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Computer fan powered by car cig lighter? Answered

Ah, so I was doing an Instructable on taking a computer fan and powering via USB, but my fan was rated for 12v and my USB port doesn't put out that much power. But my parent's car puts out 12v, so I should be able to use my fan with it, right? I have the fan, I have a charger for a cell phone that fits into the cig lighter in the car, so it should just be a matter of connecting the wires, right? My fan is rated for .15A, how many amps does a standard cig lighter put out? I don't want to fry the fan (well, forget the fan, I don't wanna mess up the car). Anyone know? Thanks!


I believe you'll need to check the output for the car charger

i agree with zieak on this..

If you simply connect the wires of the charger to the fan, the voltage you will get is definitely less 12v, mobile phone charger supply around 5.7v, 800mA DC (for my nokia at least).
What will be useful in your case is the charger’s connector head, wire it directly to your fan bypassing all the internal components of the charger.

Well it's my brother's old charger, but I have to wait to see if he doesn't need it. So, you think there would be resistors in it?

There would be an entire power supply inside. You would need to open it up and remove everything. Then just pass the wires through. You want the power directly.

Here are a few pics of the inside of it. So basically I need to desolder the wires going to and from the circuit board and then use some spare wire and solder the wires, bypassing the circuit board completely? My brother (who is also into electronics) said that this might blow the fuse. Btw, what is that thing with the coiled copper wire? Many thanks!

Yes. Just remove the board and bypass it. It won't blow the fuse if you don't short it out. The cigarette lighter uses a 20A fuse. Your fan uses 800mA (0.8 amps, less than 1 amp). I would have to see your pictures to know what you're talking about

You say my fan uses 800mA, but on the label (right alongside 12v) it says .15A.

Ah... Sorry... I was looking above at the power supply specs. Your fan uses even less! 150ma, or less than 1/6th of an amp.

Thanks to all who helped! The whole project turned out better and easier than I expected. (and best of all, I didn't get burnt by the soldering iron!). It was fun. 'Cept, the fan puts out a really soft breeze. I expected that, being that it only is meant to cool computer components centimeters from it. I don't guess there would be a way to make it go faster while still being powered by the car, is there? Thanks again!

If it's a 3 wire fan, you can connect the 3rd wire to a switch to the 12v line. When switched in, it should go to high speed.

Curious about a 3 wire fan.. Would it have the usual yellow :12v, red:5v, black: ground? So increasing the speed like you mentioned above would simply mean wiring the yellow(12v) and black, right? Instead of red (5v) and black.. Thanks..

No. A three wire fan is not a dual voltage fan. Pin 1 is ground (usually black), pin 2 is 12v (normally yellow) and pin 3 is the sensor (normally also yellow). A 5v dual speed fan would normally use the colors black, red and white. They are not interchangeable, obviously.

Nah, this fan has only two. But we have a lot of old computer parts around here, so I'll try to find another.

Nice to see that you've pulled it off.. Btw, since the fan only takes 0.15A, you got a few more amps to spare, there's no harm in attaching another fan. You can stick it on top of the first, for as long as the airflow of both fans are in the same direction, you will get stronger breeze.


Reply 11 years ago

Ruh roh. Here are the pics.


The "wire thingy" is a coil used with the regulated power supply. This way your not draining the 7 volt difference to ground. That fuse can remain and should protect the main 20a fuse in the car.


11 years ago

Woops, sorry, you posted above. Disregard this then. Thanks so much!

What did he say, private message me if you don't want to post it here


11 years ago

This question really isn't about . Anyway, I'm 13 and have had 3 uncles and an aunt die from . I know the consequences, and I'm not about to suffer from them.

You can run a 12v fan safely, directly from a cigarette lighter. No conversion of any sort is necessary.

Thanks, exactly what I wanted to hear.


11 years ago

I believe you'll need to check the output for the car charger. If you were to see inside the plastic housing it does the same kind of thing a wall wart does - change the output to match the device.