Can you safely use a lower voltage on a DC motor?

Question

I have some pepper seedlings I'm starting indoors and I'd like to set up an oscillating fan for ventilation. I found an old one in my garage meant to plug into the cigarette lighter of a car. It's rated 12VDC 0.8A.

I cut off the end and wired it to a 12V 3A LED power supply and it works, but it's very powerful and there's no speed adjustment. I have a box full of power supplies and the two that I think might work are a 6VDC 1.66A adapter and a 7.5V 2.1A adapter (I couldn't find a 9V one powerful enough). I know a the motor can draw much more than .8A at startup, so ideally it should be double, but I wanted to know two things:

1) Can I run a 12VDC motor on 6V or 7.5V without burning up the motor (or my home).

2) On an unrelated note: if I had a 9V 2A and a 9V 3.5A power supply, they'd act the same in regards to the motor, right? It just draws what it needs?

I've tested both supplies on fan and both start it fine. I tested a 12V 1A power supply and it failed to start the motor.

Thanks for any assistance you might be able to provide on this project.

Answer 1

1) Can I run a 12VDC motor on 6V or 7.5V without burning up the motor (or my home).

Yes, the fan will likely spin slower (that's fine for your needs) or it may not spin at all (in which case, you need a higher voltage).

2) On an unrelated note: if I had a 9V 2A and a 9V 3.5A power supply, they'd act the same in regards to the motor, right? It just draws what it needs?

Yes. See here. A device will draw the current it requires and no more, regardless of the current rating of the motor.

Answer 2

If the motor starts fine, you should have no problem with the lower voltage supplies. Reducing the speed of a fan reduces the load on the motor, so once it is running at a steady speed, the motor will draw less than rated current.