Electrical questions

Hey guys I did some searching around and couldn't really come up with a clear answer so I'll just go ahead and ask.

I've recently started my build, currently I'm working on my interior and plan to get some extras wired up in the next few days. I'm looking at adding 2 extra cigarette outlets, and some courtesy lights (my xj didn't come with any.) For the cigarette outlets, I am under the impression that I can simply tap the power from the factory dash one, and for the courtesy lights, I am under the impression that I can tap from the dome light. Correct? If not, please help me out here, I have a 96 if that helps any.

Thanks!

Bear in mind that most vehicles - particularly about 1990 and later - use wiring that is "just enough" for the design application. This isn't always the case, but let it guide you when making modifications.

Doubling the load (or thereabouts) on that wire is therefore a Bad Thing(tm), and can cause trouble for you.

The best way to do it is to use the wire to trip a relay (which has a coil ON current of usually 100mA or thereabouts,) and the relay can be fed by the battery to drive whatever. The relay is fed by a fused lead, so you have safety that way as well.

Taking the standard Bosch/Hella DIN relay, you'll see the following numbers next to the terminals (and I'll give their functions):

#30 - This is the power feed to the relay. This is where your fused lead runs into, and it's what will power the accessory when the relay is ON.
#85 & #86 - These terminals are each end of the relay's coil. Convention is usually that #85 is the signal that trips the relay (switched lead,) and that #86 is the ground for the coil. Therefore, you'd tap a lead off of the power feed for whatever accessory you're using to drive the relay (cig lighter, dome lamp, whatever...) and feed it into #85. #86 gets grounded at a convenient point.

#87 is the NO (Normally OPEN) contact - this is the one that is turned ON when the relay is tripped, and is OFF when the relay is at rest.

If you have four terminals, this will be what they do. If there is a fifth pin (usually in the centre of the underside, amid the other four,) it will either be #87 (NO) or #87a (NC, or Normally Closed. ON at rest.)

A relay with two #87 contacts can be used to switch two accessories ON and OFF at the same time, while the #87/#87a is used as a "changeover" - sort of a Logical OR (Pin 87 OR Pin 87a will be on - never both, unless the relay is AFU.)

The centre contact, whatever number it is, may also be ignored and any of these relays may be used as a "four-pin" relay. Simply do not wire the central slot.

If you need relay blocks and relays, hit me backchannel and I can help you.

It does make a big difference whether you plan to run cig lighters or ipods in those sockets. Cig lighters draw a lot of juice.