Lotus Elan

Wiring behind dash Elan S4

PostPost by: Watcombe » Fri Oct 24, 2014 6:14 pm

I need to get a good look at the wiring behind the dash on my Elan. Live wires to Ignition switch have been repaired following complete electrical failure, but rev counter all over the place, flickering interior light and occasional engine misfiring makes me think there's more problems. I'm too old to limbo dance under there, so if I remove dash screws and trim underneath, will it come forward enough to have a look & repair as necessary?
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PostPost by: Panda » Fri Oct 24, 2014 8:11 pm

Hi,
You will also have to disconnect speedo cable, and possibly heater and choke cables, to get it back far enough to get one or two skinny fingers in there. But at least it will give you a better view of the wiring. Removal of the tacho also helps
Alan P.
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PostPost by: patrics » Fri Oct 24, 2014 9:39 pm

Just my opinion but you need to drop the column, disconnect oil pressure etc and lay the dash flat
You really need to see what's going on - not easy

Regards
Steve
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PostPost by: elanner » Sat Oct 25, 2014 1:58 pm

I'm with Alan and Steve. Getting the steering column out, and the oil and speedo disconnected, ensures that there is some Limbo dancing in your future anyway! Once you get everything disconnected the dashboard isn't going to fold back far because the glove box will foul the crashpad. So you'll need to take the gear lever out so that you can pull the dash directly backwards, until the glovebox clears the crash panel, and then fold it down. At which point you'll be deep into mission creep territory - washers, wipers, heater, hoses. Ugh.....

Some Limbo dancing might be the better option. Turn the music up! :-)

Nick
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PostPost by: Watcombe » Wed Oct 29, 2014 5:28 pm

Thanks for all replies. Still groping about underneath, and can see some previous owner has done a pretty good job rewiring not too long ago. But I'm now aware of a pattern with the tacho. With the ignition on, engine off, if you hit any other switch (lights, window winders etc) the tacho needle goes hard over to the stop and stays there. As soon as you switch off it goes back. And it's erratic during driving. Tacho faulty? And am I right in assuming it takes its signals from the coil rather than the alternator?
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PostPost by: rgh0 » Thu Oct 30, 2014 6:47 am

If its the original current sensing tacho it senses pulses in the power supply from the ignition switch to the coil. This runs through a loop in the tacho ( white wire in and out) but has no direct electrical connection it as it is a induction coil pickup. The tacho also has a power supply and earth connection for its electronics. Based on its behaviour I suspect that potentially there is a problem with the power or earth connection behind the dash in some way upsetting the tacho electronics when some other device is switched on.

cheers
Rohan
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PostPost by: Watcombe » Mon Nov 10, 2014 5:24 pm

Problems solved. Wire nearly adrift on ignition switch, (piggyback connector broken) and loose earth on light circuit. What a beast to get to. Defeated, I took car to brilliant local garage, who pulled dash forward and got to problems, with only minor complaints about accessibility! Great to still have guys like that around.

Thanks for helpful posts everyone.
PS The back of the ignition switch is soooo close to the (metal) heater box it's definitely a worry.
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