Interior lighting - Confused?

Hi All,

Quick question regarding interior lighting concepts, probably an easy one if you do this day in day out, so I've provided a short version and long version in case you need more detail. Any help appreciated!

Short Story:

With interior lighting activated from ground switches, is it common (with bulb removed) to have a 12v feed on one side of the bulb holder and to have voltage (7v) on the other wire on a Ford, or is this indicative of a problem elsewhere?

Long Story:

I have been having some electrical issues on the rear of my Ford Focus 2001. I removed a bunch of trim and discovered a grey connector which joins one harness to the other and unfortunately, the corrosion is so bad, it's literally rotted away the terminal connector pins.

So I'm looking to solder everything manually, I'm not too worried about retaining the original connectors however, there is a function for the internal lighting in the trunk which has never worked since I owned the car that I would like to get working again.

On the male side of the connector (coming from the front of the car), there is a black/blue wire that routes from there and into the luggage compartment bulb holder. I removed the bulb and conducted a voltage measurement on this wire and it's reading around 7v (battery voltage is 12.4v). On the other side of the bulb holder is another wire (blue/orange) which from the schematic, should be the main power feed and is reading 12v when testing.

Going back to the connector however, where the black/blue cable is, there doesn't seem to be anything connected to this cable on the FEMALE side of the connector. Looking at the schematic, is shows that this should link up to another black/blue wire that comes from the trunk lock itself (which provides a ground when the trunk lid is open - and therefore the light should come on).

Inspecting my trunk lid lock however, I only have a black/orange wire coming out of it which then runs back to the corroded connector, but mates with another black/orange wire on the other side which I believe goes directly to the central locking module (possibly for anti-theft)?

If I am going to solder things up, I'm wonder whether this is actually a common design for how internal lighting works. I connected the black/blue cable up to the black/orange cable from the trunk lock lid and I can confirm that this does activate the bulb when the trunk lid is open and turns off when the lid is closed. The question is... Should the black/blue wire going into the bulb holder have 7v feeding in? I don't want to solder it up permanently and potentially cause damage to wiring or worse (burn my car to the ground).

If you're interested to see the wiring diagram I am using you can see it here: navody.ford-focus.cz/Ford_Focus_manualy/mk1/FF1_el_schema.pdf

Interior Lighting: Page 371
Corroded Connector: Page 704 (Connector C48) - 14A584 (Female) / 14014 (Male)
Trunk Lock Connector: Page 763 (Connectors C798 / C800) - Though the wiring on this doesn't match what I have, probably due to spec?

Any help appreciated!

From what i can tell this pdf. File is for a 2002 focus not a 2001. So that would explain the differences in wiring colors. I would recommend you go to www.eautorepair.net and sign up for a subscription for your car as the wiring diagrams are grouped together for parts of the car. So you won't have to flip through 800 pages to get to a specific diagram. This should make it 100 times easier for you.

Not only is the wiring diagram for an '02 it also looks like it's for the euro cars. The OP sounds like he's in the US. Getting the correct MY and market wiring diagrams would definitely make this easier.

Regards 7V on black/blue that wire may land on the GEM. So the 7V could be either for monitoring the circuit or a bit of leakage.

Apologies, I really should have mentioned that I am based in the UK which is why I was looking at a euro schematic. I did include that detail originally, but I deleted it while I was formulating my original post d'oh! I blame the heat we've been having for the brain fart!

Anyway, I managed to fix my issue and have everything working! But that wasn't before I managed to blow a couple of fuses and then spent half the day wondering why the heck nothing on the rear of the car was working haha! Oh well, lesson learned! Thanks for the help guys!