Lotus Elan

Needle in haystack wiring issue

PostPost by: bertavfc » Wed Aug 15, 2012 12:54 pm

Hi, having been working through some electrical/ignition gremlins I found a loose wire in the passenger footwell of my '69 +2, it appears four black wires come through the bulkhead from the engine bay and are joined via bullet connectors to one black presumeably high load wire (by size). judging by the length of said wire it doesn't appear to go into the main crop of bundled wire that goes off into the dash (seen on the right), it's very difficult to trace but I believe one of the wires is the live to the fan stat, I understand this is a real needle in a haystack situation but if anyone has an idea it would help an awful lot, best regards, Rob.
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PostPost by: Jason1 » Wed Aug 15, 2012 1:34 pm

Black ones are usually earths.
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PostPost by: jono » Wed Aug 15, 2012 2:08 pm

Not always, quite a few blacks are lives as I recently found when wiring my dash and other parts of the car - confusing :shock:
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PostPost by: bertavfc » Wed Aug 15, 2012 2:16 pm

If it helps the wire in question appears to be a wire within a wire?, an outer core with a separate insulated inner core, both wire materials appear different (one copper, the other tinned), very confusing?.
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PostPost by: jono » Wed Aug 15, 2012 3:44 pm

......that sounds like a screened cable but I can't think what it might be for?

I have just fitted a complete new wiring loom to my +2S and there are no cables answering that description. Perhaps it's a PO's modification?

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PostPost by: stugilmour » Wed Aug 15, 2012 3:47 pm

Rob, that does look like a bit of a mystery. I guess the smart Alec answer is plug the whole lot to ground and see what blows up! :)

Can you confirm your model and if the car is RHD; i.e. passenger side is the left side of the car? Do you just have a single two fuse box under the bonnet or the more elaborate set-up?

As stated, Black is typically ground in the loom runs, although some component wires (like the heater motor, radio, window motors, etc.) may be black to where they join the loom. Can you check the wire and see if there is no resistance to ground?

I checked the wiring diagram for my '69 Federal LHD, and there does not appear to be any legitimate black grounds going through the firewall to the engine bay (except maybe grounds associated with the headlight microswitches located in the dash on the Federal cars, which is a whole different deal). This makes sense as in stock form as there is a grounding bobbin on the left side of the engine bay, and another ground bobbin on the right body mounting bolt just behind the dash mounting bracket. I am going off of my Federal diagram because it shows the physical location of the connectors rather than purely schematic diagram. If the grouping of black wires do in fact go through the firewall I might suspect PO ran extra grounds, but this is completely a guess.

When you mention the 'fan stat', do you mean the radiator mounted Otter switch sensing coolant temperature for the engine electric fan? If so, I can't help on that one as I just noticed it is not included on the Federal wiring diagram and the entire section K Cooling is missing from my Workshop Manual. :shock:

Good luck with it. Should be able to figure it out with a bit more info.
Last edited by stugilmour on Wed Aug 15, 2012 4:05 pm, edited 1 time in total.
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PostPost by: stugilmour » Wed Aug 15, 2012 4:04 pm

bertavfc wrote:If it helps the wire in question appears to be a wire within a wire?, an outer core with a separate insulated inner core, both wire materials appear different (one copper, the other tinned), very confusing?.


Rob, is it sort of like a coaxial cable similar to an antenna wire or cable TV type deal? If so, are the two connectors in the pic separate and one wire pair to the shielding and one pair to the wire inside? Does look more and more like PO mod like Jon says.
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PostPost by: Orsom Weels » Wed Aug 15, 2012 5:07 pm

I've come across some old radio's that have used that type of cable for the speaker, the inner wire being positive or 'hot' & the outer forming an interference shield & acting as the earth/negative. (Swap the poss & neg above if your car is positive earth) Can you trace where the two wires that it's connected to go ? Do they run to a component or do they have continuity to earth ? Indeed, are they common or separate ? It wouldn't be uncommon for a speaker to have two black wires running to it although originaly one would probably have had a trace colour running down it, mostly white, which could have dissapeared over the years.

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PostPost by: bertavfc » Wed Aug 15, 2012 7:03 pm

Ok, this rings true, the PO had a converted turnlock installed (FM+MP3), perhaps this is a redundant wire?, although I'm a tad vexed why it goes through to the engine bay, many thanks for the ideas, will dig a little deeper, regards, Rob.
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PostPost by: rdssdi » Wed Aug 15, 2012 7:52 pm

If you determine this is an original wire rather than a PO item, look through the worksop manual schematics. They list them according to LHD or RHD and U.S. and dates of manufacture. It is possible that you could find the schematic that matches your wiring loom.

It would then be possible to determine what those wires are.

Bob
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PostPost by: tcsoar » Thu Aug 16, 2012 11:06 am

Hi,

The four cables look like they may be speaker cables, two pairs of moulded together cables and quite a bit smaller than the others in your picture. Linking one from each pair together and then connecting to the cable you described as having two conductors insulated from each other was probably a DPO mod to connect the radio to the speakers, although this may be an original Lotus method :roll: I wouldnt have thought so.
Mine had four cables similar to yours in the original loom although they did not pass through the engine bay. Have you had a look in the boot under the parcel shelf as this was where the original speakers were mounted, and where my speaker cables eventually reappeared from the loom that goes to the fuel gauge sender and boot light.

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