.

I am far from HVAC inclined.
Suggestions as to where and what I am looking for?

quote:

Originally posted by Airpusher:
Check your compressor contactor on your condenser, sometimes they will weld themselves closed when they are worn out.

I could be wrong, but depending on your setup, I don't believe that will turn the air handler on. Now a loose wire crossed up IN the thermostat, or the thermostat itself, MIGHT cause this.

Also, I'd be curious how the changeover valve (reversing valve) is setup. Normally it has a separate wire to turn it on for cooling, unless you have a Rudd, Rheem or other brand where it is off during cooling. Otherwise a single stage will use the O wire for changeover and turn on the compressor(Y), then the blower(G)... That's typically 3 wires, or perhaps just 2 for Ruud/Rheem, that have to be on to get cooling AND the fan blowing. Is this an AC unit, or a split system/heat pump/furnace?

I'd look for a short inside the t-stat, or simply change it.