Lotus Elan

poor electrical voltage

PostPost by: elan+2s » Thu Jun 28, 2018 11:49 am

Hello everybody,

I have a problem in the electrical system of my ELAN + 2. When I am driving with no lights on during the day, the temperature gauge and fuel gauge are working normally. As soon as I turn on the lights, the gauges stop working.

When the light is switched on, there seems to be a voltage drop across the electrical system. The instrument lighting is very dark and the overall driving light is also weak. At the number plate illumination arrive with running engine (3000 rpm) only 11.4 V at. The generator charges with 13 V in the electrical system.

For the weak driving light I had an insufficient ground connection in suspicion. I have therefore put a separate ground cable to the headlights. Without success.

The entire cables are quite new. They were newly installed about 5 years ago as part of the restoration.

Do you have an idea where to look for the bug?

Thanks in advance.

Egbert
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PostPost by: wotsisname » Thu Jun 28, 2018 2:14 pm

I am guessing... it sounds like you have misconnected a circuit , possibly wired a relay incorrectly ?...
I think I would try to narrow it down a bit. maybe part disconnect the engine bay loom under the dash and test each half and work from the results of that ?
Good luck - I have installed a new loom (yet to run the car) and will be interested in what you find

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PostPost by: richardcox_lotus » Thu Jun 28, 2018 4:55 pm

Before you go through every connection, have a quick look at the voltage regulator which should be managing the voltage feed to your non working gauges. I believe it will be a small rectangular box, sometimes attached to the back of the speedometer or rev counter.
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PostPost by: Bigbaldybloke » Thu Jun 28, 2018 11:33 pm

Picture of my voltage regulator attached, the dash is upside down in the picture as it?s on the bench and about to have everything transferred to a nice new dashboard. It?s fitted just under the speedo and Rev counter, held on with one wood screw and may or may not have the extra capacitor fitted to get rid of radio interference.
It must be fitted level as detailed in the manual.
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PostPost by: alan.barker » Fri Jun 29, 2018 5:07 am

Sorry but it's a Voltage Stabiliser and not Voltage Regulator.
For me the Voltage Stabiliser in the photo should have an earth wire under the fixing screw to the dash board.
Without the earth the supply will not be stabilised to 10v.
On some cars they are attached to the metal Speedo body which in effect earths them :wink:
The modern replacements don't need to be fitted vertical either which the original did.
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PostPost by: oldelanman » Fri Jun 29, 2018 6:42 am

alan.barker wrote:Sorry but it's a Voltage Stabiliser and not Voltage Regulator.
For me the Voltage Stabiliser in the photo should have an earth wire under the fixing screw to the dash board.
Without the earth the supply will not be stabilised to 10v.
On some cars they are attached to the metal Speedo body which in effect earths them :wink:
The modern replacements don't need to be fitted vertical either which the original did.
Alan


I believe there are two types. Mine is the same as the one pictured and has three terminals - Battery, Instruments & Earth - it does not require the case to be earthed. The other type with only two terminals - Battery & Instruments - does need the case to be earthed as you rightly say.
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PostPost by: alan.barker » Fri Jun 29, 2018 6:59 am

Well that's new to me, never too old to learn. :wink:
The 4 different Lotuses i have owned have only had the Voltage Stabiliser that needed an earth wire under the fixing screw.
The replacement ones with the printed circuit seem more reliable.

You can also replace with an adjustable Voltage Stabiliser so you can adjust in place to exactly 10v
Alan
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PostPost by: nmauduit » Fri Jun 29, 2018 7:29 am

elan+2s wrote:
When the light is switched on, there seems to be a voltage drop across the electrical system. The instrument lighting is very dark and the overall driving light is also weak. At the number plate illumination arrive with running engine (3000 rpm) only 11.4 V at. The generator charges with 13 V in the electrical system.



if the voltage drop under load is general (like it seems to be here, since the rear of the car is concerned) it could be a battery connection oxidized : that causes a increased contact resistance, and when current demand increases the voltage drop across it increases. On my S4 the culprit was the earth connection in the trunk.
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PostPost by: elan+2s » Fri Jun 29, 2018 8:40 am

Thank you for your many responses.

I think I can rule out the voltage stabilizer. The stabilizer (exchanged 2 years ago) is only responsible for supplying the two instruments with a constant 10V. If this were the fault, I would only have a problem with the ads. Instrument lighting, lighting ect must work without restriction. I denek that the voltage that arrives at the voltage stabilizer under load is less than 10V. That would also explain the problems of instrument lighting.

I'll check from the relay on where the voltage breaks down. But it will take some time until I can report it. I am currently working on another project. (paint the enginebay of my BMW E9 :-))

Regards Egbert
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PostPost by: nigelrbfurness » Sat Jun 30, 2018 8:12 pm

Check and clean all your earth returns, sounds like your lights are returning via circuitry other than their normal earth path. Current to the lights is not fed through the voltage stabiliser and if you're running an alternator, the regulator is built in.

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