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Bryant Furn. Therm. Switch???

Discussion in 'Uncategorized Threads' started by TC, Dec 7, 2007.

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  1. TC

    TC TS Member

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    Need help, Bryant Series SL/A, Model 125-3940, Ser# 30T55113. Furnace burner is working, fan is not, fan motor checked good.

    Can someone tell me how to test the thermal switch? This is a 3 wire switch to control the blower fan and to shut off the gas valve if upper limit is exceeded.

    Cannot find one locally, not sure of the correct part number but it is marked: Therm-O-Disc, 40015, WA-13, 230. Tony
     
  2. Dr.Longshot

    Dr.Longshot Banned Banned

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    TC take your thermo disc to Johnstone supply if you have one near you, another alternative is W.W. Grainger they may also have one. If you have a/c put the fan swich in on position, blower shoud run. if not you may have a bad circuit board, if it has a circuit board remove it after marking wire locations and look at the back of it with a magnifying glass for a loose solder connection on the relays base.


    Dr.longshot
     
  3. need to shoot more

    need to shoot more Active Member

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    chances are if the furnace is 60s vintage aqua blue and fan control is on the right hand side of the furnace at mid level, chances are slim in finding thes control, 1960s maybe 60% efficent? time for a change out.
     
  4. TC

    TC TS Member

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    Johnstone and Grainger were no help. Is there a way to test the switch?
     
  5. TC

    TC TS Member

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    Sure would like to get this fixed.
     
  6. need to shoot more

    need to shoot more Active Member

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    TC you determined the motor is good that would leave the switch as the culprit, if memory serves me right the switch worked like a reo-stat and basically timed out depending on the amount of restiance, higher restiance ,longer warm up time higher plenium temp before the blower turned on. You could convert this to a three wire fan/limit control but it is a inseration type where you probley have a surface mount warp type switch. I am a firm beliver in repair or replace when it makes sense this is most likely a replacment do to age of system, there are a load of views of this tread with not much feed back???
     
  7. Dr.Longshot

    Dr.Longshot Banned Banned

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    What state are you in? If in Ohio Contact Bryant Habegger for replacement. Their phone number is 614-267-4261 you can order a replacemnt with credit card, they have a store in Columbus and Cincinnati, Ohio.


    Dr.longshot
     
  8. need to shoot more

    need to shoot more Active Member

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    TC, how did you make out on the no heat issue??
     
  9. TC

    TC TS Member

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    Haven't figured out how to check the thermal switch. However, now the situation has changed. The burners won't light. Thermocouple checks good at 24.9mv, Transformer checks good at 29 volts. Don't understand why the burners aren't lighting!!
     
  10. need to shoot more

    need to shoot more Active Member

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    TC, the switch is defective, time to move on!
     
  11. Primedust

    Primedust TS Member

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    T.C

    Go to Johnstone Supply, order a White Rogers 3L03-141 3 wire limit switch.

    Terminal #1 is your hot wire Terminal # 3 goes to the fan and terminal #2 breaks the high limit to the gas valve.

    To test your limit #1 power to #2 fan can be jumped. The fan should run. It is not uncommon for these to fail.

    As for your other problem most furnaces have one or two other auxillary limits. Some are at the top of the furnace and usually there is one or two on or in the blower fan compartment. In most cases these are manual reset switchs. (push button reset). If that doesn't work email me and I will help you over the phone.

    Good luck
    Mark.
     
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