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    herbison8's Avatar
    herbison8 Posts: 5, Reputation: 1
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    #1

    Jan 22, 2009, 10:24 PM
    Replaced Fan Limit Switch, but fan still won't stop!
    Hi everyone, Im new here. Well I have a 1987 Olsen Forced air furnace. I've been in this house now for about 4 months. I realized one day that the furnace fan didn't shut off. I did some searching and decided it must be a faulty fan limit switch. I got the correct Honeywell replacement limit switch, shut off the power, installed it, and as soon as I turned the power back on the fan started instantly. It just won't shut off, I don't know what else to do. Any suggestions/help would be greatly appreciated.. Thanks!
    MarkwithaK's Avatar
    MarkwithaK Posts: 955, Reputation: 107
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    #2

    Jan 22, 2009, 10:27 PM

    Did you put the switch to AUTO on the fan cycle/limit?
    Missouri Bound's Avatar
    Missouri Bound Posts: 1,532, Reputation: 94
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    #3

    Jan 22, 2009, 10:27 PM
    Have you checked your thermostat fan control? There is an ON or AUTO position on some thermostats, if it's set to ON the fan runs continuously.
    herbison8's Avatar
    herbison8 Posts: 5, Reputation: 1
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    #4

    Jan 22, 2009, 10:31 PM

    Limit switch is pulled out into the auto position.
    The thermostat fan control is set to auto as well.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #5

    Jan 22, 2009, 11:12 PM

    Come on guys. The most common reason why the blower keeps running is a defective blower relay assuming the simplest of blower controls. The blower relay contacts are most likely fused.
    MarkwithaK's Avatar
    MarkwithaK Posts: 955, Reputation: 107
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    #6

    Jan 22, 2009, 11:34 PM
    Quote Originally Posted by KeepItSimpleStupid View Post
    Come on guys. The most common reason why the blower keeps running is a defective blower relay assuming the simplest of blower controls. The blower relay contacts are most likely fused.
    Not with this type of control. With newer systems that have circuit boards, yes this could be an issue but with a combination Fan/Limit switch there is no relay to stick.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #7

    Jan 22, 2009, 11:41 PM

    It happened with an old Armstrong I worked on. Fan center and limit control. Fan relay stuck. The limit control had the summer/winter mode too.

    I don't know anything about an Olsen furnace.
    herbison8's Avatar
    herbison8 Posts: 5, Reputation: 1
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    #8

    Jan 23, 2009, 12:17 AM
    Ok so how do I know if I have a blower relay? If so what do you mean by fused?
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #9

    Jan 23, 2009, 04:50 AM
    Post a few pics of the unit if you can. Does the system have air conditioning? As KISS said, fused means stuck together, like a spot weld.
    herbison8's Avatar
    herbison8 Posts: 5, Reputation: 1
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    #10

    Jan 23, 2009, 11:17 AM

    Yes it has Air Conditioning, and I do remember hearing a lot of clicking when the fan used to turn on and off (functioning properly). Like when a relay makes that clicking noise, except it wasn't just one click it was a whole bunch, sometimes more than other times. Maybe there is a relay somewhere. Ill post pics as soon as I can
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #11

    Jan 23, 2009, 11:22 AM

    Do you have anything that looks like this?

    http://www.white-rodgers.com/wrdhom/...Cat_pg_106.pdf
    Missouri Bound's Avatar
    Missouri Bound Posts: 1,532, Reputation: 94
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    #12

    Jan 23, 2009, 06:31 PM
    The fan limit switch is a heating control. If the unit has air conditioning then there is a blower relay somewhere as well.
    herbison8's Avatar
    herbison8 Posts: 5, Reputation: 1
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    #13

    Jan 28, 2009, 12:41 PM
    Got it fixed! I messed with the limit switch settings a little bit and Viola! She's working. Thanks a lot for the help guys!
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