12 Volt Power Source

[rsiwicki]

okay....I have the little yellow box that recalibrates the speedo to account for my 4.08 rearend that apparently is here to stay as I have not had any problems yet.

I need to find a 12 volt power source that comes on & off with the car for the speedo calibration unit. I know this is a dumb question, but where do I find a simple 12 volt source? Can I jump a wire off the fuse box inside the car? I use to be able to do this stuff easily enough 12 years ago when I was 20 and knew how to wire up car stereos....but my patience has long gone bye bye.

It says the unit draws very little current, but does not make mention of a fuse/ampage limit or to say to put an inline fuse to the unit. Says to just hook it up to a 12 volt source.

[elwesso]

I would be iffy about tapping into anything in that area where the transmission is located.. Personally what I would od is get like some 10-15gauge wire and run it from the battery...

[rsiwicki]

if I connect it straight to the battery....will I run the risk of giving it too much juice??? Would I not need to put in something like a 10amp fuse to limit the juice to the little thing? I don't want to fry the electronics.

[elwesso]

Thats why I said use a small wire... 15 gauge wire is about what most speaker wire, to give you a size.....

12volt things only use what power they need... Its not like your going to be feeding it too much power, because it only takes what it needs. 12 volts is 12 volts, whether or not you tap it from the fuse box or directly the battey.. The reason you have fuses is for shorts... When the fuses are in place, its just like it being connected directly to the battery... The fuse then breaks if something shorts or its drawing too much current...

Still may not be a horrible idea to tap it from something in the fuse box in case the wire breaks and shorts out.. There should be some empty slots in the underhood box that you could use...

[szh]

Wes is right. Doing it straight from the battery will not fry it per se.

However, some things to keep in mind. Having a fuse in-line never hurts and, more importantly, you probably want to wire it in somewhere where it only draws power when the car is on, right?

Z

[97Q45t]

There's a large chance that the Yellow Box use a 7812 12V IC Voltage Regulator. The 7812's MAX drawing current is 1A so a 2A fuse inline with the circuit would be good.

I doubt that the circuit uses even half of the 7812's 1A capability. Since the drawing current for the Yellow Box is so small, tapping into any existing system (i.e. stereo) would be OK if that's easier for you.

Did you email the Yellow Box manufactuter about the fuse? I bet they'd know about maximum drawing current of the circuit.