Lotus Elan and Lotus Elan Plus 2 Forums

Asking for suggestions before I conclude I've been sold a dud alternator. Over the weekend I fitted a Dynamator (alternator) to replace my Dynamo, pretty simple swap in with the same two electrical connections on the back. I switched my +2 to negative earth a few years back.

Wiring instructions advise patching the field connection straight through to the warning light and the main connection direct to the + terminal on the solenoid.

Switch on ignition, battery light glows. Start engine, light stays on. Take it out for a quick blast, revving to over 4k, battery light stays stubbornly on. Alternator shows drain only (which is fine since I've bypassed it and connected directly @ solenoid), but I have a voltmeter that confirms no charge (~12v running, voltage drop with headlights on, voltage steady regardless of engine speed etc).

Used a hand voltmeter to confirm that there was 0v at the alternator post with engine running. I had exactly the same problem with the dynamo, though it did show a little bit of voltage (not much)

I don't beleive the belt is slipping, I'm using a (loose) toothed belt and the alternator pulley seems to spin up properly. If it was slipping a bit I'd expect to see some kind of voltage swings in use?

Engine earth is good enough to start the car without issue.

I'm stumped.

Hi

With a dynamo you would have had an external control box. A conventional alternator does not need this. So the ignition lamp should connect one end to the ignition (+12V) and the other to the field ( smaller) terminal on the alternator. It may be that you have to bypass the cut out feature in the dynamo control box. DONT run an alternator with no load connected. Under some conditions it can damage the rectifiers that are built into it.

I am not familiar with the dynamator is this a trade name for a alternator replacement for a dynamo?

hope this helps best of luck

bob

Bob,

Happy that wiring for lamp is good, on the basis that it was good for generator wired through the regulator, and is lighting up with Alternator wired to bypass the regulator. Lamp lights, but won't go out. If I disconnect at alternator or at join (where I bypassed the regulator) the lamp will not light.

Reading the archives I se a number of people mention that their alt did not cut in until a relatively high engine speed, but would then remain in as revs fell. Something about exciting the "whotsits".

Since posting, I?m wondering whether I could have belt slippage such that my alt pulley doesn?t get over (eg) 800 rpm and the alt therefore never cuts in?

Dynamator installation was discussed recently, read through this topic, which included a link to the relevant circuit diagram, I recall.

lotus-electrical-f38/dynamator-conversion-t28679.html



As I understand it, the F terminal is not really a FIELD connection any more, but a connection to a point whose DC voltage rises as the alternator generates volts. Since you connect it to the car battery via the ign light bulb, when the engine is slow or not running, current flows from the battery through the bulb to the F terminal and it lights up. When the engine is running the voltage climbs opposing the volts from the battery until eventually BOTH sides of the ign bulb are at 12 volts (approx) relative to earth so there is no flow through the bulb and it ceases to glow.


Your symptoms could be caused by a bad earth connection between the dynamotor and the engine body. But I think, the most likely cause is that you didn't move the wire to the A terminal of the old dynamo control box.

Thanks Bill, I've wired the warning light as per your diagram but wired the alternator output directly to the battery positive terminal on the solenoid (to avoid any possible issues related to the regulator.

I've considered bad earth (via the block), but I'm thinking it must be OK because the starter motor (also earthed via the block) works fine.

Hi again

Now have seen info could it be that the connections on regulator box A and A1 which should be a tapping on the series coil and the resistance A to A1 should be very low. I have know regulator boxes to corrode so that the A to A1 connections goes open circuit If there is no voltage on your A1 terminal that may be the problem.

However you said you tried the Dynamater output to the solenoid +ve ( I assume it is the live side? not the starter motor side -- easy mistake perhaps ) If so there should at least be +12V at the Dynamater main output terminal whether it works or not. The volts should be there with the engine and ignition both off. I dont know what the Dynamator does inside but it may be that with no volts at the main terminal from the battery that it may not work.

Is a Dynalite the same system as a Dynamater?

Hope this helps interested to know what you finally find

best of luck

Bob

Losing heart now, think the alternator is a dud. When I got home, I tightened the belt a bit, and managed to get the warning light to go out when I revved (goes out entirely or sometimes dims). System voltage still at battery level though, no charging current measurable at the solenoid (well may +1v if I rev the engine to 4000).

I really don't think my belt is slipping, and the unit is designed to reuse the pulley from the generator so it can't be just oversized. Anyway, at 4000 rpm I should be seeing 14v regardless and I'm not.

Looks like I'll have to ship it all the way back I was really looking forward to seeing the back of the generator (which isn't charging either).

I wonder if there is any way of testing the alternator alone. Clamp it in a vice, connect a multimeter between the case and the output and spin the alternator with say an electric drill with a buffing pad on it.


Wild Guess: Maybe they shipped you an unconverted dynamo by mistake?

Edit

Removed to to my stupidity...

John

Hi I'm reading this as I have also just fitted a Dynamator and had to change from positive to negative earth.

Jury's still out as I have not managed to get the car to start yet. I think the condenser has gone bad after the polarity change.

Anyway , You should get 12V+ at the terminal if its connected to your solenoid. If its disconnected then maybe not because there's no load. If your ignition light is going out that indicates a reversed current and so the Dynamator is generating (Good thing) , assuming you have connected the Field output of the Dynamator to the Brown/Yellow wire from the regulator box.

I discontected the A terminal on the regulator at spliced the wires together. I also ran a wire from the solenoid to the A1 terminal and left the other wires connected (Headlamps etc) , I read that this should be done although I have a doubt as its now not fused.

Hope this helps Steve 1969 Elan

Hi again

If the generator did not work as well it does suggest something that is common to both i.e. the wiring could be wrong.

Testing a generator either dynamo or modern alternator with its internal controller and rectifiers ( which I think the dynamator is) is readily done with the generator in a vice ( good and firm) and use an electric drill, with a speed controller, with a socket extension bar in the chuck and a suitable socket on the end the machine can be driven form an electric drill-- but hold drill good and firm! connect up as the diagram I have attached. I have tested many alternator for problems with the idea in the attached sketch and it certainly seems to work fine in sorting out rogues. when I test this way they have been totally duff or perfectly OK. Above about 1000rpm they usually give enough output to raise the battery voltage OK

Hope U fine the problem and dont have a duff un

best of luck

Bob

Bob,

That's really helpful thank you! Was mulling the same co-incidence. I'm going to try that with both the generator and alternator.

M

Digital Volt Meter, I expect.

i.e. a multi-meter set to say 20 volt range.

billwill wrote:I wonder if there is any way of testing the alternator alone. Clamp it in a vice, connect a multimeter between the case and the output and spin the alternator with say an electric drill with a buffing pad on it.

While checking whether or not this was practical (i.e without a battery) I found on the net this diagram which shows the internal circuitry of a standard alternator.



From this, to me, it is clear, that you definitely need a battery there to get the alternator started. The voltage from the car battery causes current through the indicator light which feeds the transistors (which are the generated voltage regulator) at top left, which in turn control the field current (in the rotor) via slip-ring brushes.

The strength of the magnetic field in the rotor determines how many volts the stator coils generate, the alternating voltage/current from the stator coils is rectified be the 3 left diodes and the 3 right diodes to produce the main output at the terminal marked +

Meanwhile an extra set of diodes (centre set) also rectify the generated output and feed it back to the input that came through the bulb, this (via link IND->F) takes over supplying the current to the regulator (and hence the rotor field), which is no longer drawn through the bulb and the indicator light goes out.



~~~~~

There are lots of bits to go wrong in there.

An incidental consequence is that if your ignition indicator bulb fails or is not connected properly the alternator will not get started and you won't charge your battery.


"For want of a nail a shoe was lost ..... " etc.

I'm not sure about this, but from that circuit, I suspect that if you were ever to accidentally connect the F and earth wires, of a negative earth alternator, even briefly to the battery, before you had reversed the battery connections, it would destroy those transistors in the voltage regulator and the alternator would not work after that.