AC/DC 14V to 12V voltage converter

[KingK0ng]

Hello everyone, i plan to install a 12v 40mm fan on my 2 din head unit. Note that i'm not going to use the complete ashtray trim anymore and relocate the cigar lighter somewhere else. Since the ashtray bulb wouldn't be useful anymore i thought to pick up power from the bulb wires to power my fan ( see picture ). Thing is the bulb is listed as 14v but i don't know how much voltage the wires give and if the voltage is constant or not. Any  idea ?

If i can't get 12v stable from this source i though to get a voltage converter, something like input 8-36v to output 12v 1a. Problem is some converters are listed as AC/DC and others as DC/DC and i'm totally green on this matter. In case i can't pick up directly from the bulb power source which converter type should i choose bewteen both ?

Any input would be appreciated.

[hughezee]

1 hour ago, KingK0ng said:

Thing is the bulb is listed as 14v but i don't know how much voltage the wires give and if the voltage is constant or not. Any  idea ?

I think you will find OEM bulbs are labelled 14V and I have replaced hundreds over the years with standard 12V never any issues and I can't imagine fitting a 12V fan with its own fuse will be an issue. However, you are probably better off using a circuit that doesn't work until you switch the car lights on, a spur from the cigarette lighter would be better option?

[KingK0ng]

Again don't know what continious voltage those wires give but isn't using 12v on 14v source reduce the life span overall ? Yes i though about using a source where it works only when the radio is on.

Is the fuse an absolute necessity in this case and if so why ? and what is a spur on the cigarette lighter ?

 

[KingK0ng]

16 minutes ago, KingK0ng said:

Again don't know what continious voltage those wires give but isn't using 12v on 14v source reduce the life span overall ? Yes i though about using a source where it works only when the radio is on.

Is the fuse an absolute necessity in this case and if so why ? and what is a spur on the cigarette lighter ?

 

Ok i searched for the spur signification, no i can't since i'll use the cigarette lighter as a double usb port.

Edit : The ashtray bulb is working from position I to II, so it should be good no ? Why did you mention "until you switch the car lights on", don't understand what the lights have to do in this. Can you elaborate ?

[KingK0ng]

After some thoughs, if i'm not mistaken our 12V outlet give power only from acc to start, not when off, correct me if i'm wrong, otherwise i'll check once i get to the car. Now what i could do is buying another usb port with 3 outputs. Two would be 5v 2.4a for other stuff that i need and the third would be a qualcom 3.0 with the possibility to output 12V / 1.5a. In this case i could use this particular port for the fan. I guess would be much easier to setup this way and no need for fuse etc.., your thoughs ? 

[hughezee]

1 hour ago, KingK0ng said:

Again don't know what continious voltage those wires give but isn't using 12v on 14v source reduce the life span overall ?

Firstly it is a 12v source not 14v the 14v bulb is just for longevity.

1 hour ago, KingK0ng said:

Is the fuse an absolute necessity in this case and if so why

Since you were prepared to protect a relatively inexpensive fan with a 12v converter, a low amp fuse would be a good start?

1 hour ago, KingK0ng said:

Ok i searched for the spur signification, no i can't since i'll use the cigarette lighter as a double usb port.

I wasn't aware of this and it was only a suggestion.

1 hour ago, KingK0ng said:

The ashtray bulb is working from position I to II, so it should be good no ? Why did you mention "until you switch the car lights on", don't understand what the lights have to do in this. Can you elaborate ?

All the interior instrument clusters, climate control, clock, ashtray illumination or backlights only come on when I switch the side/ headlights lights on, maybe yours is different?

[KingK0ng]

53 minutes ago, hughezee said:

Firstly it is a 12v source not 14v the 14v bulb is just for longevity.

Ah very intersting, thanks for confirming the 12v source.

53 minutes ago, hughezee said:

Since you were prepared to protect a relatively inexpensive fan with a 12v converter, a low amp fuse would be a good start?

Thing is i just wanted to be cautious in case it was 14v on the source which thankfuly it isn't like you mention. So I didn't want to reduce the lifespan of the fan and have to replace it every and so, plus avoiding the process of removing the radio again etc.. For this matter i'll use a Noctua fan for their quality. 

So the purpose of the fuse you suggest is only to protect the fan ?

53 minutes ago, hughezee said:

All the interior instrument clusters, climate control, clock, ashtray illumination or backlights only come on when I switch the side/ headlights lights on, maybe yours is different?

I don't smoke so never use the ashtray, but from what i remember and if not mistaken, the ashtray bulb was always on but i may be wrong..my ashtray is off the car right now. I should try to plug it in and check it again. If like you said it turn on when lights are on then it won't be the best option for sure.

Edit : When i say always on i mean even lights turned off.

[KingK0ng]

Checked this morning, ashtray bulb don't light up on position I but does when lights are turned on so you where right. So this source won't work for my purpose. Like i said in one of my message i'll use a usb port with 3 output and port with qualcomm 3.0 ( 12v/1.5a ) will be dedicated for the fan.

Now i have another question, in order to have two lights it is possible to add another 14v bulb to the existing ashtray bulb wires ? I mean can two bulbs draw power from a single 12v and ground wire without causing issues ?

Illustration

[welland99]

Why is a fan needed at all? Are you worried that the new head unit will overheat?

[KingK0ng]

Whenever i can improve the cooling of my electronic devices i just do it. I've done this for my amplifiers, monitor speakers heatsinks and external soundcard ( heatsinks only not fan ) and etc..

Another two reasons is that i wanted this very specific head unit, it's a non premium brand and may be extremely difficult to get if discontinued. So to preserve its life as much as i can and because quality may be questionable i though adding a fan could only benefit. Second reason i may move soon to another country where weather can be extremely hot.

[KingK0ng]

On 4/22/2022 at 11:30 AM, KingK0ng said:

Now i have another question, in order to have two lights it is possible to add another 14v bulb to the existing ashtray bulb wires ? I mean can two bulbs draw power from a single 12v and ground wire without causing issues ?

Illustration

I'm going to pick up some parts in the next coming days. Does anyone have an idea if i can do that without any issue ?

[Logohotrod]

Not sure what your are trying to do but hope this helps . You need to know what wattage you intend to use for the additional bulb . Check out Ohms Law .If the same low output as an ashtray bulb most vehicle manufacturers build looms with thinner PVC outer insulation to shrink looms but the core will still carry a little extra current and an extra low wattage bulb for a guage or LED with built in resistor or 12-14V , rating will be fine .If you intend to go much higher in light output look for a larger higher current wire that operates from the same ignition on source e.g. "power point" or old the cigarette lighter supply or other key position 1 point .