National Rally

Re: National Rally

Postby luli » Tue Jul 23, 2019 9:22 pm

Test the dynamo: Loosen the belt or remove it from the car, connect the armature and field together, the body to ground and the armature/field to the battery. the dynamo should turn, quite fast. If it is OK return it to its place, reconnect wires, remove the cover from the control box and start the engine. When you increase the engine speed the cut out relay should close. It is clearly seen. If not, check the connections, including ground (E). without good ground it wouldn't work. If it is closing and steel no charge, the cut out is oxidize. You can also connect temporarily F and D. If you get very high charge then the control box is bad.
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Re: National Rally

Postby RobHomewood » Wed Jul 24, 2019 12:06 pm

Thanks Luli
That information sounds very useful to me as my understanding of electrical stuff sometimes eludes me!
I will try what you sugegst but it may have to be after i have been away
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Re: National Rally

Postby RobHomewood » Sat Jul 27, 2019 11:39 pm

Well now. I followed Luli's suggestions. I tested the dynamo- running fine - not super fast but steady, as was the spare I tested also. I tested the earth and even added a wire direct to the engine from the control box and I attached the control box breakers whilst revving but nothing moved. Then when I was putting the fan belt on for the last time I noticed it was cracked- in fact it turned out that only the outer fabric was holding it togther so I thought I had found the problem, embarrassing though that would be. However when I fitted the new belt today it made no difference.
So I swapped in a third control box, again without any change- no positive charge.
My focus now is on the ammeter itself. I have a spare so I will swap that in once I have worked out how the release the meter- it looks like it may have lugs which you have to turn the whole body to allow the meter to come out of the front of the dash. Can anyone confirm please?
My last note is that when I went this evening to fill up the tank the ignition light was just about going out under power showing I presume that some current is getting through to the battery.
I have given up now as I am going on holiday but will resume after- hopefully with more success. More thoughts please
Rob
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Re: National Rally

Postby luli » Mon Jul 29, 2019 7:53 am

You can temporarily short (by-pass) the ammeter to see if it helps before replacing it which is difficult. just connect A on the control box with the battery side of the solenoid. You can read here about the ammeter :
https://wp.me/pXLKy-258 and https://wp.me/pXLKy-3sc
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Re: National Rally

Postby RobHomewood » Mon Jul 29, 2019 1:38 pm

Thanks for that Luli. I shall look into it when I return from holiday
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Re: National Rally

Postby TonyG » Mon Jul 29, 2019 9:56 pm

Rob,

This one is a real puzzle! In my experience of electrical fault finding the seemingly elusive cause is actually more than one thing. E.g the original fault was the dynamo but by the time you changed it, a faulty voltage regulator unit has been substituted giving the same or similar symptoms.

I’m not suggesting that is actually the fault here. However, you do need to go back to basics and double check that everything is ok.
1/ First of all check all the connections, including earths, right from the battery to the dynamo including the solenoid and regulator - even the ignition switch if you can get to it. A high resistance connection might cause a problem if, say, insufficient power is getting to the field windings of the dynamo.
2/ You said that the wires to the dynamo were ‘ropey’. For the same reasons above, make sure these wires and any other in the main charging circuit are in good order. With the battery disconnected and wires removed from dynamo, check the continuity of the cables back to the regulator, using the resistance range on a test meter.
3/ Meanwhile, make sure the battery is fully charged.
4/ connect the battery and using the wiring diagram test the voltage at the battery and solenoid - these should read the same as the battery did when It was disconnected. Then again with the ignition on, the voltage should hardly drop but now you have a base voltage that you can easily trace through the ignition switch to the regulator and onto the field winding of the dynamo. If you don’t have this then check the regulator connections and contacts and wires to see why not.
5/ assuming all is correct, start the engine and test the output of the dynamo with the wire disconnected. If there isn’t one or it is low then the dynamo is faulty.
6/ I think I’m right in saying (Luli will correct me I hope) that the ignition light sits with 12v on it and lights to the earth in the dynamo when idle. Then as output rises towards 12v and the potential difference dimishes, the light fades and goes off.
7/ So if you have output at the dynamo and 12v on term D at regulator then, when connected, the ignition light should go out. If not, I can’t see why but you could try changing the regulator again although I think you will have identified the fault by this point.

All this will only take a few minutes testing.
Hope it helps and that you had a good holiday!

Tony.
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Re: National Rally

Postby luli » Tue Jul 30, 2019 5:47 pm

Hi Tony, I always like to read your comments which not only contain a lot of knowledge but are written nicely and in a positive attitude.
Dynamo is a self exciting device - contrary to alternator, and it will generate voltage even if the warn lamp is burned. Also, it is not recommended to run the dynamo without a control box and battery since it can generate very high voltage, up to the point of self destruction. You are absolutely right about the necessity of methodical, step by step diagnose of the electrical circuit. A common fault in control box is a disconnected resistor, this is why I suggested to short D and F temporarily.
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Re: National Rally

Postby TonyG » Tue Jul 30, 2019 11:36 pm

Luli, I knew I could rely on you to check my logic!
At point 5 I should have said disconnect wires and put link in D to F. Then start car and test for output at D. It should be at least 12v, probably 14v. If no output then dynamo faulty. To further test stop engine, remove link and re start. If output at D is 4v then fault is field winding or brushes but if zero then likely armature problem or brushes. I was getting these steps muddled a bit. My apologies, long time since I faulted on a dynamo and was writing while tracing circuit on diagram.
I guess if you put the D to F link or short in at reg box, as you suggested, and get 12-14v reading this proves the dynamo and wires.
So what causes the ignition lamp to glow and then go out if not as I said in earlier reply? I'm clearly a bit rusty on the finer points- my Dynamators are making me lazy!

Thanks

Tony.
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Re: National Rally

Postby luli » Thu Aug 01, 2019 9:45 pm

hi Tony,
Contrary to alternator (or Dynamator) dynamo is a self exciting device, so it will generate voltage even if the resistance of the main switch is high or the warning bulb is blown.
See more here https://wp.me/pXLKy-lS and here https://lulisml.wordpress.com/2015/05/06/daynamator/
In both circuits there is full 12V on the ignition light when the the engine is not turning, and 0 when the generated voltage is equal to the battery voltage.
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