Mobelec ignition system

[Mrozik]

Hi
I have an S4 Elan that has been fitted with a Mobelec ignition system. The ignition part works very well but I can't get the tachometer to react - it is currently activated by a direct line from the coil but it currently just fliggers.
There is a tachometer adaptor but I have no idea of how you wire this into the system.
Any help with this woould be much appreciated.
Thanks
John

[billwill]

Insufficient information:

It all rather depends on what kind of electronic ignition that is.

Some are simple transistor switches,

Some are that but have contactless-sensors.

Some are Capacitor discharge systems.

It's up to you to research & tell us what kind of electronic ignition it is. I tried a quick Google search but the relevant info did not turn up.

[Mrozik]

The only thing I can find is that is that its a "Contactes Ignition Sytem E Series".
Does this help?

[billwill]

The only thing I can find is that is that its a "Contactes Ignition Sytem E Series".
Does this help?

Not really.

There are many topics about electronic ignition on this website, but the seach facility is not particularly good so try using google instead thus:

Use Google to search for [Electronic ignition site:Lotuselan.net]
and then pore through the results.
and
[ tacho site:lotuselan.net]
and then pore through the results.
and
[tachometer site:lotuselan.net]
and then pore through the results.





~~~~~~~~~

Edited to replace the pour spelling of pore

[UAB807F]

If you pull the distributor cap then you can see if the car still has the contact breaker points, a magnetic sensor or an optical blade system. That should give some clue as to what we're dealing with - "points assisted", hall effect (magnet) or an optical sensor system.

With some of the magnetic systems folks have got the tach working by setting up an independent power supply, not from the coil but elsewhere. Other options include adding a circuit board inside the tach from Spyda which converts the old electronics to work with modern systems.

I replaced the internals completely on mine using parts from an aftermarket stand alone rev counter but that was before I'd read about the Spyda option.

Regardless of what ignition you're dealing with, do you know if the tach works with CB points ignition ?

Sadly I've no idea what a tachometer adaptor looks like so can't help you there.

Brian

[Mrozik]

Thanks for the advice.
There are definitely no traditional points there.

As there is a tachometer adaptor already present what I think I need is a guide on how to reconnect it to the ignition system as I’m sure this will solve the problem.
Can any one help with that?

Many thanks
John

[billwill]

Thanks for the advice.
There are definitely no traditional points there.

As there is a tachometer adaptor already present what I think I need is a guide on how to reconnect it to the ignition system as I’m sure this will solve the problem.
Can any one help with that?

Many thanks
John

But you are not giving us any clues as to what that adaptor is? It could be almost anything so no wonder we can't advise you.

Try reading the pages of the Spyda website. They are AFAIK the main convertors of the Smith's tachometer & see if that give you a clue:
https://spiyda.com/smiths-rvi-rvc-conversion-board.html

For Lotus cars there are two main types of tachometer, the original is current-sensing it measures the pulse of current in the white wire that leads from the ignition switch to the ignition coli. the connection on the instrument basically consists of two turns of the white wire around a metal strip bolted on the back surrface of the instrument. Later versions of that tachometer have the two turns inside the instrument so the white wire has a male & female bullet connetctor which can 'break' the wire and it is then plugged into two single-pin sockets, one male, one female, to carry the current through to the internal loop. Quite often this type of tachometer does not work well with electronic ignition.

This is the circuit of the first type of tachometer:


For the second main type of tachometer, it is built or converted to sense voltage pulses instead of current pulses. It gets its signal from the other end of the ignition coil as a single extra wire which comes back from the coil to the tacho. It connects to a single terminal on the back of the tacho. Sometimes the voltage signal from the coil is too big or too 'noisy' to suit the tacho, so there may be an adaptor, which might consist (in the simplest case) of two resistors and a smoothing capacitor. If so one wire would go to the 'ignition coil' another wire would go to the signal input of the tachometer and a third wire (or the case of the adaptor) would need to be connected to ground. Because the magnitudes of the coil signal are not really known, the two resistors might be replaced by a variable resistor (potentiometer) where the sliding contact is used to feed the instrument and the ends of the variable resistor are connected respectively to the ignition coil and to ground.

Some Electronic ignition boxes have an output point for signalling to the tachometer, if so, use that, instead of connecting to the 'bottom' end of the coil.


I regret, I do not have any handy diagrams of connections of the second kind of tacometer circuit.

[Mrozik]

Many thanks for the very useful info.

I’ll take a photo of the adapter as soon as I’m back in the uk at the end of the month as I left for my hols yesterday.

One of the problems is that whoever installed the system used the same colour wire for all the adapter connections!

Cheers

[Mrozik]

Hello

Attached a couple of photos of the fitted adaptor - hope this helps determine the required connections

Many thanks
John

[billwill]

That's not really any help, to anyone other than someone who has used that particular system.

To be of any real help you would need to open the adaptor and photograph the components inside.

The presence of the adjusting screw indicates that there is probably a potentiometer inside, but that's all it really tells us.

An Image search on Google did not reveal any similar device, only lots of pictures of boxes that could not possibly be related.

Do you have a multi-meter, or are you expecting miracles? If you haven't got one then buy one they are inexpensive on places like Amazon nowadays, and you won't get far on auto circuits without one.

With a meter you should quickly be able to determine which wire is the ground because it will be connected directly to the casing. I presume there will then be two other wires. One would go to the tachometer signal pin and the other should go to the bottom end of the ignition coil. If it is just the simple circuit that I described earlier, it won't do any harm if you try the two alternatives, i.e try one combination, if that doesn't work try the other..

The basic circuit is like this:

Basic circuit with tachomether adaptor

From this you should be able to work out what to do!

[alanr]

Doing a bit of searching on the web reveals that Mobelec went out of business around 1979!...So perhaps it is time now to say goodbye to it?
However having said the above I have found on the web an opened page of the Mobelec instruction manual showing how the Tachometer is wired. Perhaps you can enlarge or use a magnifying glass to read it?

Whilst the system in the pic does not have a separate adaptor hopefully you can sort the wiring from this.

Alan

[Mrozik]

Many thanks Alan - I'm grateful for any clues!

And many thanks BillWill for the diagrammes, I'll get the multimeter out and do as you suggest.

Many thanks
John

[Craven]

Mrozik John
If you right click on the image provided by Alan and select ‘Open link in new window’ you will be able to see all the information you need. Adaptor unit should not be required with a Current Impulse Tach fitted in a S4 elan.

[Mrozik]

For everyones information, in spite of all the help, I just couldn't get the mebelec system to work with the tacho so ended up changing the whole system to an upto date contactless sytem supplied by Ignition car parts Ltd. Perfect now!

[mark030358]

amazing how some replies are really helpful while others are...................