Lotus Elan

Alternator Wiring Mystery

PostPost by: jbeach » Wed Mar 11, 2015 9:14 pm

Hello All,
I know this is a long shot, but our community has amazing talents, so here goes...

As I explore and sort out the many mysteries of my '69 Federal Elan S4 DHC, I've observed four characteristics I believe may be interrelated:

1. The car runs whether the ignition key (in the dash, not on the column) is in the "on" position (all the way clockwise) or the "Acc" position (all the way counterclockwise);
2. The car tends to "run on" (we call this "dieseling" in my part of the US) after the ignition key is in the "off" (center) position. Because of 4, below, my local mechanic believes this is not true "dieseling", but is ignition-related.;
3. The brown with white stripe (I think it's brown - I'm a little color blind) cable you see connected to the top of the alternator (alternator installed by PO) is "hot" even when the key is in the "off" position; and
4. A test light shows small pulses of electricity going into the coil when the engine is "running on" even though the ignition key is in the "off" position.
Beach Elan Alternator Connections.jpg and


I know, I know, I should put a rubber boot where the hot wire connects to the alternator - I promise it's on my list!

At any rate, do any of you who are gifted in mechanical know-how and the art of deductive reasoning have any advice on what might be going on here? I'll try to answer any additional questions you may have.

Best and many thanks,

John
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PostPost by: mbell » Wed Mar 11, 2015 9:32 pm

jbeach wrote:3. The brown with white stripe (I think it's brown - I'm a little color blind) cable you see connected to the top of the alternator (alternator installed by PO) is "hot" even when the key is in the "off" position; and


It is brown, it is the main Alternator output connection and is directly coupled constant live circuit on the car. So it should so ~12V at all times, no matter what the state of the ignition/engine. So no problem here.

When you say "run on" do you mean it runs for a few seconds and stops or do you mean the engine continues to run as normal? (apart from it should have switched off)
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: jbeach » Thu Mar 12, 2015 2:02 am

Thanks for confirming the brown/white wire should be hot even with the ignition "off." It's a relief to know at least that is correct.

Yes, when I say it runs on with ignition in the off position, I mean it chugs on for a short time. I usually stop the engine by judiciously engaging the clutch.

Best,

John
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PostPost by: rgh0 » Thu Mar 12, 2015 3:01 am

I presume you have Stromberg carbs? They are prone to running on and there are quite a few discussion on this you should be able to find. So the running on may not be related to the ignition question. I am not sure why you still see weak pulses on a test light when the ignition is in the off position and the engine is running on, potentially there is something else connected to same terminal as the ignition circuit and you are getting a back feed from some other source such as the ignition light circuit from the alternator

It sounds like the ignition wire has been connected to the accessory terminal so it is live in both that accessory position and the normal run position of the key. It should be a White wire that runs from the ignition to the Tach and then to the coil if you have the original current sensing tach still.

cheers
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PostPost by: gjz30075 » Thu Mar 12, 2015 8:29 am

John, exactly where on the coil is the test light placed?
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PostPost by: gus » Thu Mar 12, 2015 1:02 pm

Where is the brown/yellow wire connected on the vehicle?

It should go to one side of the ignition light



Do you have an electric fan that might be wired on all the time[they will act as a generator, and cause the car to continue to run after the key is turned off for several seconds]

It is possible the ignition switch is wired improperly, for instance if the ignition is wired to the acc position it will run in both ignition and acc positions
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PostPost by: pharriso » Thu Mar 12, 2015 2:09 pm

That looks like the Ray Dent alternator conversion, I am attaching Ray's installation instructions so you can check your wiring:
AlternatorInstallationInstructions_RDent_Reduced.pdf
(574.22 KiB) Downloaded 445 times


I would check your ignition key wiring is per the manual as well.
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PostPost by: William2 » Thu Mar 12, 2015 5:00 pm

The only comment I would make is that it is not the correct alternator for the car.
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PostPost by: pharriso » Thu Mar 12, 2015 5:11 pm

William2 wrote:The only comment I would make is that it is not the correct alternator for the car.



It's the one that Ray (RDEnterprises) sells in the USA for the Elan as part of a kit.

What do you consider the "Correct" alternator to be?
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PostPost by: jbeach » Thu Mar 12, 2015 6:07 pm

Thanks to you all for your responses and questions. Here are my answers, working down,

Rohan,
Yes, I have the Stromberg carburetors. I've read the threads on those and was left with the final impression run-on is, to some extent, unavoidable with the Strombergs because, unlike the Webers, they do not completely cut off flow when you remove your foot from the accelerator. My local mechanic installed some colder plugs, but it didn't solve the run on and caused them to load up. I quickly installed some hotter plugs and solved the loading up problem.

Greg,
I'm not sure where the test light was connected. This was a few months ago when I picked my car up following a bunch of work. My mechanic had it connected when I arrived, said "look,this is interesting and could have something to do with your run on" and rushed me off to the cashier.

Gus,
All of my alternator wires are connected to the existing (but apparently, now, non-functional) RB106 Control Box. I've checked and they do appear to coincide with Ray's wiring diagram (thanks Phil!). And yes, you read that correctly - my '69 S4 has an RB106, not RB340, control box. Another one of the great mysteries of my Elan.

And yes, I do have an electric fan that's always on!! This is a point of constant irritation, but I haven't had time to either install a thermostatic switch or wire it to a manual switch in the car (likely, the panel light rocker switch). I'll test your (very welcome) "fan as generator" theory this weekend by disconnecting the fan and see whether that improves the run on problem.
Phil, and others:

This weekend I'm going to remove the ignition switch from the dash (I assume I can do that without removing the entire dash panel, but please confirm) and make certain the wiring is correct per the Workshop Manual.

So I have a very busy weekend (I'm also installing a new hydraulic line for the clutch I just received from Pegasus), but hopefully a weekend that results in the resolution of a few problems.

Thanks so much! I'll post my results as soon as I have a few moments.

Best,

John
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PostPost by: Bud English » Thu Mar 12, 2015 7:02 pm

William2 wrote:The only comment I would make is that it is not the correct alternator for the car.

Interesting thread here: lotus-electrical-f38/alternators-t2310.html

I especially like John Clegg's comments. They are applicable here as well.
My '70 +2S came to me from the DPO with the ineffective Bosch version of the Lucas unit that the factory sold as a retrofit kit. If the only "correct" alternator is that one, there are quite a few cars out there with incorrect alternators mounted. ...and as John says, :wink:
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PostPost by: billwill » Thu Mar 12, 2015 8:52 pm

jbeach wrote:

This weekend I'm going to remove the ignition switch from the dash (I assume I can do that without removing the entire dash panel, but please confirm) and make certain the wiring is correct per the Workshop Manual.


John


It isn't easy but it can be done, on my S3 at least. Remember to disconnect your battery in the boot first as you are quite likely to touch contacts to earth or other switches.
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PostPost by: gus » Thu Mar 12, 2015 11:12 pm

"fan as generator" theory

not a theory, my 7 does this as it has no relay and if it is running when the car is shut off, this happens. My +2 used to have no relay, and same thing
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PostPost by: john.p.clegg » Fri Mar 13, 2015 8:53 am

My Plus2 has a thermo switch , a manual overide switch, and a lamp to monitor the fan and when " whizzing along" the lamp glows showing an output from the fan motor.....

John :wink:
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PostPost by: William2 » Fri Mar 13, 2015 11:06 am

I think the correct alternator is an LR17 which has a 35A rating.
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