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Thermostat unit not cooling house.

I just bought a new house, and I cannot set my honeywell thermostat. If I try to make the house cooler and press the down temp arrow, it will display that the "set" temp is changing, but the unit doesn't turn on, and the current room temp doesn't change. We have the thermostat set to cool and the fan is on. Any suggestions?

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  • melaniedash May 09, 2009

    The heat has been run successfully, but not the cooling. I'm not sure about the outside unit, I'll have to check.

  • melaniedash May 09, 2009

    I checked the outside unit, and it doesn't appear to be coming on.

  • melaniedash May 10, 2009

    All breakers are turned on. I turned off the AC breaker momentarily and back on - no effect.

  • melaniedash May 10, 2009

    Yes, there is. There are two red lights inside, and neither is lit.

  • melaniedash May 10, 2009

    Inside the box there is a fuse, with two red lights. They both read Line 1, Line 2 - Fuse bad when lit. There is an "ON" - on the top, and an upside-down "OFF" on the bottom.

  • melaniedash May 10, 2009

    we set the thermostat to cool and the temp to 40 (as low as it would go) and waited approx. 30 sec. There was no clicking in that time. We tried switching it to off, then back to cool, but no results.

  • melaniedash May 10, 2009

    When the thermostat is switched to cool, the display momentarily changes to the temp that it is set at in "cool" mode, and it will turn on the fan, but no AC. The fan turns on almost immediately after setting it to cool.

  • melaniedash May 10, 2009

    Thank you scspriggs! You have really helped out. At least I won't feel so clueless when I call for service tomorrow. I really appreciate you taking the time to help out.

  • Samuel Charles Spriggs May 11, 2010

    This is not what I was hoping.

    Is there any indication you get from/on the thermostat that it is going into cool mode? -- Such as a click at the thermostat or some display changing? If so how long does this take after you set tstat to cool.

    I'd start by turning the tstat to "off" for a few minutes.

  • Samuel Charles Spriggs May 11, 2010

    Okay. It sounds like all the proper power is connected to the A/C unit.

    Next two prime suspects to me would be the A/C compressor relay and the compressor run capacitor.

    First, to investigate a bit on the relay:

    - you will need someone inside operating the thermostat

    - someone outside to listen for a clilck

    - set the thermostat to cool and set the temp very low

    - when the thermostat powers the controller (which may not be immediate) the relay outside is energized -- good or bad, the relay usually clicks when it's energized

    -- if you get clicking, that tells us the controller/tstat is probably okay

    So, run this test and let me know what you find.

  • Samuel Charles Spriggs May 11, 2010

    Sorry, I should have asked as well, if there is a handle on this outside box, or maybe one or two toggle switches in the front cover?

  • Samuel Charles Spriggs May 11, 2010

    That sounds like a promising clue, but nothing definite yet.

    Can you open the outside box and tell me how it is labeled and what any text reads if there is any?

  • Samuel Charles Spriggs May 11, 2010

    There should be a fuse box or a disconnect box outside on the wall near the A/C unit -- is there?

  • Samuel Charles Spriggs May 11, 2010

    I would check the A/C breaker in the main service panel. It's a 220 breaker (double pole), i.e., it has two "switches" on it. This may have been turnd off for the season.

    If this is not the problem, let me know. We'll go to the next step.

  • Dennis Boxerman May 11, 2010

    even though you are changing the "Set" temp., is the outside unit coming on?

    Let me know and we can continue.

  • Samuel Charles Spriggs May 11, 2010

    Have you successfully run this A/C system since you moved into you new home?

  • Anonymous Mar 13, 2014

    Ritetemp thermostat. Don't know how to operate it yet?



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Okay. Here's what I suspect in order of probability:

- low refrigerant charge
- contactor not getting 24 volts from controller (controller problem)
- bad contactor
- bad capcitor

I'd start with the charge, as suggested by mastatech. But if it is low, you'll need a service call, anyway, so pressing the needle valve may not be necessary.

I'm assuming you're not going to be taking the unit apart and testing stuff, so you'd need a service call for that as well.

I guess bottom line is, call for service. At least, I think we've ruled out simple stuff which will avoid paying for a service tech to come out and flip a switch.

Maybe mastatech has some other recommendations.

Posted on May 10, 2009

  • Samuel Charles Spriggs May 10, 2009

    You are very welcome.

    If you wouldn't mind, could you tell me what the service tech finds/does?




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Check the outdoor unit it could just be turned off at the circuit breaker if it is runninng outside and the air out of the top is cool. Either the compressor is not running or there is no charged. just press in the needle valve to see if it has a charge.

Posted on May 10, 2009


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