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Old 23-12-2013, 08:02   #1
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12volt to 6 for a heater blower...

I have a mr buddy heater with a Built I 6 volt blower fan. I want to plug this into any 12 volt receptacle around the boat. I bought and wired a circuit with a reducer from radio shack that was rated to 1 amp. It worked twice. The temperature was sixty and now it's zero outside. The fan is rated to draw 900ma. I think that regulator is not rated high enough, is that why it stopped working? When I plug it in now All you here is a buzz as though the fan is trying to start.

I bought a 3 amp rated product from bwd auto part manufacturing and the wiring schematic is counterintuitive, even though I called the manufacturer. The schematic shows that if the amp load is 1, I need 4 vr1 voltage reducers wired in series. If the draw is 2, I need 2 vr1s. 4 amp draw and I need 1 voltage reducer. The tech guy at bwd said I can try using one reducer but should check the circuit with a multimeter.

What should I check, the voltage coming out or the ohms or both. If I wire this up and the volts read 6, can I use it or would it damage the fan?

Am I making this too complicated? Is there a simpler solution? Moving the boat from Lake Superior to the exumas isn't out of the question.

Thanks
Christian
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Old 23-12-2013, 08:35   #2
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Re: 12volt to 6 for a heater blower...

Your latest voltage reducer is a simple bank of 4 resistors. You want enough resistance to drop the voltage 6 V at 1 amp. In other words 12V in and 6V out.

Ohms law says that E(volts)=I(current)*R(resistance in ohms). So it takes an R of R=E/I or 6/1=6 ohms to drop the 6 volts for your 1 amp current draw. If you were drawing 4 amps it would take 6/4= 1.5 ohms. So the more current you draw the less resistance it takes to drop 6 volts. That is why it takes more resistor elements for your 1 amp draw.

It is counterintuitive, but it fits with the science.

So, hook up 4 resistor elements and plug in your heater fan. Measure the voltage to the fan. Should be near 6 V. Anything from 5 to 8 V will probably work fine too.

David
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Old 23-12-2013, 08:50   #3
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Re: 12volt to 6 for a heater blower...

It would be more efficient to replace the fan with a 12 volt unit.
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Old 23-12-2013, 08:57   #4
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Re: 12volt to 6 for a heater blower...

Note: measuring voltage requires the fan to be hooked up and running. If it is not running and drawing power you will measure 12V.

DC-DC converters are real cheap from China - usually a fraction of the cost of the parts if you were to buy them .... and that is delivered to your door. A 12V to 6V unit is probably less than $5 and will not generate all the heat your resistor solution would.
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Old 23-12-2013, 09:04   #5
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Re: 12volt to 6 for a heater blower...

The resistors are $8 each. $32 in resistors seams like a pricy solution. I am having a hard time finding a product that reduces for less.

Also the fan is built into a housing as part of the heater.
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Old 23-12-2013, 09:39   #6
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Re: 12volt to 6 for a heater blower...

This may help or it may not
http://www.summitracing.com/parts/sm...FSVgMgodDHkAKw
Should be able to find at good auto parts store
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Old 23-12-2013, 10:09   #7
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Re: 12volt to 6 for a heater blower...

That's exactly what I have. I need to buy four of them for one amp draw.
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Old 23-12-2013, 17:44   #8
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Re: 12volt to 6 for a heater blower...

Quote:
Originally Posted by Ketchgould View Post
The resistors are $8 each. $32 in resistors seams like a pricy solution. I am having a hard time finding a product that reduces for less.
ZH2A DC DC Power Converter Regulator Module Step Down Adapter 12V 24V to 6V 5A | eBay

$6.63 ea, shipping included, good for up to 5A (and probably about 3A without extra cooling)

This is just a quick look, there might be cheaper ones available.
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