Lotus Elan and Lotus Elan Plus 2 Forums

High everyone!

I have finally gotten my new to me '72 Federal Sprint to run but before I can get it inspected I have to get the headlights to work. When I went to check the wiring, I found that there were many wires in the dash and engine compartment that were not connected. There are also disconnected wires that I can not figure out where they are supposed to go to. So far the radio, heater fan, side windows, and running lights work. The headlights, horn, wipers, and signals do not work. I found a brown and blue wire (possibly related to the headlight operation) with a connector on it where the insulation is melted but I can not figure out where it is supposed to connect to. The ignition switch has a brown and blue wire connected and the vacuum micro-switch seems to be too far from the wire for it to reach.

Any help on how to systematically diagnose why the headlights are not working would be greatly appreciated!!!

JAS
1972 Sprint
2005 Elise - sold
1988 Evante - sold

Whoops, I meant "Hi" not "High".

JAS

Hi,
I know there is a downloadable S4 wiring diagram on here somewhere; not sure about a Sprint. Definitely a wiring color code here too. There is also a copy in the Service Manual. If you don't have one, you should get one. Try the search for a Sprint wiring diagram.
This is a great group and I am sure you will get some knowledgeable replies.

Bob

Thanks Bob,

I have a wiring diagram and have been studying it but when I try to compare it with what I see under the dash, not everything lines up. There are wires where there should not be and others not where they should be. Others seem to just go nowhere. The brown and blue melted wire under the dash does not seem to be able to hook up to where the wiring diagram shows brown and blue wires should go.

JAS

I spent hours trying to figure out how the late fail-safe headlights should be wired studying the unclear workshop manual diagram & the many posts on this forum.

Here is the wiring diagram I have put together to help other's with their wiring diagnosis:

Federal_Failsafe_Headlamp_Wiring_Modified_Schematic_V1.13.pdf
(78.13 KiB) Downloaded 572 times


Fail-safe wiring differs in that there are no contact switches on the light pods themselves (even though the wiring is still there), being replaced by twin micro-switches mounted on the dash mounted vacuum switch.

Pharriso (as quoted above) has the best wiring diagram with respect to the Federal S4/Sprint headlights. There are some things on there like the headlight flasher you probably will ignore, as that is a later particular mod.


Basically, the two microswitches do the following:

1. Switch ground to the headlight relays when the vacuum dash switch is pulled. A long black/red wire runs from one of the dash headlight microswitches to the front of the car headlight relays. This long red/black wire will not be found on the new looms that you might purchase. This situation is very different to the wiring diagrams you typically see and different to UK (and I think ROW) cars. Another afterthought factory "kludge" frankly just for Federal cars.

2. Second function is to switch the front parking amber parking lights on when the headlights are on and to activate the dip switch. But, the parking lights also can be switched on independently when the headlights are not on via the rocker switch. Power is jumped from the hot side of the microswitch to the rocker switch to allow the independent switching. This is then bypassed by another jumper from the microswitch (when closed) when the headlights are on to directly provide power to the parking lights. The jumper wires do not come with a new loom. They were originally short blue wires between the rocker and the microswitch, at least on my original Federal 69 S4. I am still using these original jumpers in the context of a new loom elsewhere.

BTW: I think Pharriso's diagram is bit different on the use of the rocker switch. Looks like you have to switch the light rocker switch AND pull the vacuum switch to power the headlights - not have them come on just by the vacuum switch alone. I know my (factory kludged) wiring is correct - but maybe it got changed for later S4/Sprints making you pull the vacuum switch AND turn on the light switch to get the headlights to work? One advantage of Pharriso's approach is that you could raise the lights (release vacuum) but not have the lights switch on - say to clean them. But, it does take two actions to get headlights on, I believe.

Hello JAS,
IMO instead of spending hours to find out what is what (and conclude that it is messed up) I would go and buy a new wiring harness.
Old cables can be a risk, finding melted cables is a bad indicator and in an Elan an electrical problem can generate desaster.
It is also a good lesson, you get into the internal and find out how all is (or should be) connected. A good point for a start over. Not changing will make you always doubt if it is a faulty item or a faulty/broken cable. With new hardness you know it is not the cable itself. Maybe connector or bad earth, but that is far easier to check.

Here's the thread I put together on the federal fail-safe headlight wiring - http://www.lotuselan.net/forums/lotus-electrical-f38/late-federal-fail-safe-headlight-wiring-t30133.html

p.s. It's not my wiring, it was clugged by Lotus themselves!! All I did was document it.

Thank you all for your help!

I am considering a new wiring loom as I have a new dash to replace the old one and will need to take everything apart to do that anyway. I have heard that the wiring looms come in for RHD cars. Is it possible to get one specifically for a LHD?

Jay Supnick

Jay,

I second the advice from gherit, the wiring on my S4 was similar to your description. The more I investigated the worse it was. I replaced the loom. I can't help with the comment about right hand drive looms being the only available type.

Richard Hawkins

My original wiring loom behind the dash also had some alarming melting of insulation. Somehow, I avoided a major catastrophe for the last 4+ decades

By all means opt for new harnesses. As I noted before, most of the looms appear to originate with Autosparks (UK) whether you buy them from UK or US vendors.

When I originally opted to purchase directly from Autosparks they indicated that there were two variants for my S4 (LHD and RHD). Unfortunately, Autosparks had a long lead time to supply them. So I contacted Paul Matty who had them in stock, at a reasonable price. After a bit of discussion about LHD vs RHD versions PM assured me they use the same harness regardless. You just "flip it over" to accommodate a LHD car. Thus, I ordered through them.

I didn't encounter any problems with the Matty supplied harnesses for a LHD. I used the front and dash harnesses - didn't bother with the rear as it seems quite OK. For the dash harness, I did just "flip it over". The wire lengths were fine. I do wonder why Autosparks does draw a distinction between RHD and LHD. Maybe some optimization of wire lengths?

With the harnesses, there was more of an issue resolving the vagaries of the Federal wiring that differ from the wiring diagrams and non-US cars. One really needs to sort through everything, I believe, and understand the wiring, rather than just a "plug and play" exercise. In that process, adding fuses and relays becomes a logical and readily accomplished improvement. Especially with the information available here on the Forum.

Probably the only downside to flipping the harness is that color is off on the turn signals - it should be green/red for left-hand indicators and and green/white for red. A small price to pay!

I'm building my wiring from scratch but I've got a good amount of non-standard things added and am not worried about originality - and the S2 harness is much simpler than a Sprint one!

One last note; the horn may be a special case; you should have a little ground strap straddling the u-joint between the steering column and the rack, otherwise the column isn't grounded. My car doesn't have that and spent decades with a ground wire hose-clamped to the steering column, which would break every few years. I am planning on a fitting a new all-metal u-joint soon which should resolve that once and for all with no need for a ground strap.