If a ceiling fan capacitor goes bad, you will know it. In more than 80% of cases we see the ceiling fan spinning slow (fan running slow), the culprit is a faulty capacitor. We are going to look into how to tell if a ceiling fan capacitor is bad; you will be looking out for 3 specific symptoms.
In order to fully understand the telltale symptoms of a bad ceiling fan capacitor, we need to have an idea of what is the function of the capacitor in ceiling fans. If you know what the job of the capacitor is, we will quickly see why the symptoms of a bad capacitor arise.
Now, every ceiling fan is powered by a split-phase single-phase AC motor that has two coils:
- Start winding coil. Also referred to as auxiliary winding coil.
- Run winding coil.
The job that the capacitor has to perform is a phase switch between these two coils. Example: When you start the ceiling fan, the start winding coil is turned on. In order for the run winding coil to come online, you need a working capacitor to make the switch.
Technical insight: If we have a bad ceiling fan capacitor, both winding coils (start and run) will be connected in parallel across a single-phase 120V AC supply voltage. When we turn on the ceiling fan, the rush of electric current through winding conductors will produce a pulsating magnetic field instead of a rotating magnetic field (0 to 360°). The pulsating field won’t run or will slowly run the fan; we want a rotating magnetic field to generate torque and propel the fan adequately.
The same goes for switching between fan speeds. If you want to switch fan from Speed 1 to Speed 2, you need a working ceiling fan capacitor.
That means that if you have a bad capacitor, it won’t be able to:
- Make the primary switch from start winding coil to run winding coils.
- Make a switch between Speed 1, Speed 2, Speed 3, Speed 4, and so on.
Based on this understanding, we can now better understand what the symptoms of bad ceiling fan capacitors are:
Symptoms Of A Bad Ceiling Fan Capacitor
If there is something wrong with the capacitor, we will see telltale symptoms just by trying to operate our ceiling fan normally. Here is how to tell if the ceiling fan capacitor is bad:
- Ceiling fan doesn’t even run. When you try to turn it on, it’s basically dead; nothing happens. You usually hear a noise from the fan motor. You will still be able to rotate the fan using your hand. Culprit: Capacitor unable to switch between the start and run coil.
- Ceiling fan spins slowly. Let’s say your new 48-inch fan was spinning at 200 RPM (revolutions per minute) when you first got it. Now it rotates painfully slowly; less than 50 RPM, even if you switch it to the highest fan speed setting.
- Some fan speed settings don’t even run or run the ceiling fan much slower than before. Example: Speed 1 runs normally, Speed 2 doesn’t even move the blades, Speed 3 moves the blades but slower than Speed 1.
In short, if the ceiling fan doesn’t start, spins slowly, or some fan speed settings are rotating the fan slowly or not at all, you have a case of a bad ceiling fan capacitor.
Hopefully, this gives you enough insight to diagnose and detect if you have a bad ceiling fan capacitor.