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A/C won't shut off

Johnstone Supply has a new "gadget" just for this service nightmare...It's a little breaker, 5 Amp or 3 Amp, that replaces the onboard fuse. No more popping in fuse after fuse trying to track down a short!



  • cal_2
    cal_2 Member Posts: 3
    A/C won't shut off

    Did a seasonal on an A/C today, when I finished, turned stat to the off position, the indoor blower shut down but condenser wouldn't shut off. contacts weren't welded shut, Somehow the unit outside was still getting 24 volts....Any info as to why would help greatly
  • Empire_2
    Empire_2 Member Posts: 2,343
    Break out the meter......

    Since you said the contact are not welded, get your meter and back step from the contactor to the furnace. you have to find out why the 24vac is still there. Could be a short, but could be anything. Your meter will give you the answers. Check the contactor first,....24vac, ok. Go to the furnace term. strip,...24 vac ok,....disconnect the "Y" terminal and see what happens. If unit shuts down, you either have a bad stat,(doubt it) or a short in the stat cable........ Good Luck.

    Mike T.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    Sounds like a classic thermostat problem to me.

    The "Y" terminal on the furnace is simply a convenience terminal and is not connected to anything.

    A short in the low votlage wire going to the outdoor unit will result in an outdoor unit that will NOT work at all, in addition to the frying of your control transformer.

    You have either a defective thermostat or... a poorly wired thermostat. By this I mean....

    Check the wire connections on the thermostat and make certain that the stripped portion of the wire is not overly long. I have seen this happen a thousand times where the "excess" wire would make a connection between the "R" and "Y" terminals on the stat.

    Check it out and let us know how you make out.

    The Professor
  • Empire_2
    Empire_2 Member Posts: 2,343
    Shorted wire...

    What I meant was a short from R to Y which can happen and is also very possible when wire rubbs together or is stripped back carelessly. This should be an easy diagnosis and fix....

    Mike T.
  • cal_2
    cal_2 Member Posts: 3

    thanks for the info..it sounds like an easy fix, but sometimes the easy stuff drives me crazy
  • don_163
    don_163 Member Posts: 67
    Well then

    just wait untill you come across a transformer that blown and, you install a new one and the amp draw looks good.

    Then you get a call three days later and find the transformer or fuse is blown again.

    I could tell you what would be the best fix however,we all must go thru this at least once and our life to fully understand it.So mums the word.

    Crazy can be a good thing sometimes.

  • Kniggit
    Kniggit Member Posts: 123
    y terminal

    Many new furnaces have a seperate cooling, y/yellow speed form the Fan, G/green connection, read the manual before you just walk off.
This discussion has been closed.