Auxillary power socket in boot. W169

[Biggles1957]

I had a W168 in which I fitted a power socket in the boot. I'm sure I remember there being a pair of wires terminating in a connector behind the left hand stowage compartment in the boot (where the jack etc is stored). I can see what looks like a 'knockout' blank in the plastic liner in the same place in my W169 but before I start making holes I thought I'd ask if anyone knows if the wires are there hiding behind. Reason I'm asking is I've just fitted a towbar and am looking for a power supply at the back end rather than running a wire all the way forwards to the battery compartment. Wiring instructions on the relay box say to connect (via an in-line fuse of course) direct to the positive terminal of the battery, but I think I'd much rather it be on an ignition controlled circuit. I can't really see a reason for it to be permanently live? Any advice much appreciated!

 

[Tony Dyson]

What if you wanted to leave your sidelights on a connected rig with your car locked and unattended?

 

[Biggles1957]

I see what you mean but I only want to tow a little trailer to fetch stuff for my chickens so would never need to do that.

 

[mattkh]

How much current are you hoping to draw from this supply..?

 

[Biggles1957]

Only for a small trailer Matt - so if the brakes and an indicator were on all at the same time that would be 3 x 21W so around 5 amps. I was going to fuse the supply 15A (maybe only 10A).

 

[mattkh]

Thanks.
And the rear sidelights..?
I dont fancy recommending the fuel pump circuit, because in case of an overload, the car would stall.
How about the live to the aerial amplifier in the roof.

 

[EmilysDad]

is there not a SAM or fuse box of sorts at the back of the car without going to the battery? My ML350 (W166) has a fuse box under a rear seat with spare fuse points on the side, both permanent & ignition live.

 

[mioba]

Would the thin wires of a lighter socket be able to handle the current for a trailer (max would be fogs, no plate lights, brakes and indicator) at once I would say.
Be safe OP and check!

 

[Biggles1957]

I completely forgot about side lights! LOL! I guess because I won't be using it very often and the tip isn't open at night! What a plonker! I thought the lighter sockets were fused/wired for at least 15 amps or thereabouts? It's just a bit of a pain running a wire all the way to the main fusebox/battery but I'll have a proper poke around...

 

[mioba]

Just out of interest was there no wiring plug with the tow bar you fitted.
Surely its illegal (but I didnt look) to use a trailer without functioning brake lights and indicators at least.

 

[Blobcat]

@ZZZZ might have some info, although he’s not been around much lately

 

[sonic]

Any wires in the boot will be on the ignition circuit, so when you turn your ignition off you loose your trailer lights.
I would run a cable up to the front of the car for power, too much risk damaging the harness.