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More circuit board problems!

OK Fellas, I've got a headache!
I have a 1 year old Warm Air Furnace that has gone through 4 circuit boards in approx. 8 months. The wiring seems OK and it has a T87F 2873 Thermostat which is OK as well.
There doesn't seem to be any voltage problems.
All the connections have been checked and re-checked.
Any ideas??? I'm desperate with this one.



  • Bill NTSG
    Bill NTSG Member Posts: 321
    what about

    Do you have a good ground? Is the polarity right? How about the ambient temperature. Is this gas or oil? Atmospheric or forced draft? Gotta' be something going on there.
  • Steve Ebels
    Steve Ebels Member Posts: 904

    What kind of furnace? model #? Who installed it? Any other electrical problems noted in the house during the same time period?
  • chuck shaw
    chuck shaw Member Posts: 584
    Electrical Problems??

    I went on a service call, homeowner was at the end of their rope. They had had 6 no heat problems since mid September. Gone through a series of primary controls and transformers. I started asking questions, and found out they had flickering lights, and a few other problems. I started looking around, was only getting about 95VAC at the burner. Traced it back, found the same at the circuit breaker. I checked accross the leads comming in from the street, found 17VAC, instead of the expected 220VAC. Called in an electrician. Seems a tree branch was rubbing the neuteral wire comming in from the street. Screwed up the voltage, and was most likley the cause of the problems. Seems on the colder windy nights, the burner would die out. Guess when the tree branch was rubbing the neuteral the most. Called the electric utility, and seems to be all set. Sometimes, you just got to look a little futher.

    Chuck Shaw

    To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Sorry, don't know

    Sorry, but I don't have the Furnace name, model number, etc
    at my disposal at this time.
    Actually, this ia a job one of my co-workers is trying to repair once and for all if possible.
    I'll get the info on Thursday. I know I'm going to end up with this job for sure!

  • Jim_13
    Jim_13 Member Posts: 18
    Manufacturer's thoughts.

    Whoever made a furnace that has a board failing every other month will want to hear about this. Contact the manufacturer at once. They may have a tech bulletin out on this board for a heating cooling furnace application. Doing this may will save the rest of your hair that hasn't yet been pulled out. At the very least they will have a plethora of suggestions that they want you to check and report back to them. Rapid board failure such as this is very bad for Brand recognition.
  • John G. Merritt
    John G. Merritt Member Posts: 140

    Jim, I think you are 100% right. Never gave it a thought.
    No excuses, just never gave it a thought.


  • John G. Merritt
    John G. Merritt Member Posts: 140
    It is a Carrier Furnace

    Just found out by phone this is the newest oil fired Carrier Furnace. My co-worker thinks the model # is CLA120.
    He also claims that High speed and low speed terminals for the blower were jumped out. That was changed.
    Hope this board holds up.

  • EricR_2
    EricR_2 Member Posts: 43
    Were a Carrier dealer

    but all of our business is gas fired forced air. I'm sure if you post the model and serial number I could get you any tech bullitens or other necessary info and e-mail it to you or maybe John Williams can help you out. Let me know.

  • Jack_23
    Jack_23 Member Posts: 153

    I once had problems with htg equip in my house when we first moved in. Couldn't keep light bulbs and alo lost a good VCR that winter. Heat off frequently throughout winter. Drove me nuts. Found the neutral was totally corroded at the elec meter. New service and n more issues whatsoever. Grounding and clean power are critical to happiness of todays components. My experience is it is rarely a "problem" board. Especially after repeated attempts to repair and replace. Almost always poor ground.
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Wrong model number on carrier

    Sorry guys,

    The correct model number of this newer Carrier furnace is 58 CLA. Circuit board number is ST9003.
    Oil Fired unit. T-87 T'stat.
    High speed and low were jumped out.
    No other electrical problems in home.
    Any more ideas?
  • Mason
    Mason Member Posts: 102

    John for starters, call your local Carrier Dist. I am curious about the number on that board. I thought it should have been an ST9103 not a 9003 (not being picky these things are important). I have several of these units out there (unfortunatley all high boys) Anyhow the 58CLA is a low boy 120k. The board controls the fan on time not temp so check your amp draw at start up and after a little run time to get things heated up. Also check your blower wiring as I have seen them chafe inside of a greenfield when run from fron to back to get to the blower. Is there any service history other than this board?? What is the cause of the board failure?? Is it the same failure over and over? Where are you getting these boards, are they not asking what you are doing with so many of them?? Have you filed a warranty claim??
    EDDIE GRIERSON_2 Member Posts: 32
    board failure

    Due you have a megaohmeter? If you due. Pull all the wires from the board and meg them out to ground. Also meg the motors and wires to each other. GOOD LUCK
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Same failure it seems.

    Mason, Same board failure over and over, and there is no other problem history. I'm the fourth Tech on this.
    The fan side fails every time.
    It is a ST 9003.

  • Jack_15
    Jack_15 Member Posts: 12

    Two things, i have never had a problem circut board, & i have never jumped out hi & low speed. Since i have never done that i do not know what would happen when you do. When different speeds are required for heat & ac there is a isolating switch or fan center separating the two.

    Hope this helps,from Jack
  • Duncan
    Duncan Member Posts: 43
    Board failures

    Generally speaking, most motor control board failures I see are the onboard relays gettin' smoked. Can't speak to that exact unit you're talking about.

    Different motor speeds jumped out... not sure exactly what that means, but if there is a short and an overcurrent condition, the weakest link will go first. A tiny relay could be a likely candidate. If you fixed the jumpered problem, and IF the motor's OK, you may have gotten it.

    I'd definitely measure the blower motor current draw, make sure it's OK, and have a talk with a manufacturer's rep.

    You could test one of the old boards if you still have one... If the coil side sees the right voltage, but the contact side doesn't switch the voltage, there ya go. Look for burned spots on the board for clues.
  • Dale
    Dale Member Posts: 1,317
    New Carrier circuit boards

    If this is a New design they seem to be field tested on the customer, they fix what they find to fail. After a year or so the problems usually go away. The jumpering bothers me, all motors back feed voltage off the unused motor windings, sometimes alot more than 120Volts. Most modern circuit boards have dummy spades or screws to store unused motor leads so the backfeed won't hurt anything. The other thing, I agree with the other posts that the fan relay on the boards is usually the first thing to fail, I would amp the motor on start and during run and compare it with another furnace that doesn't fail. Strange as it may seem too much air flow brings high amps. I would also change the capacitor, I assume this is a PSC motor, starting amps can go up with a leaky capacitor.
  • John G. Merritt
    John G. Merritt Member Posts: 140
    Circuit board problem unsolved


    My Service Manager and Carrier will work on this problem as of 12-27-02.
    I am out of the picture for now. When resolved I will find out what the problem was and post it.
    Don't have much hair left.

  • Leo
    Leo Member Posts: 767
    Service Manager the Great

    Now John after going nuts you get taken out of the picture and the "Service Manager" takes over. He should have the rep working with you and he should stay behind his desk where he is less dangerous. Better yet he should go out and get the coffee while you and the rep go to the job site.
    Good Luck, I have watched this with interest.

  • John G. Merritt
    John G. Merritt Member Posts: 140
    Service Manager the Great

    Hey Leo,

    I agree, but have no say. Typical of big Oil.

  • Leo
    Leo Member Posts: 767
    Gee, Now it gets even better


    Now that you say it is Big Oil I can see it coming. The manager is joined by two more suits, the rep is razzel dazzeled and gives up all his freebies in hopes of getting or keeping "Big Oil's" account only to find that decision is made by bean counters who go with the lowest bid. Who then tell you all the reasons why they aren't the low bid on the jobs you go out and do.
    Been there, done that, say the suits got the tee shirts to prove it,

  • John G. Merritt
    John G. Merritt Member Posts: 140
    That's it Leo!


    You've got it. 100% correct.
    I will probably end up back at that job anyway. I think.
    Will let you know the final results when I do. Meanwhile I'll go with the flow. There is some humor in all of this, as I watch the SM make an **** out of himself. And he will!
    Always does.

  • John G. Merritt
    John G. Merritt Member Posts: 140
    Circuit board problem resolved????


    The verdict on the Carrier/Circuit board problem
    seems to be that the high speed and low speed on the fan side can't, or should not be jumped out!
    That was already corrected. Now it seems, nothing is wrong!

    Stay tuned.

This discussion has been closed.


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