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  1. #1
    Join Date
    Dec 2006
    Currently have a Trane XE90 60K BTU. It was installed exactly six years ago, and we've owned the house for two years. The furnace worked fine all last winter and then all fall until just before Thanksgiving, when we had a cold and rainy day. It was blowing cold, so I went into the crawl and found that I had an open high limit switch (4 blinks of the LED),

    Since then, this is what's been done:
    High limit switch replaced.
    Blower speed turned to high.
    Temp rise reduced to 50 degrees (was 58 or so).
    Sensor adjusted.
    The only remaining thing that wasn't fixed was the return static pressure (is that right?) was a little too high--should be .5 and it was more like .75 or .85.
    One guy told me that the return run was too long for its size and that I could shorten it, and that may take care of the problem. I even switched from the quality high-micron filter to a cheaper, more open one to help with that,
    but I could still shorten the run (which I haven't done yet). Should I?

    Well, after all that, it worked fine for two weeks and then the high limit cut it off. Raining that day. Then worked fine for a week (although it's been very warm here and maybe never even kicked on at all). But then it came up again last night (it was humid, but not not crazy or anything). Went into crawl space, pulled the panel off to kill it and restart it, and the burners would kick on for a few seconds and then the high limit would cut it off and run just the blower. So I left the heat off last night, and this AM ran it and it worked great. No high limit problem whatsoever.

    Is it time to throw more money into this unit or just replace it? Will shortening the return run help? Does rain/humidity affect something? That's a theory, albeit a stupid one?

    What I have is an intermittent problem. Never know when it's gonna pop up. I can't rightly say that it's actually too hot and that's why it's tripping. It hasn't rained enough for me to tie it to humidity problems fully, either. Is it the circuit board?


  2. #2
    Join Date
    Mar 2004
    You don't need a new need a new company to diagnose it. Although diagnostics over the internet are not adviseable I think a large majority of us here know exactly what the problem may be...surely a good company and technician on site will know as well.

    Unfortunately, due to site rules we as members can not discuss technical issues with the general public.

    Thank you for your cooperation.

  3. #3
    Join Date
    Dec 2006
    OK, the site rules state that someone may answer my question if they want to. So I hope I didn't break the rules. I couldn't find the prohibition against asking, and "all are welcome," no? Sorry if I did something wrong.

    In full disclosure: I am not a DIY guy. The only thing I would consider DIY is shortening the run, since that merely involves grunt work in the crawl (i.e., I'd use all the existing hardware and re-route it shorter: it's about 20' long now and I could cut it to 12' or less). I understand that HVAC is y'all's livelihood, and I'm not trying to DIY myself out of spending when spending is due--but this particular fix (shortening the run) was quoted to me at a ludicrous xxxx (admittedly a guess on the part of the tech). To me, paying someone to shorten the run, which involves no technical skills but merely a willingness to spend a day in the dirt under the house is not wise stewardship of my meager income.

    I have had two techs out to the house and the second one seemed to be on the ball--he did all the aforementioned tweaks (is that chuckling I detect, folks, as the dumb homeowner thinking my guy was on the ball and y'all have already figured out the problem? ;-)). He never could get the high limit to trip when he was here. Same as the first guy.

    So if I need a circuit board or anything else, I am happy to pay an HVAC tech what is due. I am not looking for pricing or DIY help. I've already paid several hundred dollars and nothing has fixed it. I just want to sleep at night knowing that it is fixed for good. So if someone can grant this Christmas wish, I really appreciate the help.

    Charlotte, NC

    Mr. Garvey,
    Regardless of which part of the hvac field you determine you are capable of performing...sheetmetal or otherwise, there are folks here who have dedicated a good part of their lives into learning what it takes to be the top in their field, to suggest that shortening a duct involves no technical skills is a slap in the face. Slips, drives, pittsburghs, static pressure, velocity,'s not just a walk in the park.
    You came here for sound advice which is what you were given...please use it wisely. And yes, all are wecome here but it is and will remain a forum for professionals in the industry.

    >>> Edit: No Pricing. Please review the site rules before further posting. <<<

    [Edited by Senior Tech on 12-18-2006 at 01:59 PM]

  4. #4
    Join Date
    May 2000
    Indianapolis, IN, USA
    I will say that 4 blinks of the board with no problems with any of the limits in the furnace is one of the many bugs of the original Intell-ignition boards. Had one just today. Replacing to the newest board solves the problem. If your dealer isn't familiar with A-S/Trane furnaces he might want to discuss this with the tech rep at the supplier.

  5. #5
    Join Date
    Dec 2006
    Senior Tech:

    Apologies. I had already read the rules and I was not asking a pricing question. I did not ask if that was fair, or whatever, or even for someone to tell me what is fair.

    Nor did I intend to "slap in the face" anyone here. The tech at my house told me not to pay for him to shorten the run since he said it was too expensive. It is flex tubing, which the tech told me to cut with shears and reroute it directly to the unit instead of going the other direction around pilings. So *I* didn't determine "which part of the hvac field I am capable of performing," the HVAC tech did, your fellow traveller.

    Regardless, all I am asking is for help, so that I don't have to waste any more money for fixes that don't work. If someone here is willing to tell me what I should have done, or there is a preponderance of evidence for one direction I should go?

    Is there a prohibition from me asking for someone in the Charlotte area to PM me to come be the "new company to diagnose it"?

    So if I have offended the folks here, please once again accept my apologies. I am just a human being who wants to keep his family warm.

  6. #6
    Join Date
    Dec 2006
    Thanks, tons, Bald Loonie. Wish one of the two original techs could have been so straightforward and knowledgeable. Would have saved a lot of heartaches over this problem.

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