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Readytoplumb 03-16-2014 01:36 AM

HVAC Troubleshooting Help
 
Hi,

Would some input on this issue I'm having. I have a central HVAC and my thermostat sometimes turns off on its own and the vents only blow warm air, no matter what setting the thermostat is
turned to. Also, - though I suppose it could be unrelated - I think I should add that a few months ago the motor broke down and was replaced.

If anyone has any ideas what's going on, I'd be grateful to hear them.

Thank you!

beenthere 03-16-2014 04:31 AM

If your thermostat is turning off, then you shouldn't have any air blowing out of the registers.

Depending on your outdoor unit. It may have a safety switch in it that is shutting it off to protect the unit.

What have you checked.

Readytoplumb 03-17-2014 03:23 PM

New info on problem
 
This is a tenant's unit, so only now after taking a look at it myself am I getting a better handle on the problem.

Cold air does come out of the register, but after a certain period of time (don't know how long) the cold air stops and I'm told hot air comes in it's place. And the thermostat display no longer shows anything at all.

So, it's not that the compressor doesn't work or that fuse is blown. But something is happening intermittently to cause the A/C to stop functioning.

Could it be I just need to change out the thermostat control module on the wall?

Any help hugely appreciated!!

beenthere 03-17-2014 03:27 PM

Check if its battery operated, and the batteries are getting weak.

Post brand and model number of thermostat and heat pump equipment.

Readytoplumb 03-17-2014 04:15 PM

Tnx for quick reply. Turns out no batteries to replace so I guess it must be hard-wired.

Thermostat Brand: Carrier
Model TSTATCCPB501 #2360015.

HVAC Brand: Carrier
Model: Weathermaker 8000

Any ideas what I should be checking next?
Could it be a logic/mother board issue?

beenthere 03-17-2014 05:04 PM

Check air filter. I believe when that model furnace trips its high limit. It stops putting out 24 volts to the R terminal, which is what powers the thermostat.

Readytoplumb 03-17-2014 05:28 PM

Just checked filter. Installed 9/13 and looks pretty clean. Is it time to dash the DIY dreams?

beenthere 03-17-2014 05:32 PM

Quote:

Originally Posted by Readytoplumb (Post 1323527)
Just checked filter. Installed 9/13 and looks pretty clean. Is it time to dash the DIY dreams?

Not really. However, you made need to be there when it does it.

karenbrown67546 11-26-2014 08:15 AM

Hi guys,

I'm not the greatest expert in troubleshooting, but I spared a couple of days browsing the web for helpful HVAC troubleshooting articles and gathered the best of them in the following blog post of mine...which I'm not allowed to share with you right now, maybe later.

52Caddy 11-26-2014 08:44 AM

Quote:

Originally Posted by beenthere (Post 1323507)
Check air filter. I believe when that model furnace trips its high limit. It stops putting out 24 volts to the R terminal, which is what powers the thermostat.

Yep, when I put one of my commercial BAS controllers on my furnace, I found out it was tripping the high limit and killing the 24VAC up to the controller. It took a bit of investigation, but I figured it out when I noticed the discharge air temp shooting up once it started.

Maybe something is wired different, or wrong, and it's keeping the main fan enabled even if it loses the 24VAC at R? Maybe the board is staying powered and the fan goes into an off delay?

beenthere 11-26-2014 04:49 PM

Some furnaces will kill power to the thermostat, but still run the fan to protect the furnace. carrier has a model that does that.


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