Saturday, August 17, 2019

The AC is on the fritz

No pictures.

The power feed is supposed to be 240V, AC.

The power feed is actually 120V and the two legs are in phase.

Power out of the circuit breaker is fine and a vigorous 250V +/-1V.

There is a junction box on the outside of the house where the inside wiring is tied to the outside wiring which then runs through a conduit to the actual AC unit. They are connected via a pull-out interrupt.

A betting man would bet that one of the wires pulled out on the AC side of the interrupt and the bare wire end is touching the other side. Had the wire pulled out on the house side, there would have been a Ka-Boom and a tripped circuit breaker.

The only thing stopping me now is a rusty screw that was installed in 1977 that closes out the face-plate on the junction box. I sprayed it with penetrating oil but have little hope of breaking it free.

I am 90% certain that I am going to have to grind the head of the screw off to open up the box. Then, I will have to close it all up with a loose nut-and-bolt. That will be a job for tomorrow morning. Time is our friend when using penetrating oil.


  1. Likely there is a disconnected wire (or perhaps another set of fuses in the disconnect) where one is blown.

    Chances are you are seeing 120 from one phase through the motor windings and back to the contactor? The chances of a perfect short as you describe are kinda slim.

    1. Thank-you sir.

      That is one reason for floating my issues on the internet. I can tap the minds of those smarter than I am.

  2. Not smarter, but it is an area in which I am trained.

    And I have made the mistake before, so....

  3. Does the pull out interrupt have fuses? The one on my AC has slo-blow fuses.

  4. You are more patient without A/C than I.

    My angle grinder comes out very quickly nowadays.

    I keep 2 in service at all times: one with a cutoff disc and one with a flap disc sander.

    I also keep at least one on the shelf in the box for when the $10 (on sale at Harbor Freight) primary one dies.

    I use the heck out of them, me.

    1. ROFL... Right on! I've told customers and students "it's here because it's broken and it may get more broken before it's fixed" And "if you go to the hospital you're getting punctured several times at the least. Might very well get a scar from surgery..."


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