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Morry Generator System

 
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Boeing Bob
Got the hang of this ...


Joined: 08 Jul 2007
Posts: 284
Location: SYDNEY, AUSTRALIA

PostPosted: Mon Mar 04, 2013 8:34 pm    Post subject: Morry Generator System Reply with quote

To many people, electricity is understandably a ghastly tin of worms. To me it has been a way of life for my 52 years spent as an aircraft electrician and avionics engineer. Electricity is not only a powerful tool, in this day and age it is also a vital one. It can be manufactured in large quantities to power up huge cities or in small quantities for your hearing aid or watch. In our case, it's what gets our Morries up and keeps them running, with the help of a few other things of course. From comments on this site and others, plus enquiries from club members, it seems that there is generally not a great understanding about the generator system in cars so let’s try and remove some of the mystique about the Morry generator system.

We all know that the battery is the cornerstone of a vehicle’s electrical system and that to keep it usable and ready for use, it must be kept charged. This is essentially done by a generator driven by the engine. But what controls the output of that generator? Well to answer that simply, a device called the generator regulator unit, so let’s have a bit of a look inside that unit. To keep it short and simple, I will only describe the basic operation and not get too technical.

If you remove the cap from the generator unit mounted on the Morry bulkhead, you will find that it contains two coils which each operate a set of points. The coil on the L/H side facing the unit, is the voltage regulator. The points on the regulator control current to the generator field winding and the points on this unit are normally closed. As the generator builds up speed in accordance with the engine speed, the current in the field increases and the generator output voltage also increases. When the voltage reaches the pre-set value of the regulator, which is a nominal 16.5 volts on no load or about 14.5 volts under load, the points start to vibrate and thus control the current in the field circuit and consequently, the output voltage of the generator. Simple as that.
The other coil is the reverse current relay (RCR). The points on this unit are initially open. As the voltage builds up after engine start, at a voltage just above battery voltage, the points of the RCR close to connect the output of the generator to the battery to keep it charged and also to supplement the battery supply to all of the electrical systems within the vehicle. When the engine is stopped and there is no output from the generator or the idle is set low and the generator voltage falls below the battery voltage, the battery starts to discharge into the battery and the reverse current flow causes the points to open thus disconnecting the generator from the battery and effectively ensuring that the generator is not burnt out or the battery flattened.

The red light that we know as the ignition warning light is somewhat of a misnomer. Sure it tells us when the ignition is on with the engine stopped but normally goes out once the engine is running. This light is actually an indication of the generator serviceability as it is directly connected between the battery and the output terminal of the generator when the ignition is on. Most of the time, this light will be out when the engine is running but may glimmer very dull with the engine idling. This may not necessarily mean you have a generator problem but simply that your engine idle speed is a bit low. If it stays on with the engine at higher revs, it could be either an indication of a generator failure or a broken fan belt. Should the light go out when the engine is started and come on dimly when the engine revs are increased, it could be that the regulator voltage is set too high or that the brushes in the generator require attention.
I hope that this information is of some use to everybody . If you have any questions, please do not hesitate to ask.

Boeing Bob.


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stolzie
2nd gear


Joined: 05 Nov 2012
Posts: 62
Location: Gold Coast Australia

PostPosted: Sun Mar 24, 2013 4:36 pm    Post subject: Reply with quote

As above nice post. I figured this would be the best place to ask after a search on the forums.

Is this the correct procedure for testing the generator whilst on the car?

To test the generator, unplug the large and small Lucar connectors from the back of the unit. Connect a jumper wire with alligator clips from the small terminal to the large terminal. Connect a volt meter from this wire to ground. Start the engine and from an idle SLOWLY increase the engine speed above an idle and watch the voltage on your meter. It should rise slowly from 12 volts to about 17 with an increase in engine speed. DO NOT exceed 17 volts. If you get a continually rising voltage reading as engine speed increases your generator is OK and the issue is probably with the regulator or wiring between it and the generator. What this test essentially does is allow the low residual voltage output of the armature to energize the field at increasing levels.

I have tested mine like this as my IGN light is constantly on even at high revs and I am not getting anything out. So I suspect the generator.

Thanks,
Jason


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Boeing Bob
Got the hang of this ...


Joined: 08 Jul 2007
Posts: 284
Location: SYDNEY, AUSTRALIA

PostPosted: Fri Apr 19, 2013 8:20 pm    Post subject: Reply with quote

Hi Jason,

The procedure which you have mentioned will work okay as what you are doing is simply bypassing all of the control system and putting armature output straight into the field which will produce the effect as mentioned, ie, an unregulated output increasing with engine revs. If you are not getting any output, then the generator is definately cactus.

Boeing Bob.


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