5v Fan on 3v line

I have a Pi4 that came with a noisy 5v fan.

If I connect the fan to the 3v line it spns slower and is much less noisy.

Is this ok or will it damage the Pi

Ok - thanks

You can just use a series resistor to slow the fan while still powering it from 5V. Exp0eriment with the value of resistor until you get the right speed.

Doesn't seem to be an issue, I've been running dozens of 3B's, 3B+'s and

I've not used fans on the original B, 2B's Zero's or Zero 2's. The only Pi's I've had fail have been a Zero and a 4B which had a passive heatsinks and probably ran too hot for too long, so 3.3V fans can't be implicated in either of those, and could have even saved them.

---druck

That's a much better option than stressing the voltage regulator on the Pi. A 2V zener diode could also be used in series to avoid needing to experiment with the resistor value if 3v is considered roughly optimal. Or 2-3 normal silicon diodes in series.

you shouldn't use grease on small electric motors. Light sewing machine oil is best.

Indeed. without knowing more about what it draws, 'is likely' is just pissing in the wind.

Result!

I too would recommend any of those solutions.

Running a fan from the 3.3V line might work, and clearly it does for some people's cases; but it isn't possible to generalise from one or two cases. The 3.3V line may or may not have adequate spare capacity for a particular fan.

David

Yup. I've revived a lot of fans with a few drops of 3-in-1 oil.

I imagine a fan works fine off the 3.3v line if the only things drawing power are the Pi and a fan, but for those who also have one or more hats I wouldn't dream of powering a fan off the 3.3v line. It's too easy to add a resistor or diodes, as mentioned above, and power from the 5v supply.

Sewing machine oil can be either natural, synthetic or petrochemical. I'd use synthetic (silicone), but not the other two, esp not natural. Natural oil ages, oxidizes and evaporates over time. Good luck if the can the oil comes in specifies what's what.

I'd also use a fan with ball bearings, not sleeve bearings.