Lotus Elan

Installing Amp Meter properly

PostPost by: loueelotus » Mon Feb 27, 2017 4:27 am

Hi,
I need a little information on the installation of an amp meter on my Elan S2 65.. I have read the different ways to do it but maybe someone can explain which is the best and safest way to do it in regards to electrical issues that can develop and fires.

Regards,
Lou
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PostPost by: 65sunbeam » Mon Feb 27, 2017 11:50 am

The easy answer is-install a voltmeter instead. Smiths made a very nice voltmeter back in the day-and is available as a repro now- that you can install and not worry about all of the car's electrical system amperage running through your amp meter. Eric
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PostPost by: alan.barker » Mon Feb 27, 2017 12:00 pm

100% imho also it's a safer bet to fit a Voltmeter
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PostPost by: Elanman99 » Mon Feb 27, 2017 2:55 pm

There isn't a way of installing an Ammeter 'properly' in the sense that it was never an original fitment. From an electrical and installation point of view a Voltmeter is much easier but more to the point is much better indicator of the state of the vehicle electrics.

I am not an originality freak so adding another gauge to the dash would not bother me but some people would regard cutting a 2" hole in the dash as sacrilege.

The simplest way to monitor the electrics is to purchase one of the cheap digital voltmeters that fit into the cigar lighter socket.

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PostPost by: YellowS4DHC » Mon Feb 27, 2017 11:54 pm

Have to concur with the posts regarding the liability of having hot, unfused wires at the back of the amp gauge. If it were me, I'd use a volt meter that had the same look as the other gauges, plus I'd install a battery disconnect switch inside the car. It's helpful as a theft deterrent and you can cut power quickly if you smell insulation burning. :)

If you do decide to use an amp gauge, be sure to use the correct gauge of wire with insulated terminals, make sure all connections are low resistance, and ensure that nothing can short against any nearby ground. Especially make sure the female spade connectors at the gauge fit very snug and won't come loose.

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PostPost by: elanner » Tue Feb 28, 2017 12:49 am

Unless you want to watch the current while driving, why not use a simple inductive ammeter clipped on to the cable from the battery in the trunk? Err, or behind the seats in an S2?

For examples, see:
http://www.stuttgartperformanceengineer ... mater.html
http://www.autoelectricsupplies.co.uk/p ... ategory/88

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PostPost by: Craven » Tue Feb 28, 2017 1:10 am

If comments in this thread has you worried about your car bursting into flames but you really want to measure current then there are plenty of this type, Non contact hall effect ammeters, around
http://www.cheaprvliving.com/forums/Thr ... ct-ammeter
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PostPost by: billwill » Tue Feb 28, 2017 2:27 am

I differ from an above opinion because I think an ammeter is a much better indicator for electric problems.

With an ammeter you can see if there are any devices taking excessive current, or nil current for a blown bulb etc. You can see if the dynamo/alternator is charging the battery.

A voltmeter basically only tells you if the battery is being charged OK.

As to where to fit it, you do not want it in the thick starter-motor circuit, because that would need a very high current ammeter, so the logical place to fit it electrically is in the thick(ish) brown wire that runs from the solenoid to power the ignition circuits and the fuses. However I don't have a circuit diagram to hand to see if any wires (such as that from the alternator) bypass that brown wire.
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PostPost by: Craven » Tue Feb 28, 2017 12:13 pm

Horn current not normally included.
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PostPost by: EPA » Tue Feb 28, 2017 2:34 pm

I agree that an ammeter provides more information but the viability of fitting one relies very much on the output of the alternator. The higher the output the more potential there is for undesirable problems with fitting the meter in the dashboard. The ones that use a clip on or feed through pick up are much saver but can you get one of these that matches the look of the original ?
I swapped my ammeter for a voltmeter when I fitted an alternator as I think the advantages of the ammeter are outweighed by the potential risk of feeding the higher currents behind the dashboard.

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PostPost by: denicholls2 » Tue Feb 28, 2017 3:01 pm

To the point of the dangers of period ammeters, I would note that the contemporary Europa had an ammeter as original fitment. I would recommend using that wiring diagram as a starting point, but the basic idea is "everything but horn and starter".

The ammeter is good for finding shorts and identifying issues with the voltage regulator, also potentially for right-sizing relays for the larger current draws (headlights) if a relay wasn't fitted originally (in Europas, all of the power goes through the switches as stock, which is not a great idea with a Lucas dipswitch).

Voltmeters are nice too, they will tell you if you are overcharging your battery or if the battery has a weak cell.

My opinion would be that for the health of your electrical system and the things that might be torched by it, the largest risk is an oversized alternator because it can typically double the current supply of the original. Provided the alternator can keep up with the level current demand of the electrics, there's really no reason to install a big one. But many people do. Air conditioned cars or cars with mega-power amplifiers for the audio system are potential exceptions (and sources of high-load connections).
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PostPost by: Chancer » Tue Feb 28, 2017 3:28 pm

What is the rationale behind not passing the horn current through the ammeter? Does it make the needle oscillate?

I always thought that an ammeter broke the circuit of the main (usually) Brown wire from the battery or starter solenoid (not the main battery lead) so was unfused and passed all current except the starter motor.

I fitted an ammeter to my Kevmobile (Viva :( ) when I was a young inexperienced and overconfident hoon, the result was predictable to everyone but myself :( - I have shied away from ammeters ever since
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PostPost by: stugilmour » Tue Feb 28, 2017 4:32 pm

Similar to the Europa, the early Plus 2 came stock with an ammeter. Lotus switched to a voltmeter with the introduction of alternators. The Plus 2 Workshop Manual actually has a section detailing how to retrofit a voltmeter if upgrading a car to an alternator, which I scanned below.

As described in several of the earlier posts, the voltmeter wiring is easy. One terminal to ground, and the other terminal to a suitable "Hot in Run or Start, Unfused" terminal. The 12v voltage stabilizer input terminal (typically mounted to the tachometer) is used in several of the Plus 2 diagrams. The wire gauge can be very light as the circuit sees very little current. With a bit of luck you may not need to remove the dash to install and wire the voltmeter.

If you are looking for a "period correct" voltmeter, it is sometimes referred to as a "Smiths Battery Condition Indicator" or similar. I bought one on eBay UK that was similar to the gauge shown in the Plus 2 Workshop Manual. Strangely, the bezel cover over the needle was different; I switched the piece from my existing ammeter so the gauges match better.

Here is a listing for the period correct gauge (at least as shown in the Plus 2 WSM). Note the rounded shape of the needle cover and the green and red colours on the gauge face.

Batterey Condition Indicator.jpg and
This is the 'period corect' Battery Condition Indicator shown in thew Plus 2 WSM.


http://www.ebay.co.uk/itm/classic-smith ... SwjDZYd-Wa


This listing shows a needle cover with the angled sides. The gauge face is slightly different, with just red on this one. Looking around eBay, it appears gauges similar to this one are available new.

Voltmeter.jpg and
This is the voltmeter version. The needle cover matches the other gauges better. Looks like this one is available as a new gauge.


http://www.ebay.co.uk/itm/Smiths-Voltme ... SwCU1YtG5p

For my 1969 Federal Plus 2, the stock ammeter was wired as follows:

  • Brown / White wire, size 44/0.010, to the RB340 voltage regulator (the terminal has another Brown/White attached). The wiring diagram is not very clear, but appears to be the A terminal?
  • Brown wire, size 44/0.012, to the main solenoid terminal (where the large black cable to the battery is attached).

I am not familiar with the S2 wiring layout, but the first thing to check is if the large gauge wire from the control box / voltage regulator is mounted to the dashboard or to the engine bay firewall. If it presently runs across the firewall, installing the ammeter becomes more difficult and problematic as the wire has to be relocated. If the wire runs across the dash, it still becomes a dash out job.

As mentioned above, the general ammeter wiring configuration places a "Hot at All Times, Unfused" wire and ring connectors next to the wooden dash. Typically you will want additional connectors in the circuit to allow dash removal. All of these spots provide a risk of fire from a short circuit.

HTH

Stu
Attachments
Plus 2 Battery Indication Indicator 3.pdf
(245.5 KiB) Downloaded 235 times
Plus 2 Battery Condition Indicator 2.pdf
(225.1 KiB) Downloaded 192 times
Plus 2 Battery Condition Indicator 1.pdf
(205.02 KiB) Downloaded 216 times
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PostPost by: loueelotus » Tue Feb 28, 2017 6:14 pm

Thank you all for the wealth of information from all of you.. I will study it all and decide though I think I will go for the ammeter.. I had a ammeter in my early Elan +2 which was standard and I once had trouble with something discharging on the circuit at that time I brought it to my mechanic and fixed the issue fight away. Now I do my own work.. I am going to try to send a photo of the pre instillation. Excuse the lack of carpeting I am installing new carpets and updating the interior of the Elan. Our winters are so long in Canada that we have a lot of time to play :cry: ..

I have another question. Is there any wire that is better (Brand name) and the best thickness wire? My ammeter reads + - 50 which it will never get to..One of the threads said (which I thank you very much for) Though I have a RB 106/2 regulator Positive ground.
Brown / White wire, size 44/0.010 to the RB340 voltage regulator (the terminal has another Brown/White attached). The wiring diagram is not very clear, but appears to be the A terminal?
Brown wire, size 44/0.012, to the main solenoid terminal (where the large black cable to the battery is attached).
Thanks again for all the info.
Regards,
Lou
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PostPost by: stugilmour » Tue Feb 28, 2017 7:51 pm

Lou, when I rewired my car I used materials from the following two overseas suppliers. I had no issue with either firm. I have filtered the link down to the thin wall cable that I used. The electrical current capability is listed for each size. Note the largest Brown they list is 63 amp, which would be more than adequate.

The various wire colours available in each size can be seen in the drop downs. Note you will probably have to use Brown for both wires, as the largest available Brown / White appears to be 25 amps.

http://www.vehicle-wiring-products.eu/s ... wall-cable

http://www.autoelectricsupplies.co.uk/p ... tegory/114

The reason I typically used these overseas suppliers is they have a wide variety of traced wire colours (in more moderate sizes of course). Both of these suppliers are excellent for the proper crimping tool and connectors you will need.

You could also check out local auto parts or trailer wiring stores in your area, as large gauge Brown should be available. Unfortunately, in North America, the larger wire sizes are more common in Black, Red, and White rather than Brown. For example, Princess Auto only carries Brown in AWG 12, which may be a bit light for your application. Someone else may know better your generator output, and adjust wire size as required.

http://www.princessauto.com/en/detail/1 ... -p8216756e

This chart provides the current rating by the AWG sizes that are more commonly used in North America. AWG 10 is 55 amps, which I think is what you are after?

http://www.powerstream.com/Wire_Size.htm

The wire sizes I posted earlier from the Lotus WSM diagram are different. I can't quite recall the details of the specification, but the first number is the number of strands (44 in this case) and the second number is the strand size (can't remember the unit; someone else may know).

I think the Brown / White is attached to terminal A of the 106 control box; that is how it works on the various Plus 2 diagrams. That said, I have always found the whole control box thing black magic, and prefer the simplicity of a modern alternator. :D

HTH

Stu
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