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Thread: American Standard Freedom 90VS Open High Limit, Slow Blower

  1. #1
    Join Date
    Jan 2017
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    American Standard Freedom 90VS Open High Limit, Slow Blower

    One of our units has a 90's vintage furnace, no problems until now. Induced draft motor starts, Burner fires, blower motor starts but runs slow, looks like 300-400 RPM, then tapers down until about 120 RPM (2x/sec visually) but moving some air. No bearing trouble or anything, just won't run fast, then after a minute or two the steadily blinking light starts to flash 4 times repeatedly (open high limit) and burner stops firing, fan continues to run slowly for several minutes, then light clears, burner comes on again - repeat.

    I took the controller off the motor and all looks fine, even replaced a thermal resistor that commonly fails, still a problem. It seems like it would be the motor, but since it runs faster at first and ramps down I wonder if it is something controlling the motor and am thus hesitant to replace the motor as trial and error. Any ideas?

  2. #2
    Join Date
    Jul 2010
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    Sorry but this is not a DIY site . Best advice we can give you is call a service company. You'll be money ahead paying for a diagnosis instead of guessing and replacing parts.

  3. #3
    Join Date
    Sep 2008
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    Reading your post, it sounds like you're parts changing. This could be very costly, and potentially dangerous, especially when dealing with a natural gas appliance.
    I can't believe anyone would arbitrarily replace a thermistor in a VS control module without testing and diagnosing the failure first. Especially knowing what the cost of a replacement module would be should you cause damage to it.

    If you're a technician, you should be posting in the open tech-to-tech forums, get your post count up to 15 and then apply for pro-forum access. There you will have many knowledgeable technicians willing to offer assistance to an up and coming tech.
    If you're a DIY homeowner, this is not the site for you. The site rules specifically state this.

    Sorry we couldn't help any further.
    Good luck!
    "The only true wisdom is in knowing you know nothing" Socrates

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