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Thread: Any HVAC guys here?

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    Senior Member doug1980's Avatar
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    Default Any HVAC guys here?

    Been having some issues with my A/C. So frustrated with it. Can't seem to figure it out and neither did the tech who came out.
    Alaska to Florida, for how long, who knows...


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    Super Moderator crashdive123's Avatar
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    Maybe H63 or Randyt can help.
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    Quality Control Director Ken's Avatar
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    I have a few HVAC who owe me. I'll gladly pick their brains. What's the thing doing or not doing?
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    Senior Member doug1980's Avatar
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    It started working intermittently when we ran the heat pump then the A/C started doing the same thing. The thermostat clicks on but nothing happens. The outside unit just hums and now the blower won't come on either. All fuses and breakers are good. Thermostat is brand new. I'm thinking it could be the capacitor or the 24 volt relay. It's like the thermostat isn't sending a signal to the unit or something.
    Alaska to Florida, for how long, who knows...

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    Quality Control Director Ken's Avatar
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    Try cleaning the relay contacts. Bypass the thermostat and play with the relay to isolate the problem. Your better off messing with the heat than you are the A/C when you do your testing. A/C compressors aren't always that forgiving.
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    Quality Control Director Ken's Avatar
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    Have you checked your refrigerant levels?
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    Senior Member doug1980's Avatar
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    I'll give it a try the guy who came out looked lost but still charged me $200 and did nothing. What a joke. Level is good.
    Alaska to Florida, for how long, who knows...

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    Quality Control Director Ken's Avatar
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    I know a bit about A/C and oil-fired heating systems, but I've never messed with a heat pump.
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    Senior Member randyt's Avatar
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    could be the start capacitor. If the outside unit is humming then it sounds like the contactor is pulled in although I have cleaned earwigs out of contactor contacts before. There are a few things it could be but without being in front of it with a multi-meter to check it's hard to say.

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    Senior Member hunter63's Avatar
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    Haven't messed with heat pumps much,..... around here aren't too popular.....
    make sure you have power in the disconnect or breaker at unit...

    Sounds like contactor is pulling in, (the click sound ), so it's 'calling for cool" meaning T-stat should be OK... if it is you need both sides to have voltage, thru it, (this is where bugs get in between contacts, both in and out to compressor, and to as randyt says,... the capacitor.

    Check all wires, mice like to chew them off.....
    Might also a have a variable resistant relay in line......possibility.

    Capacitor give the compressor a "kick" and if its bad, it won't start......sometimes you can tell by looking at it will have juice running out or bulged out, sometime not, need a "capacitor checker". Cheap fix.....

    If this is good, check ohms across the compressor windings.....should be about 5-6 ohms from one to another, (three leads), if one is "0" means "open", if one is high 60-60.... shorted winding, or if any leads show continuity from lead to case (compressor case)...shorted....Compressor bad....expensive fix or replace.

    Sounds like you need a new HVAC tech........
    Last edited by hunter63; 04-11-2013 at 02:36 PM. Reason: added stuff
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    You are discribing two seperate problems . If the blower on the indoor unit will not kick on that is a seperate problem . I would agree what others have said about the outside unit . That is the contactor . If it were the capacitor the compressor would just hum and try to start and either trip out on internal overload or pop the breaker . However if it is the capacitor the outdoor fan should be running . However , however the capacitors on many units are shared , meaning one side of the cap for the fan the other side for the compressor so the capacitor could be blown severely .

    Intermittant problems are almost always traced back to solid state components . Assumeing your unit has been built in the last 15 or 20 years it probabley has a solid state controller on the indoor unit . This is the only thing I can think of besides the thermostat that could cause both your indoor unit and your outdoor unit to fail .

    Except ofcourse your indoor blower motor is burned up and your outdoor unit has a seperate problem .

    As one of the other guys suggested , first you have to eliminate your thermostat 100 per cent . If it has been replaced by a lumber company type stat then I would look here first . Heat pumps especially are pickey about what thermostat is used .
    Some stats energize the reversing valve . some stats deenergize the reversing valve .

    If you remove the stat be sure to MARK ANY WIRES so they go back exactly where they were, and make sure your power is off so you don't short out your transformer . You can then use jumpers to bring on your indoor fan , usually red to green to make sure that is the problem with the indoor fan .

    Without a tech present I wouldnt go jumping any other wires since as mentioned you could damage your compressor .
    Last edited by riverjoe; 04-11-2013 at 05:02 PM.

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    Senior Member hunter63's Avatar
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    Tough call unless you run down the sequence of what need to happen first, and test each step.....The old this has to happen so that ..that will happen....and oh yeah BTW there are safeties and limits through out.

    Refrigerant levels usually don't come into play unless there is a low pressure(out of juice) or high pressure limit switch(unit so dirty or fan doesn't, causing it to quit....mostly it should run, just not cool.
    Heat pump reversing valves, normally fail in heat mode.....so a control problem could be a cause.....
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    Quote Originally Posted by doug1980 View Post
    I'll give it a try the guy who came out looked lost but still charged me $200 and did nothing. What a joke. Level is good.

    As an HVAC contractor I have had to through the years , adjust bills since the problem obviously wasn't fixxed .
    The worst are as I stated earlier the solid state controllers which can sometimes work fine and other times fail .
    I would call the contractor and explain to him how the problem persists and you have lost faith in the technician . Sound like he charged you full boat for the service call . He might be able to send a senior tech or come out himself at no or little charge . Try reasoning with him before threatening BBB etc and you might be surprised .

  14. #14
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    If the outdoor condensing unit is humming, it is either a bad start / run capacitor, or the compressor is locked up. In either case that normally blows the fuses in the disconnect switch feeding the unit unless someone has installed oversized fuses. Another thing that could make the compressor just hum is the loss of one phase. You should have 2 120 volt circuits feeding the compressor, and the loss of 1 phase will not allow the compressor to start but it may just sit there and hum without blowing the fuses. A bad contact in your main contactor may be the problem. You will hear the contactor close, but if one of the contacts has failed, the compressor will not start. There is also a bi-metallic overload on the compressor called a Klixon switch, check that as well because they do go bad. It opens when and if your compressor overheats which opens one or both phases of the compressor power circuit.
    It definateld sounds like a contactor, capacitor, or Klixon switch malfunction to me!

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    Senior Member doug1980's Avatar
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    Got a new tech coming out today for no charge on the diagnosis. Hope we get it solved. Sometimes it works fine but other times it won't kick on. Who knows.
    Alaska to Florida, for how long, who knows...

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    Senior Member doug1980's Avatar
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    No tech yet but it's magically working again. Bet when it reaches the temp setting and shuts off it won't come back on though.
    Alaska to Florida, for how long, who knows...

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    Administrator Rick's Avatar
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    Why am I guessing a pair of tiny little hands are playing with the thermostat?
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    Super Moderator crashdive123's Avatar
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    Quote Originally Posted by Rick View Post
    Why am I guessing a pair of tiny little hands are playing with the thermostat?
    How about that. You are one observant fella to notice that Doug had really small hands.
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    Senior Member doug1980's Avatar
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    Lol not that simple. Circuit boards are bad. Well going bad. Gotta wait for the parts to come in.
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    Nevermind .
    Last edited by riverjoe; 04-15-2013 at 02:19 PM.

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