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So I have power going into junction box into attic 12g/20A.

It fed a light switch, the light switch was chained to microwave outlet. Also in that junction box and connected to the light switch line was the light.

The line to the light switch and the line from light switch to microwave outlet were aluminum. This setup has worked since I bought the house - I did run copper to junction about 3 years ago.

So microwave just doesn't work right all of a sudden a few days ago - it has symptoms of low voltage to the point where clock wasn't even functioning right.

I go up in attic and everything seems clean and tight. [Note voltmeter is at a job and haven't had access to it so I will see what kind of power I am getting tonight hopefully] Grounds are tied to metal box and each other, everything is under the purple AL rated caps.

I gave up troubleshooting so snipped aluminum line in half that ran from light switch to the microwave outlet and directly ran the microwave outlet to the junction box. Boom everything working fine.

Two days later, exact same issue. It almost sounds like something is loose at the outlet but have tried switching outlets and have triple checked all my connections. Is there a chance that the AL wiring is having issues? Any thoughts on what might be the cause? I am going to run a copper line tonight for it but this will bug the crap out of me if I can't actually figure out the cause. Going on 4-5 hours for one outlet definitely record for me.

Addendum: Installed new outlet, hit it with voltmeter and was get 120V - very clean. Microwave worked for 2 days - 20+ times. Boom late last night, stops working. Of course voltmeter at a job again... Is there any reason my lights would work fine but microwave outlet not when they are both branched from same junction power other than a loose connection? Starting to think that the AL wiring is faulty.

  • retighten the screws that connect the AL wires – ratchet freak Jan 6 '15 at 15:57
  • @ratchetfreak - they are combined with the power-in (copper), light switch (AL), and light (copper) and light is working fine. – DMoore Jan 6 '15 at 16:05
  • @ratchetfreak - Also same issue happened before microwave outlet ever touched the junction box (got its power from light switch until I cut it). – DMoore Jan 6 '15 at 16:14
  • Mixing CU and AL is not recommended. There is special anti-oxidation goop you need to keep the corrosion down too. There could be some corrosion happening causing the loss in voltage. I've heard of AL used for main panel runs but not for outlets. If you can replace the AL, I think you will be better off. – scooter133 Jan 9 '15 at 5:43
  • Yes, mixing cu./al. is downright dangerous. FYI, not sure if this is in a kitchen, but circuits feeding the required/minimum dedicated kitchen outlets should not be tied to the lighting circuit. That's code for the kitchen, but good practice in general. – ChiefTwoPencils Jan 13 '15 at 0:26
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Hit this with a voltage meter and everything was fine over time. [More than willing to hear comments on possible troubleshooting.]

The outlet basically worked intermittently. Even when it didn't work I was getting 120v continuously. However while scoping the circuit I found the probably issue. The wiring was ran down a wall and pulled up to the outlet. When it was pulled up it was bent sharply across a nail.

I simply took out that section of the circuit and replaced with copper. (without bending it across the nail)

It was really frustrating but interesting too because 99% of the time this situation is due to a loose connection and funny that a severely kinked cable can cause same issue.

| improve this answer | |
  • A severely kinked cable could cause a loose connection inside the cable. – user253751 May 8 '17 at 7:32

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