While we were cleaning out a friend's garage I turned on a heater fan. I didn't take a good look at it but it has a digital display, thermostat, and I'm pretty sure it's a wire element type. It started getting dark while we were cleaning and my friend was moving something around and told me to turn off the heater so that the light would get brighter. I turned it off and the fluorescent light in the ceiling got way brighter and stopped flickering.

I haven't had a chance to look at the breaker box yet, but from what she describes to me, it sounds pretty bad. She says that if you turn too much stuff on in the house, the breaker trips. I'm assuming that the whole house is only on a few circuit breakers.

My question is, why would the heater fan cause the fluorescent light to flicker and dim, and can I expect this same behavior from incandescent or LED bulbs (non-dimmable)? Is this indicative of improper wiring in the house, or just too much going through a single breaker, or is it maybe something with the (probably) shaded-pole fan inside the heater causing noise in the grid?

2 Answers 2


This is indicative of overloaded circuits and/or improper wiring. Check the voltage at an outlet both with and without load. Recommended range for a nominal-120 VAC line is 110-124 VAC for Range A.

If the voltage drops below that, or if circuit breakers trip frequently, remove loads (especially a heater, which can draw 15 A) or rewire the house. Some older houses had aluminum wiring, which makes poor contact at connections with age. Don't risk a fire caused by overheating circuits.

  • I'll bring along the multimeter next time I'm there and test the outlet. Rewiring the house isn't possible, but I'll look and see if I can tell if it's aluminum wire. Dec 26, 2016 at 10:13
  • I hate to post to this after it's been so long, but I've had ample time now to look at the wiring for the house and the garage in the last month. It's not aluminum wiring, it's actually fairly thick copper, but the wiring in the garage looks like it was all an after-thought. It's all controlled by a 3-way switch, one in the house and the other in the garage. From the switch it goes to an external light, an unused fixture inside, another fixture in a separate room, an outlet, then another outlet, all in series. The flourescent light was at the last outlet. Feb 2, 2017 at 4:41
  • I've since added a new switch that controls a light fixture with an LED bulb in, and a new outlet in parallel with the main switch. The only thing now is that there are very few outlets in the garage, so we're putting a lot of power through just one or two outlets and using power strips. Also the garage isn't grounded, at all. I'm slowly working on fixing it up, but the homeowner doesn't want me to mess too much with stuff,even though her house is a standing fire hazard Feb 2, 2017 at 4:44

It is not possible that there is to much current used, then the circuit breaker would break the circuit. It's verry unlikely that there is too litle voltage, unless the circuit is connected in series and the switch changed that to parralel (verry unlikely though)

My gues would be that there is something wrong with the starter of the fluorescent light, it looks a bit like this:

fluorescent light starter

You can try to replace it, it might solve some problems.

Also take a look at the breaker box, maybe they did something weird with the wiring.

  • With the breaker tripping the circuit may be over loaded and causing a brown out condition. Some ballasts are sensitive to low voltage conditions and power factor shifts.
    – Ed Beal
    Dec 22, 2016 at 14:21

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