Running dedicated wire to battery for Cigarette Lighter - PeachParts Mercedes-Benz Forum

ps2cho · #1 11-24-2009, 11:26 AM

I have no power at my wire and I don't want to pull up the entire dash to chase the wire..All my fuses are intact.

Can I just take a new wire from the battery to the cigarette lighter directly?

I understand I will probably need a fuse to protect anything I hook up to it. What type of fuse would be adequate for this job? I have some leftover 8gauge wiring that I used to wire my subwoofer...would this be okay to use or should I get some proper electrical wiring?

Thanks,
Robert

gmercoleza · #2 11-24-2009, 11:55 AM

You should be fine as long as there is a fuse in place. Size of the fuse really depends on what you plan on running on that curcuit. Keep in mind the circuit will always be active unless you install a relay that keys off the ignition key...

RadioTek · #3 11-24-2009, 01:32 PM

You might be able to locate a vacant 'always hot' output terminal on the fuse block and power it from there. Alternatively, you could tie into an existing 'always hot' and add a fuse.

I would try to find the cause of the problem, but I'm kind of Psychotic like that.

PaulC · #4 11-24-2009, 02:17 PM

If you do run it from the battery, use an inline fuse holder wired as close to the battery as possible for maximum protection. Often, a cause for a short in a situation like this is a chafe in the wiring insulation in the area where the wire enters the passenger compartment. If the fuse is located beyond this point, you can still fry the car and the fuse would not blow.

You really have to have your wits about you when doing aftermarket wiring.

I recall a time in the early '90's when I had a permanent cellular phone installed in one of my cars. The installers were kind enough to mount the hot wire in the vicinity of the foot-operated parking brake, and had misinstalled one of those jumpers that clips onto a fuse in the fusebox for power.

I took delivery of the car from the phone installer, drove it home, and parked on a hill. I set the parking brake, heard a loud sizzle, and the interior of the car instantly filled with black smoke. I had the presence of mind to immediately release the brake, which ended the short, and just had a slightly-melted fusebox for my troubles. I had an earnest discussion with the installers.

ps2cho · #5 11-24-2009, 08:57 PM

Ok thanks guys. I plan to run my GPS off it, that's about it. What amplitude fuse would be adequate for this? 3amp? 12amp? higher?
There was a red wire that was hardlined to the battery that went down through the firewall when I bought the car...it went to nowhere and still to date I have no idea what it is for. It already had an inline fuse so I just extended the wire to the CL and it worked a charm.

I will rarely use it, but when my GPS is out of battery it could be a life saver...It's just nice to say it works.

Angel · #6 11-24-2009, 09:57 PM

I like This chart - just assume you have 60C copper wire

If you cant tell what size wire you have (if its not printed on the outside), just go with a 10A fuse to be safe - that'll power most anything you'd plug into a CL. Your GPS probably only requires 1 or 2A to run/charge.

Please tell me that the fuse is on the battery side of the firewall...a 12v car battery can make a LOT of heat if you short it the right way.

-John

mgburg · #7 11-24-2009, 11:50 PM

Unless you're replacing the wiring that CURRENTLY powers the CL, I'd leave the circuit as is and run a secondary CL/Convenience Circuit with FT power...and as has strongly been suggested here, fuse that particular wire at/near the source of juice...right at the battery.

Most components will let you know what current is required to power their gear...unless you intend to run a laptop, 12V. refrigerator and an 800 Watt power-inverter from that particular outlet, make sure the fuse doesn't carry more current than the wire itself can safely handle...i.e.: size the fuse BELOW the wire's capability.

And, be sure you have a safe, sound and solid ground. Nothing works well if the grounding sucks.

Also, stay away from Slow-blow fuses. Unless your GPS is a current-sucking startup hog (and it isn't), you don't have a need for that type of fuse to begin with.

Your GPS? Fuse it at 5 Amps. and you'll be fine.

Watch where the wire goes, no sharp bends or twists and lace it properly and snug...don't "Jack Armstrong" the wire ties...just snug 'em down so the wiring isn't flopping around and you should be good to go.

GL!

ps2cho · #8 11-25-2009, 02:38 AM

Yeh the fuse is a couple inches away from the battery, engine bay side...all good there. I decided on a 5amp fuse and everything is working great.
I'm using the ground provided in the dash, it was only the power wire that had no voltage.

Tomorrow I am going to get my G-Tech Pro on my 260E now I can actually test her

#9 11-25-2009, 08:52 AM

I have installed a female cigar lighter socket under the dash with the charger for my GPS semi-permently installed. I tied it into the hot wire from the ignition switch so it automatically puts the GPS to sleep when the key is off.

Phil · #10 11-25-2009, 10:47 AM

Why not go to the fuse box and find a circuit that is switched by the ignition switch and run your wire from the hot side and add a fuse in line. This way you wont drain the battery when the car is off.

mgburg · #11 11-27-2009, 11:16 AM

Quote:

Originally Posted by Phil

Why not go to the fuse box and find a circuit that is switched by the ignition switch and run your wire from the hot side and add a fuse in line. This way you wont drain the battery when the car is off.

From the original post, he sounds like he doesn't WANT a switched circuit...he wants it "hot" all the time...therefore, running from a non-switched circuit would be nice if it were easy, or running from the battery (properly fused) would be the alternative route.

However...

Running wires from the battery, willy-nilly, under the hood just isn't proper...please lace your "addition" into a "traceable" route under hood...that way, you'll have an easier time looking for, or eliminating, trouble should it rear its ugly head in the future.

mgburg · #12 11-27-2009, 11:25 AM

Quote:

Originally Posted by ps2cho

Yeh the fuse is a couple inches away from the battery, engine bay side...all good there. I decided on a 5amp fuse and everything is working great.
I'm using the ground provided in the dash, it was only the power wire that had no voltage. ... Tomorrow I am going to get my G-Tech Pro on my 260E now I can actually test her

I'd check that "no-voltage" ground wire using an ohm-meter to be sure it truly is ground...

Remember: Switched circuits have no voltage when you have the switch OFF (depending on where you are poking the wire...pre- or post- the actual circuit switch). If you attached your new "ground wire" to a switched-circuit wire, when you turn on the gear, it may not work well, if at all...and there's a possibility that depending on what circuit you made that particular attachment, you could mess up some pretty expensive circuitry with that attachment...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

An "old" electrician truism:

DON'T GO WIRING IF YOU'RE NOT 100% SURE WHAT YOU'RE WIRING TO!!!

A "young" electrician truism:

"OUCH!!! That sucks! I can't feel my hands! What's that smell?"

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Enjoy!