Lotus Elan

Electrical jam

PostPost by: spridget » Thu Jun 16, 2011 2:25 pm

Hi

Well, my early +2 (50/0302) had been converted from dynamo to alternator.
But electrical auxiliaries seem to be under powered, light is very poor and raise with acceleration. At idle, the red light is often on.
The RB106 control box is still there but I think is just use to connect wires. So I wonder what to do ! May be the alternator has to be change or at least the internal regulator.
If I decide to change the alternator, what is the best to fit ? I often see on ebay some more powerful which give 70 amp, is it necessary ?

As you can see my electrical knowledge is not really better than my English, so I need your advices !

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PostPost by: Jason1 » Thu Jun 16, 2011 4:46 pm

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PostPost by: spridget » Thu Jun 16, 2011 8:31 pm

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PostPost by: Galwaylotus » Thu Jun 16, 2011 8:35 pm

Unless you have additional loads on the circutry, the problam may well be poor connections or poor earths. If the loads are standard a 45A alternator should be more than adequate. :wink:
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PostPost by: Jason1 » Thu Jun 16, 2011 8:53 pm

So what about that one ?


They all look good. I think I would go for the highest amperage alternator you can find as you say you are having problems with the standard one? 70 Amp one is pretty big.
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PostPost by: Galwaylotus » Thu Jun 16, 2011 9:15 pm

Jason1 wrote:
So what about that one ?


They all look good. I think I would go for the highest amperage alternator you can find as you say you are having problems with the standard one? 70 Amp one is pretty big.

Yeah, 70A is big - too big if you don't have the electrical loads to require it. If you have bad connections or bad earths a larger alternator won't solve your problem :shock: The alternator should be sized based on the electrical loads, e.g, 2 x 55watt headlamps = 110 watts. 110W/12v = 9.2A and so on. Add all the loads together then chose an alternator based on that sum. Even that will be oversized because you don't run all loads all the time (headlamps, brake lights, wipers, indicators, radio, heater, etc. etc. etc.) If the car is basically stock, determine what the output of original charging system was and you shouldn't need a lot more unless additional loads have been added to the car. :wink:
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PostPost by: spridget » Thu Jun 16, 2011 9:20 pm

So what is the right amperage for a standard +2 without any additional load ? 45A ?
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PostPost by: Galwaylotus » Thu Jun 16, 2011 9:34 pm

What did the dynamo put out? On the Elan it was a 22A Lucas unit. It was marginal at best and only gives full output when the engine is revving significantly, i.e. not very much at idle. An alternator provides better low speed charging and most alternators available today start at 35-45A. As stated earlier, unless you have significant additional electrical loads, that should be more than adequate. An alternator will only output the amount of current needed to balance the load and charge the battery. An overly large output won't be used. If you are experiencing dimming lights, etc, it's likely you have bad connections or abad earths. Changing the alternator in that case won't help.
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PostPost by: spridget » Fri Jun 17, 2011 6:44 am

OK, thanks again, so I think I have to check first connections and earths.
And what about the battery ?
Even if there is trouble with charging system, a full charged battery is suppose to
Give all the needed power at least for a while ?
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PostPost by: Higs » Fri Jun 17, 2011 7:59 am

Two things to take into account:

If the red light is on at idle then this might be because the alternator is running too slow. This often happened because the person converting from a dynamo used the same pulley - and the dynamo pulley is designed to run the dynamo slower that an alternator. The dynamo pulley is about 80mm diameter and the alternator one should be about 60mm. Worth a check.

Second point is that if you are thinking of putting a larger alternator on then you must increase the size of the wiring to correspond with this. Particularly the main wire coming from the alternator and going through the ammeter and going to the starter solenoid and on to the battery. Even if you do not have lots of new electrical goodies on the car, when the battery is low and need juice from the alternator to recharge, a large alternator will put, for example, 70 amps through wiring that was designed for 30. A lot of Elans have been lost to fires so please do not add yours to the list.

I would suggest that 45 amp alternator would be fine.

Hope this helps.

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PostPost by: spridget » Fri Jun 17, 2011 11:23 am

Hi Richard

Thanks for this very wise reply. To be honest I don?t even know the output of the one currently fitted on the car
The pulley is a good question, I?ll check

You?re right it?s probably a good thing to keep a reasonable output power
In fact I was first suspecting the internal regulator not really the alternator himself because the battery seems to be always charged despite light on at idle

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PostPost by: kstrutt11 » Fri Jun 17, 2011 12:54 pm

I've used my car all year round with a 17acr and no problems so you should not really need a higher output alternator

I'd also double check that the control box has been taken out of the cirrcuit, if it's still internally connected it would play havoc with your charging.

In simple terms all the large wires should be connected directly to each other and the 2 small ones should be connected to each other, for a quick trial you can use the crimp connectors daisy chained together to make a simple harness to replace the control box.

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PostPost by: gerrym » Fri Jun 17, 2011 1:52 pm

Condition of connections and resulting voltage drops cannot be reliably detected by visual inspection.

As a minimum, remake all connections and remove corrosion etc. Otherwise, have the car at a fast idle with a partially discharged battery and measure voltages along the line (eg, directly at alternator output, solenoid connection, etc so as to find any problem areas. If you want to be thorough, use a low-ohm meter (you will need to make one or hire one because thay are expensive) on each cable and joint.

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PostPost by: Frank Howard » Fri Jun 17, 2011 6:07 pm

spridget wrote:light is very poor and raise with acceleration.

Franck,

Unless you've converted to electric motors to raise the headlight pods, the speed of them raising has nothing to do with your electrical system as they are vacuum operated. It is nearly impossible to find an alternator that puts out less than 35 amps which is more than adequate for an Elan and quite an improvement over the original 22 amp generator that came with the car. I tend to agree with the rest of the group as I believe that most likely, your problem lies elsewhere.

In the states, one can take their alternator to practically any auto parts store and they will test it for free. I would try that first, even if you have to pay for it. Best of luck.
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PostPost by: Galwaylotus » Fri Jun 17, 2011 6:14 pm

Frank Howard wrote:
spridget wrote:light is very poor and raise with acceleration.

Franck,

Unless you've converted to electric motors to raise the headlight pods, the speed of them raising has nothing to do with your electrical system as they are vacuum operated. It is nearly impossible to find an alternator that puts out less than 35 amps which is more than adequate for an Elan and quite an improvement over the original 22 amp generator that came with the car. I tend to agree with the rest of the group as I believe that most likely, your problem lies elsewhere.

In the states, one can take their alternator to practically any auto parts store and they will test it for free. I would try that first, even if you have to pay for it. Best of luck.


I had interpreted Franck's comment as the intensity of the light raising rather than the headlamp pods raising. :?
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