Lotus Elan

Low Reading Instruments

PostPost by: Matt Elan » Sat Apr 13, 2019 2:52 pm

A quick question - my Plus 2 instruments are reading low; while the volt meter has done so from when I gotthe car, the others (fuel, oil pressure, coolant temp) are now showing the same symptoms. I would assume its one of the following things - the ballast resistor is breaking down (or its connections are corroded), there's a dodgy power supply, or the dash earth to the chassis is bad. Anything else the board can suggest?
Possibly (well probably) connected with this is the indicators are not working, and the interior lights go on and off when I move the steering column up and down. Its got a late column with late Triumph stalks (with teh horn button on the stalk).
I'll be diving into the interior tomorrow so if anyone has any pointers I'd be grateful!
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PostPost by: mikealdren » Sat Apr 13, 2019 4:10 pm

The gauges (less the volt meter) are fed via a voltage regulator, that may be failing or even missing. If it is, fit a modern solid state replacement.
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PostPost by: Matt Elan » Sun Apr 14, 2019 1:43 pm

Hi Mike - thanks for that - I realise that I meant voltage regulator when I said ballast resistor.....

Just pulled the under dash trim, and am checking through things before I pull the dash - which I want to do to replace the voltmeter for a better one. The hand brake warning light switch has lost a spade so ordered a new one - the one in place has already been bodged by soldering on a wire which has broken off. I've got power to the indicator switch, but still no indicators. And there is a lovely row of 'chocolate block' connectors in the boot loom which will have to go.

Why do people bodge electrics of all things - especially in a glass fibre car.......
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PostPost by: alan.barker » Sun Apr 14, 2019 4:21 pm

Sorry but it's a Voltage Stabiliser
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PostPost by: mikealdren » Sun Apr 14, 2019 5:44 pm

alan.barker wrote:Sorry but it's a Voltage Stabiliser
Alan

Interesting point Alan, that's certainly what Lotus call it in the manual. What it does is provide a stable (regulated?) 10V supply from the power supply provided by the alternator/dynamo/battery.
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PostPost by: mbell » Sun Apr 14, 2019 6:02 pm

The original/standard one provides an average of 10v by switching on and off the 12v supply which it's good enough for the gauges. A modern one provides a regulated constant 10v.

There is only a few gauges that need the 10v supply so if issue isn't confined to those I'd be looking elsewhere, e.g. dash ground.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: alan.barker » Mon Apr 15, 2019 6:08 am

The voltage stabiliser should be screwed to the back of the metal body of the Tacho or Speedo. This provides the earth and ensures they are in a vertical position.
The original Voltage Stabilisers needed to be vertical. A small reminder that the ""I" terminal is Instruments and "B" terminal is Battery
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PostPost by: Matt Elan » Wed May 29, 2019 4:23 pm

An Update.....

My mate Dave and I had a lovely time trying to diagnose the myriad of electrical problems, and eventually decided to go back to basics. So we pulled the fuse box, which was a non standard four fuse item made in Holland we believe, which had a pair of multi-block connectors going in the top, and another pair taking the wires inside to the dash and elsewhere.
We mapped the input connections to the fuse and out to the output plugs, noting the wire colours, which fuses they were served by and the various common terminals. We then cleaned the fuse box connectors, plug terminals and the plugs themselves, and then checked the ignition switch as the first stage of delving behind the dash.
Putting the fuse box back in temporarily after cleaning sorted most of the issues - I had a working tach, engine temp and oil pressure gauge as well as operating indicators. And the new voltmeter was also working normally. Of course when I took all the plugs out and fixed the fuse box in permanently some issues returned, but at least I know just to sort out the plug/fusebox interface and it'll all be fine. So now its just sort the minor issues, bolt the dash back in and then put the million bits of interior trim that had to come out back in and I'll be able to take it out and discover the next issue....
Oh, and I need to get the fuel gauge working with the new sender unit in the shiny new alloy fuel tank. Which, by the way with a couple of gallons in it doesn't smell of petrol any more so that's another win. Thank goodness and onwards and upwards - or sideways and downward!
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