Lotus Elan and Lotus Elan Plus 2 Forums

Dear Elan Community,

I realize the ultimate answer to my question will be "get an accurate wiring diagram, trace your current ignition wiring, and re-wire to reflect the correct, factory setup." But, I'm hoping some of you electrical whizzes can offer some thoughts and advice that might make diagnosing the problem and implementing the solution a little easier.

The problem is simple to describe - my '69 S4 DHC Federal has the ignition switch on the dash. When the switch is turned one click clockwise from the central "off" position (that is, to "on"), the coil is getting an appropriate electrical current for plugs to fire and Elan to run. When the switch is turned one more click clockwise (to "ignition") the starter is engaged, but the coil loses current. When the ignition switch is turned one click counterclockwise from "off" (to "accessories") the coil continues to receive current, and the car continues to run as if the ignition were in the "on" position.

As a temporary solution, I have wired a micro-switch from the starter solenoid. To start, I push the button to engage the starter while the ignition switch is in the "on" position.

I'm certain the previous owner did some wiring work that somehow involved the ignition wiring, and simply rewired the ignition circuit incorrectly. Now that I'm into the home stretch of my restoration, it's time to remove the micro-switch and correct this wiring issue.

I solicit your thoughts and recommendations, even if they are "get an accurate wiring diagram, trace your current ignition wiring, and re-wire to reflect the correct, factory setup.

Best,

-John

That sounds like the correct wiring for the reduced voltage coil. This has a resistor in the normal feed to the coil in the wire from the ignition switch that comes live on the first position. When turning to the second position to engage the starter there is a second wire from the starter solenoid that supplies the full 12 volts to the coil to give a big spark for easier starting, once you release the key from the start position the coil once again gets fed the reduced voltage as I believe the coil is rated at 9 volts for continuous use. Sounds like you may be missing the wire from the solenoid to the coil. Suggest turning the ignition on and measuring the voltage at the coil, should be around 9v.
Lots of questions on here around the resistor location in the coil feed, some have a resistor on the coil, some seem to have a resistance wire feeding the coil. Several possible explanations, someone may have fitted a 12v coil that doesn?t need the resistor, it may have had electronic ignition in the past which has been removed or just the solenoid to coil wire disconnected or broken. Lots of variations in ignition switch contacts and the way they connect in each position you may have the wrong switch fitted, or the coil connected to the wrong tab on the switch, certainly the ignition should not be powered in the auxiliary position otherwise the coil will overheat and be damaged if left in this position without the engine running. The connection that is live in the auxiliary switch position should only provide power to the radio. How many connection positions on your switch, some have three and other four, I?ve just replaced mine as I couldn?t find the key after 30 years off the road, I ordered the replacement from one of the eBay vendors and it works fine, it?s a genuine Lucas switch. Hope this helps.

Just about to say the same thing about a resistor coil, beaten to it!

Thanks to both of you. What you say makes sense. One other fact (probably the genesis of the problem) is the previous owner installed electronic ignition. It sounds from your explanation that will make a difference.

I've been scouring the website for a good wiring diagram and came across this in a 2006 post:

"Have you seen in the LotusElan.net Library>Technical Tips>Electrical there is an S4 wiring diagram in colour? It has been produced using a CAD tool, but there is also a bmp version. Very useful and a lot more clear than the original."

I've looked at the Library and do not see a section called "Technical Tips." Wondering whether it was removed, or simply shifted somewhere else. I could use a good color wiring diagram.

Best,

-John

Picture of ignition switch wiring attached, there are four contacts although some have multiple connection tabs on them. The one with the large blue and brown/blue connection is the power to the switch, going clockwise from that the two red/green wires are the ignition feed to the coil via the tachometer. The white/red wire goes to the starter solenoid and from there should provide the 12v supply to the coil when starting, the final white wire is just for the radio and is live in all positions except the off position where you can withdraw the key. Note that the photo was taken of my plus 2 dash upside down on the bench!

jbeach wrote:I've been scouring the website for a good wiring diagram and came across this in a 2006 post:

"Have you seen in the LotusElan.net Library>Technical Tips>Electrical there is an S4 wiring diagram in colour? It has been produced using a CAD tool, but there is also a bmp version. Very useful and a lot more clear than the original."

I think you may be looking for this post containing a S4 wiring diagram.
lotus-electrical-f38/wiring-diagram-t29157.html

Looking at the switch logic I would suspect that the ignition coil feed wire (which should be white) has been connected to terminal 4 instead of terminal 2 so it is powered in the AUX and RUN switch positions but not in the CRANK position ... which is I think what you described.

Thanks to all three of you. This is literally the perfect combination of responses - the amazing photo of the actual wiring, a link to the color wiring diagram, and, finally, the message from Oldelanman that, I'm fairly certain from looking at the other materials, nails the actual problem. I love this forum.

I'll tackle this Saturday morning and give everyone an update when I'm (hopefully) done.

-John

I must say I'm impressed!

John, not sure if you have resolved the issue yet.

Does sound like a wiring issue in that accessory setting is incorrectly powering the coil.

Anyway, suggest taking a minute to function test the actual key switch with the wires disconnected. My switch was working correctly in run but not in start. Car would actually start as the starter created enough momentum that the engine would immediately fire when the key was released to the run position. I temporarily fixed it with contact spray, but eventually a new switch was required.

HTH. Agree this forum is excellent and the tips above are terrific.

Stu

Stu, function testing the ignition switch is a good suggestion. Will do.

OK, I?ll admit I got a little sidetracked this weekend and only spent a little time upside down and on my back, peering into that mysterious world behind my dash. It?s fascinating up there, isn?t it?

So I have a couple of questions:

First, will it be possible to remove the ignition switch without unscrewing and pulling out my dash board a few inches? It?s pretty tight in there! Any tips?

Second, what is the sliding switch just above my hood release? It?s actually mounted in the bracket that supports the release handle.

Best,

-John

Can?t help with an S4 but on my plus 2 I changed the switch in situ but did undo the securing screws at the bottom and loosened the top ones to allow me to pull the bottom of the dash back an inch or so to get better access. I?m sure you will, but disconnect the battery first as it?s an unfused live feed to the ignition switch!

jbeach wrote:
Second, what is the sliding switch just above my hood release? It?s actually mounted in the bracket that supports the release handle.
Best,
-John

Hazard switch ?
Does it have 2 green and 1 light green wires connected? .... that would confirm it.