Is my car exploding soon?? Fuse tapping

Goal: Turn off cig lighter socket when the car / engine is off (for my bluetooth dongle) Method: Add-a-circuit between A8 (sockets) and B9 (CU telephone) - see pic Based on my research (on this site and others): 1. B9 is not used (as I do not have a car phone) and is switched 2. The "bottom" slot / tab is HOT 3. The outside tab of the add-a-circuit should go into the HOT slot However, when I connected "correctly" (i.e., exactly opposite of what's shown in the picture below), the socket didn't even get power. In addition, when I plugged in the add-a-circuit the other way, the plastic panel won't close. Then I proceeded to "reverse" everything - i.e., connect to the top slot of A9 and "reverse" the add-a-circuit as shown below. Then the socket works exactly as I intended (only powers on in acc mode / engine running). Since my electrical knowledge is limited to turning on / off a light , wanted to confirm with the experts here to ensure nothing will blow up in the future. Thanks!

@Hoster987 - I think you'll be just fine here. The direction of how you plug in the Add-A-Fuse shouldn't matter. You're tapping into a positive lead (same +12V on both side), and branching off Switched +12V for your Bluetooth™. Just plug it in -- in whichever direction fits best. You probably just didn't have a solid connection the first time around. If it will make you feel any better, note that some fuses are likely inserted upside down and don't have (+) or (-) markings on them. Your car won't blow up! Guaranteed!*** ***Not necessarily a guarantee. Some restrictions might apply.

I can't guarantee anything for you, but I recall running into something like this with my car as well. I then probed it out myself and understood it more clearly before setting it up on my car, because I'm annoying like that. I don't remember the details at the moment. I don't have a current picture of my setup either, and it's cold out, so I don't know where I left it... but I can do that if required. Fact is, worst case, you might be pulling your power for a circuit through two of the tapped fuses... in other words, one circuit may have two fuses in-series from your tap. Since both are the same in your picture, that won't matter... but you may blow both if you overload the circuit, that's all, so be aware of that... but it won't be any LOWER than previous, so that's unlikely to happen... so you should be fine. As above, I guarantee it! (Not really!) But if you're worried, you are welcome to give me your car and I'll take the risk for you, no problem.

Pulling a "cigarette lighter" connection from another point is a bad idea. Most other circuits are not designed for the current (some other person) may plug into such a connector, even if you intend it to be low current. Better solution is to put a relay in the circuit, and use the low current lead to drive the relay.

Very valid point, but since there is a fuse of the same size as the circuit, it should be fine... if it was larger, then yes that would be a concern. That being said, it would be better to use a smaller fuse on the lighter circuit, especially if it's drawing less anyway. In other words, generally speaking, you want your fuse to be a little above the draw you expect. So, if you're running a 1A device, you shouldn't use a 15A fuse... maybe something more like 2A or so is preferred. But, as you can see, in most cars the lighter socket is setup for 20-30A, and most people use a small load (charger, etc). The manufacturer can't know what you're using, so they have to size for max allowable... and that's considered OK for the most part... so this is just duplicating that, so it seems fine.

As long as the point you are picking up the power from is also good for the current.

Excellent point @N_Jay ... fuse B9 is designed for 7.5A, so @Hoster987 we both would recommend down-sizing the fuse to that level, since the source circuit isn't designed for 15A (your current fuse). I incorrectly assumed that you checked that, but per http://howtoporsche.com/cayman/987c...c-2005-2013/2005-to-2013-cayman-987c-fuses-box-diagram-location-amperages-list/ says that socket was designed for 7.5A... If you don't have a 7.5A fuse, you can go lower, of course.

Thanks for the advice. I actually reused both 7.5amp fuses from A8 and B9...those two are inserted into the add a circuit. I don't think two 7.5 amps make a 15A circuit / fuse, correct?

I think I have two Add-A-Fuses in my fusebox; one of which is to power my radar detector. I'm pretty sure that the Add-A-Fuse design separates the two fuses (one for the original fuse, the other for what's being tapped) -- it's just important to know which one fuses what (I forget). The second Add-A-Fuse might power my reverse camera? In @Hoster987 's case, I think that a Bluetooth adapter won't draw much off the switched power line -- so I'm not too worried here. If this was a situation where I'd be wiring something that requires a lot of juice (ie, a headlight), I'd definitely tap in a relay (ideally solid state) that requires very little power -- and have the main connection tapping directly off one of the main power leads and in-line fuse that. That's just me and YMMV.

I'll just add.. if you find you need 12 switched on the windshield header (at least on the Boxster , I assume Cayman is the same) - there is switched 12V going to the two sunvisor mirror lights. If you remove the header interior cladding the wiring will be obvious. It's worth using a voltmeter to check polarity..