Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - Accessory wiring

I've got a 2004 TF160, and I want to put an electrical connection in for a PDA holder. The easiest place is the cigar lighter, but that's on all the time, even with the ignition off. I want a circuit that works only when the ignition is on. Where's the best place under the dash to hook in to a switched circuit without causing fuses to blow? I notice that there's some unused spaces on the fuse box. Is it possible to put a feed onto one of those, and if so, what's needed from the spare parts bin?
David Dewick


Pull out the centre air vents and patch in to the live feed for the radio. Best of both worlds - it's switched but doesn't need ignition to be on.
John Ponting

>> Best of both worlds - it's switched but doesn't need ignition to be on. <<

How does that work John?
Rob Bell

I think he means 'it's switched but doesn't need the engine running'. Thinking about this I don't know if there is anything except for the fuel pump which is dependant on the engine running
Will Munns

you can easily draw enough current for a few PDAs from here (1 or 2 amps max), but I wouldn't want to pull normal cig-lighter amps from here (10amp)
Will Munns

I see - it needs to be on ACC position II.

The radio has two power supplies - one that is swiched, and another that is always live (to maintain security codes etc).

2004 TFs have a different harness to the earlier cars - but I presume that the colour codes are the same? If they are, then you need to look for the light green wire with the white tracer... (Will will correct me if I'm wrong!)
Rob Bell


Thanks for the suggestion. My only concern is that the radio is a becker low-line satnav and has bucketloads of connections, and then, even if I can see my way through the maze of wires, which do I pick? Can I assume that any wire that's all black is ground, and how do I identify a live feed?

The reason for wanting to set up the PDA is to let me use TomTom instead of the becker unit. The becker's actually quite good when you get used to it - the voice directions are a little teutonically clipped, the maps are more out of date than TomTom, there's no real advance route or itinery planning, and postcodes are only the first 4 charatcters, but otherwise it's quite usable. But, having a map displayed tho' is really valuable, so that's why the PDA's going in. I can't see yet how or where to get becker map updates, and although I think there's one out soon, there's no costs shown. I bet it'll be expensive.

When I fit the PDA cradle, I want to make sure that the cradle and GPS receiver are turned off when the ignition is off so they don't drain the battery when the car's not in use, which is why I wanted a feed that's linked to the ignition.

David Dewick

Hello Rob

I can see I'm far too slow at typing :-O You're right about the 2004 wiring as I've also got automatically locking doors too, that lock shortly after the engine starts. Scared the living daylights out of me the first time I heard the locks go when I picked the car up, and means you can't get out of the car with the engine running. I've got a copy of Dieter's diagrams, somewhere, but I'm not sure what model they go up to.
David Dewick

2001 I would say David (I've also got the 2001-2003 wiring diagram as a pdf, but that's not of a great deal of use to you) - but I would look at the LG/W wire - as the colour codes are almost certainly going to be the same. A multimeter should reveal whether the feed goes to 0 on switching off the ignition.

Has anyone got a post 2004 TF wiring diagram???
Rob Bell

I've got to pop up the road to the MGF Centre in a few days to pick up some "bling" - chrome and Royal Blue are just made for each other - so I'll ask for some help when I get there.

I really miss the MP3 player from the old TF tho'. Anyone know how to get MP3 music from a PDA into the radio? The Becker iPod connecter is a small ransom, even if it did fit into the model I've got, which it doesn't.
David Dewick

for BMC cars green or white means switched with ignition, purple or brown means always on, the strips indicate which circuit the wires lead to (ie which fuse and some switches).
Totally Black wires are ground, black with a stripe are switched to ground by $something

White with red stripe : starter from ignition
black with white stripe : tacho, switched by points(or electronic equ)
Green with red stripe : indicators (RHS?)
Green : with ignition +ve
Purple with black stripe(?) : curtosity lights
Will Munns
Will Munns

for these units (apparently)
Becker Mexico 4337
Becker Mexico 7803
Becker Monza MP3 7882
Becker Monza MP3 7885
Becker Monza MP3 7886
Becker Monza MP3 7887
Becker Monza MP3 7889
Becker Mexico Pro 4625
Becker Mexico Pro 4627
Becker DTM High Speed 7910
Becker DTM High Speed 7913
Becker Traffic Pro High Speed 7820
Becker Traffic Pro High Speed 7821
Becker Traffic Pro High Speed 7823
Becker Traffic Pro High Speed 7825
Will Munns

Something worth checking is if the HU harness has an accessory take off point on the switched live (red) wire as a lot do these days.
This is normally a spare female bullet connector. So if you have one of these its a simple matter of crimping a male bullet connector onto your accessory power wire, and then earthing the other wire in an appropriate place.
Steve White

Will, thanks for the info., the cable from caraudiodirect looks as though it will fit, although it's difficult to make out quite where the wires go into the connector from the photo. Still, it's cheap, so I'm getting one on order.

Steve, where's the HU hareness and connector? I've got two wires hanging down behind the centre console on the passenger side, terminated by orangy-coloured plastic thingys (sorry, but no better description), but not bullet connectors
David Dewick

HU= head unit (radio)

aftermarket headunits offen come with orange for +ve and red for ignition, often they have bullet connectors for broken cars where the wiring is reversed, or where there is no ign wire, in these cases the bullets are often plugged with a plastic plug
Will Munns

Thanks again Will. HU = Head Unit -- doh!! Methinks brain's still addled from the clocks going forward :-8
David Dewick

This thread was discussed between 06/04/2006 and 10/04/2006

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.