Aux heat is running when stat is set at 75, why?


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Old 10-07-08, 07:10 PM
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Aux heat is running when stat is set at 75, why?

Walked into my home and the aux heat was running. The stat was set at 75 so there is no reason the heat should be on. I have an older AC unit, and not sure if this has anything to do with it. Can anyone tell me why this would happen? What would be my first step to fix this problem? Any suggestions would be gratefully appreciated, since I live in Florida and its HOT!

We tried to replace the old stat with a new one hoping this was the problem but still didn't solve anything.

Help.
 
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Old 10-07-08, 07:35 PM
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Assuming you have electric resistance heat, there could be any number of problems. The best thing to do is to locate the 2 pole circuit breaker in the breaker box for the heat and turn it off. This should leave you with the 120v for the blower and hence, the AC will still work. Then call for service.
There could be control circuit shorts, sequencer problems, relay points welded...
 
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Old 10-07-08, 07:55 PM
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didn't work

There are double breaker for the heat and double breaker for the AC. Turned off the heat breakers and the AC won't run. We turn the heat breakers back on and the AC runs, but so does the aux heat.

Another question I have an older Carrier AC unit FA4ANF030, and looking for a replacement thermostat. The AC has a heat pump with aux heat obviously, and we also think maybe we have the wrong stat. What a nightmare. Trying to save some money.

Thank you
 
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Old 10-07-08, 09:15 PM
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Is the t-stat a new one or old one?

Aux shouldn't be on display in cool mode..

What is the make and model of the t-stat?
 
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Old 10-08-08, 02:57 AM
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The original thermostat was an old one. It was a Bryant Mercury. We picked up new one a Lowes a Honeywell rth6300B, and the wires just don't match.

The wires in the wall are
x
g
w2
o
y
r

and the the new thermostat shows

x
g
w or w1, h, o, b
y or y1, m
r or rh, 4 v
rc or r

So the issue is where does W2, O, and Y go? Do you combine W2 and O and place in one slot, or do you combine O and Y and place in one slot? Or which one is not needed.

I told ya what a nightmare.
 
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Old 10-08-08, 05:48 AM
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I am afraid you'll have to take that t-stat back, and get the right one.

Right t-stat you'll want is the RTH7400.

What was the model # on your old Byrant t-stat?
 
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Old 10-08-08, 08:15 PM
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Okay so now we found out the thermostat is a White Rogersís extremely old one. We called White Rogers and they had a replacement. We picked it up, we installed the thermostat, but now the ac won't stop running. It shows the inside temp is 83, and the ac is running and temp won't go down, and it won't stop either. Now what could be wrong? Will I damage the ac unit if I run it all night like that? Help

Thank you
 
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Old 10-08-08, 08:23 PM
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No more Heat

I did not have time to read the whole thread but if the thermostat is not calling for heat and the stat is working and electric heat is on it usually leads us to a bad relay in the heat kit this happens all the time as these controls live all summer in a cool wet environment due to improper insulation and airflow, combine that with a filter that does not get changed when it should and you have a 53 degree 80% humidity bi metal plate. You can see why they fail. Pull the fuses out of the heat kit so you will have cooling and either call for service or use a meter to figure out which relay is not working.
 
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Old 10-08-08, 08:29 PM
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Originally Posted by mellie0718
Okay so now we found out the thermostat is a White Rogersís extremely old one. We called White Rogers and they had a replacement. We picked it up, we installed the thermostat
Are all the wires/letter matching from the old one?

but now the ac won't stop running. It shows the inside temp is 83, and the ac is running and temp won't go down, and it won't stop either.
Is the blower running inside/air blowing out of the vents? Outdoor unit running?

Will I damage the ac unit if I run it all night like that?
You can damage it if the blower inside is not running.
 
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Old 10-08-08, 08:32 PM
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The auxillary heat went away, but now it won't cool off, or shut off. If I run it for the night, will I damage the unit? I should be able to get the services guy out tomorrow. I hope.
 
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Old 10-09-08, 08:03 PM
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Did you get a tech out today for your system?
 
 

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