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  1. #1

    To Replace the Board...

    ...or not to replace the board. That is the question.

    I have a Carrier furnace, model 58PAV090-14, installed fall of 2000 (11 1/2 years old) Air conditioner works. Furnace does not. Weather has been cooperative. I've been able to make due for the past week and in a week or two probably won't need the furnace at all for another six months, so I'm in a position to futz around with fixing this.

    The first symptom is the red LED is flashing continuously. It is normally on steady, no flashing. It is not providing any codes, just the rapid flashing. The legend on the door panel states the rapid flashing indicates reversed polarity in the 115V AC. Not sure why this would have changed spontaneously after 11 years. I have checked that the hot line is hot and the neutral is not, checked ground and reversed the leads to the control transformer following recommendations on another forum with no success.

    Yes it's getting input from the thermostat. The thermostat can turn on the air conditioner. Also, if the furnace power is turned on while receiving Heat command from thermostat, the main blower turns on for 90 seconds and then turns off. It does this. Problem is that after the blower turns off, it should begin the ignition sequence. Nothing happens. No power (measured with multimeter) is provided to the inducer motor. And if the inducer motor doesn't turn, nothing else is going to happen. I tried to tap the relays to see if they could be freed up to no avail.

    Physically, the control board (no. 1012-940-J HK42FZ009) appears undamaged. No sign of burned conductors. Fuse is still intact. However, some of the exposed component leads are covered in green dust that looks like copper oxide. Is that indicative of something?

    Thirty years ago I used to work on multi-megawatt induction furnaces as big as my living room. Now I'm staring at this furnace the size of a big suitcase wondering what to do next (or dithering because I know but don't want to cough up the money)

    Is there something else that can be checked or should I just change the board and be done with it?

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,376
    The component leads covered in green dust...offhand I'd be looking for moisture getting on the board somehow. Either a leak in the roof, water coming down the vent stack, or moisture condensing inside the vent stack and finding a way to drip on the board somehow.

    If there's no moisture involved, are these oxidated areas electrical connections, such as where the thermostat wires connect to the board? Could be loose connections have contributed to oxidation (heat).
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #3
    Join Date
    Feb 2010
    Location
    Cal
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    1,596
    Quote Originally Posted by mwpiper View Post
    ... but don't want to cough up the money
    If you cough in the direction of a licensed contractor, you'll have a safe, reliable furnace with a repair warranty. It would already be done and working.

  4. #4
    Control board is located in blower plenum at bottom of unit. Most likely source of water is frozen condenser coil that caused condensation to run all over the floor. This happened a number of times when the unit was new because the original condenser coil leaked refrigerant. No refrigerant leaks since that was replaced. Subsequent freeze ups involved plugged filters. Have established that anything that creates significant amounts of dust can will wipe out the filter in a day. Consequently, haven't had a freeze up for a long time.

    If I coughed in the direction of a contractor, they would probably get both lungs. I recently paid a licensed contractor $ for a $ thermostat. Don't really want to find out what the markup is for a $ control board. A series of unfortunate events, besides the furnace, has bones sticking out on the piggy bank and we still have to go halfway across the country in May to see the last kid graduate and come home to join the ranks of unemployed college graduates. Licensed contractors are great when money is no issue. But sometimes you have to decide if you want to pay to put their kids through school or your own and easy, timely and convenient usually gets sacrificed as a result.
    Last edited by beenthere; 04-11-2012 at 06:09 PM. Reason: prices

  5. #5
    Join Date
    Jan 2004
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    PA
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    68,773
    Prices are not allowed.
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    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Jan 2005
    Location
    Littleton, CO
    Posts
    267
    From the sound of it, the board needs to be replaced. It's possible that the realy for the heat sequence failed inside one of the covers and you can't physically see it. Get a board off the internet that most likely doesn't have a warranty or call a licensed tech to replace and have a warranty.
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  7. #7
    Join Date
    Dec 2010
    Location
    Woodbridge Twp, NJ
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    Not for nothing, but you're talking to a bunch of licensed contractors on this site.
    We paid for our education too, you know. What btuhack was trying to say is that we get paid to make sure it's fixed right and any good contractor would come back and take care of it if it wasn't fixed right. Hence the warranty.

    I'm a father of 3 myself so i know stuff is tight right now and you don't was to spend money where it may not fix the problem. I just think it would be one less thing to worry about if you have a pro fix it.

    Unfortunately this is not a DIY site so if you take it upon yourself to replace the board, then you do it on your own volition.
    Every customer you take for granted today will be someone else's tomorrow.

  8. #8
    Join Date
    Feb 2010
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    Cal
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    Quote Originally Posted by DLZ Dan View Post
    What btuhack was trying to say is....
    Dan, you're gonna make a great mother in law for some lucky young fella one day.

  9. #9
    Join Date
    Nov 2006
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    Southeastern Pa
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    Quote Originally Posted by mwpiper View Post
    Control board is located in blower plenum at bottom of unit. Most likely source of water is frozen condenser coil that caused condensation to run all over the floor. This happened a number of times when the unit was new because the original condenser coil leaked refrigerant. No refrigerant leaks since that was replaced. Subsequent freeze ups involved plugged filters. Have established that anything that creates significant amounts of dust can will wipe out the filter in a day. Consequently, haven't had a freeze up for a long time.

    If I coughed in the direction of a contractor, they would probably get both lungs. I recently paid a licensed contractor $ for a $ thermostat. Don't really want to find out what the markup is for a $ control board. A series of unfortunate events, besides the furnace, has bones sticking out on the piggy bank and we still have to go halfway across the country in May to see the last kid graduate and come home to join the ranks of unemployed college graduates. Licensed contractors are great when money is no issue. But sometimes you have to decide if you want to pay to put their kids through school or your own and easy, timely and convenient usually gets sacrificed as a result.
    While we all have sympathy for you, the rules here prohibit giving DIY advice. With your previous experience you could probably do the repair, BUT, since this is an open forum, this thread would become a part of what is essentially a searchable database that is indexed by search engines. That makes whatever we would yell you, a guy who could do the job safely, a case of actually telling the entire English speaking world, and they may not do it safely.

    And we can't have that.

    And, for the record, I have about five things I would check BEFORE I would buy a board.....
    [Avatar photo from a Florida training accident. Everyone walked away.]
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  10. #10
    Join Date
    Dec 2010
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    Woodbridge Twp, NJ
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    Quote Originally Posted by btuhack View Post
    Dan, you're gonna make a great mother in law for some lucky young fella one day.
    Smart A$$
    Every customer you take for granted today will be someone else's tomorrow.

  11. #11
    Join Date
    Jul 2006
    Location
    Virginia
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    4,878
    Mr repairman my furnace is broke come fix it

  12. #12

    Hmmm?

    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.


    Have a nice day.
    Last edited by beenthere; 09-29-2012 at 07:44 PM. Reason: Non Pro * Member

  13. #13
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    Dec 2005
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    Quote Originally Posted by qawsed View Post
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Tough.

    Next time leave your purse at home.
    Last edited by beenthere; 09-29-2012 at 07:45 PM. Reason: Removed quote of Non Pro * Member
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

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