Lotus Elan

Dashboard Wiring Loom

PostPost by: Breezehill » Tue Jan 12, 2021 1:22 pm

Looking for some info on the dashboard (Facia) wiring loom.

The car is a late 1970 +2S which was running a dynamo but has been converted to alternator.

The question is, does this change to alternator change anything on this dashboard loom or is it all handled by wiring changes on the main engine bay loom?

Thanks in anticipation
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PostPost by: pharriso » Tue Jan 12, 2021 2:17 pm

Breezehill wrote:>> is it all handled by wiring changes on the main engine bay loom?

This!

All the wiring changes are between the Alternator/removed Voltage regulator in the engine bay, no changes in the cockpit or rear harnesses.
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PostPost by: Bud English » Tue Jan 12, 2021 2:53 pm

Unless the ammeter has been changed to a voltmeter as part of the conversion, you may want to do that. I found the ammeter to be pretty useless with the alternator. Getting the unfused high amperage wiring out from behind the facia is a plus also IMHO.
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PostPost by: NedK » Tue Jan 12, 2021 4:09 pm

There is a section of the workshop manual (Electrical, Section M25, p106 onwards) that deals with the generator-to-alternator swap, and what needs to be done. It might be worth referring to alongside the new loom.
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PostPost by: Breezehill » Wed Jan 13, 2021 9:02 am

Many thanks to you all for the responses. Totally forgot about the section in the workshop manual so revisited that last night.

Can I throw one more thing in to the pot. I will be changing the main loom in the engine bay once the dashboard has been completed. Therefore if I replace the engine bay loom for the alternator version, I should therefore fit the dashboard loom for the alternator version?
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PostPost by: alanr » Wed Jan 13, 2021 10:36 am

Just to ensure you are aware.
Both the underbonnet loom and dashboard wiring looms are obviously totally different looms depending on if you currently have the underbonnet 3 fuse box setup ( as mine is '71 +2 S130) or the alternative dashboard central fusebox setup.

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PostPost by: Breezehill » Wed Jan 13, 2021 10:46 am

Hi Alan, it’s the 3 fuse box in the engine bay.
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PostPost by: Bud English » Wed Jan 13, 2021 5:06 pm

Have a look at the wiring diagrams in the manual. For the generator, converted to alternator, cars (both RHD & LHD) the diagrams show no ammeter (or voltmeter) and a splice connection is shown where the meter was shown in the previous years diagram. In the diagram that covers the cars from there up to the +2S 130 cars it shows the battery condition indicator (voltmeter) wired between the B+ connection on the instrument voltage regulator and ground.

I would not assume that the ammeter circuit is the only change in the wiring and order a replacement loom for an alternator car without checking everything else out. On the +2, it's hard enough to find the right replacement harness for your car without trying to find one that might be the one for your modified car. Read a few threads on wiring harness replacement and you'll see what I mean. Also look at the five different choices offered for harness sets by http://www.britishwiring.com/default.asp or the other suppliers.

My March built '70 +2S, although a US car, started out a a generator system and like yours was converted. I think mine was converted by the other owner before me. The ammeter was still wired in and, if the battery was too low, spent awhile pegged at the 30A end until the alternator caught up. I'm in the middle of a complete rewire and replaced the ammeter with a Smiths Classic voltmeter which will look right at home with the other instruments. It's wired in with 18AWG wire and not 10AWG unfused.
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PostPost by: Breezehill » Thu Jan 14, 2021 9:55 am

Hi Bud,

Like yours between me selling it 30+ years ago and buying it back the car was converted to alternator just doing the cable bridge etc and leaving the ammeter in place.

I've rewired from the rear end forward and currently replacing the facia. While this is out I'm going to change the dashboard loom but looking at the condition of the engine bay loom will also change this. Plan is to replace the ammeter with a battery condition gauge, change the facia loom for the alternator version which supports the battery condition gauge and change the engine loom to the alternator version for the +2S

Just need to find a battery condition gauge :-}
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PostPost by: NedK » Thu Jan 14, 2021 10:16 am

+2S 1969 50/2283
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PostPost by: Bud English » Thu Jan 14, 2021 4:05 pm

Sounds like you're on top of it.

I never was a fan of those battery condition indicators, although that is what was used if you're looking for originality. The number markings are fine but the "off charge/on charge" range markings are bewildering and no way indicate the battery condition. A battery "in the green" at 11.5V is just above 10% charge. Not exactly in good condition. If the car is running and you show "in the green" at 11.5V, the alternator isn't in good condition either. :lol:
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