Here is a fun one. I installed 2 LED bulbs into my Genie garage door opener and it caused the microwave to lose power. They are both on the same circuit. When I tested the voltage at the microwave outlet it read 48 volts. That usually means a ground reference problem. Take the bulbs out and the microwave lights up and operates fine. I installed one LED and one incandescent it it works as well.

Any suggestions on a long life bulb preferably LED they doesn’t cause this issue?

  • Hello, and welcome to Stack Exchange. There's no way one device on a properly-wired circuit can make another device see only 48V without throwing the breaker. Something else is wrong; any idea what it could be? – Daniel Griscom Jan 5 '19 at 20:50
  • Have you tested with the Genie LED lights on and off? – BillDOe Jan 5 '19 at 21:18
  • Possibly the LED bulbs are putting a pile of electrical noise on the line, which could potentially both mess up the microwave and the voltmeter reading. – Ken Shirriff Jan 5 '19 at 23:26
  • This circuit powers the garage outlets which is the door opener, a freezer, and since the garage is next to the kitchen it sounds like it was the easiest path to power an installed microwave. The house is 40 years old and I have lived in it for 15. There hasn’t been any issue with power prior to installing the LED bulbs. I know older dimmers and control circuits can behave strangely with LED and CFL bulbs. Maybe the genie uses and older engineered method of control. – Pete Jan 6 '19 at 0:19

No, because you have worse problems than that.

The situation of "LEDs make it fail/act weird, but even one incandescent fixes it" indicates only one thing: a powered switch of some kind, a dimmer, lighted switch, smart switch, motion sensor, something/anything like that.

Obviously, nothing like that should have any relationship whatsoever with your microwave, but the evidence is clear that it does.

And the problem is not as simple as identifying the smart device and changing it to a dumb switch. Something is fundamentally, seriously wrong and dangerous with that circuit, this is just the "canary in the coal mine".

Also beware of multi-wire branch circuits -not that there's anything wrong with them if done right, but they are much more sensitive to being done wrong.

You might also change the breaker to GFCI - it will help motivate you -- I mean will help detect faulty wiring.

  • I still dislike MWBS, but +1 "You might also change the breaker to GFCI - it will help motivate you" – noybman Jan 5 '19 at 22:53
  • There are very few appliances on that circuit and no specialized controls since it’s supplying power to a garage. When I unplug the opener it shows 120 volts to the microwave. The freezer in the garage operates regardless. Also when the opener is connected with LED bulbs installed the power shows 48v hot to neutral and 120v hot to ground at the microwave. Other research (google) talks about reference ground. May be time to replace the opener. – Pete Jan 6 '19 at 0:27
  • My inclination is that it's a anomaly with the garage door opener electronics and not a wiring issue. I will thoroughly test the circuit for my own piece of mind. I think it's in interesting problem and hopefully this thread helps someone else out. – Pete Jan 6 '19 at 18:54
  • @Pete yes, that is definitely the more agreeable outcome. However the facts on the ground do not care what we prefer. A fair amount of head scratching has given me no insight as to what simple thing could cause this. My money is on a miswiring (codevio) interacting with either another miswiring or a simple failure. – Harper - Reinstate Monica Jan 6 '19 at 19:01
  • @Pete, what does the meter show between neutral and ground? Also, do you have any kind of a switch that can be operated from multiple places? – htmlcoderexe Jan 6 '19 at 22:20

Bulbs, especially cheaply-made LEDs can fail internally in various ways. See Understanding and Preventing LED Failure.

However, this particular circuit issue of yours sounds complex, and may be the result o. I would do these things, in this order:

(1) Try completely different, new, premium, LED bulbs from a different manufacturer. (Are the ones you are using cheap, imported, and have you tested each one individually on a separate circuit?)

(2) Test each outlet/receptacle in the circuit using a common electrical outlet tester. You may very well have an outlet that confuses neutral and ground or some other strange combination that is messing this thing up.

Other questions that may need to be asked in order to solve this:

(BTW, what type of instrument are you using currently to test the voltage at the microwave outlet?)

(a) Are there other issues in the wiring of the circuit itself, i.e. things wired in series, or so forth?

(b) Can you use another circuit for the microwave?

(I don't have enough points to make comments yet---so this is entered as an answer!)

  • I am testing the circuit using a digital multi meter. The bulbs I would assume they are cheap versions because they are named for the store that sells them and not GE, Phillips, or Sylvania. I am not sure if that makes much of a difference but worth testing. The problem only happens when the garage door opener is connected and it has only the LED bulbs installed - even if the lights are not illumiated. I do plan on going through each outlet with everything unplugged to be sure it isn't a wiring concern. – Pete Jan 6 '19 at 18:52
  • I would strongly suggest trying a different brand of LEDs... I assume you have tested the LEDs in other fixtures you have and they work fine in those? – yourcomputergenius Jan 7 '19 at 3:55

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