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Hi everyone, 34Rp, electrics I don't really understand.
My ignition light won't go out and the ammeter shows discharge when going 30mph. The last time I used it it was fine. I've looked at the commutator it's nice and clean and the brushes look OK , the brush that is visible from above is just skimming the commutator, if i push it further on it makes no difference. The cut out, when are the points meant to open and close ? If I rev the engine and manually push the points closed the light goes out but shows more discharge ?
Any ideas greatly received
Joined: Aug 2017 Posts: 2,251 Threads: 33
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Location: Deepest Frogland 30960
Car type: 1933 RP Standard Saloon
The brush most prone to wear is the 3rd brush as it's half the thickness of the other two. It sounds like the dynamo isn't charging for some reason. You could try sliding the 3rd brush down slightly - that should increase the charging rate slightly if all is well. The two main brushes are at 180° to each other, the 3rd between the two others on the bulkhead side of the dynamo. It is on a sliding mounting so you can raise or lower the output rate.
Joined: Aug 2017 Posts: 2,251 Threads: 33
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Location: Deepest Frogland 30960
Car type: 1933 RP Standard Saloon
30-10-2022, 06:35 PM
(This post was last modified: 30-10-2022, 06:36 PM by Reckless Rat.)
Yes the brushes are held in with a screw on the dynamo shown, but they're not that easy to change if the dynamo is in the car, particularly if you drop one... The top one is reasonably easy, but it looks fine - the other two aren't that accessible - the 3rd brush is the one that's below the green wire in your pic. Be aware that if you remove the dynamo you will have to reset the timing. If you don't know what you're doing, have someone that does help you.
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Check all the obvious things first. I had the very same symptoms recently and found a broken wire to one of the brushes. Knowing absolutely nothing about electrics I was quite chuffed at having fixed it myself!
Joined: Apr 2018 Posts: 505 Threads: 129
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Location: Staffordshire
Car type: Ruby mk 2
Don’t forget Harry Hales excellent electrical guide purely for sevens.
Copies available on the forum
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31-10-2022, 10:39 PM
(This post was last modified: 31-10-2022, 10:40 PM by Dave Mann.)
With a non working dynamo I disconnect the wires to the dynamo and put a link wire between F and D and a analogue voltmeter between F or D and the dynamo case and run the engine. If I get a voltage above 6 volts, depending on how fast it is run, then I look elsewhere for the cause of the problem. If there is no volts I turn the engine to No 1 cylinder firing then remove the dynamo to the bench for a closer examination, trying to fix a dynamo on the car is very difficult.
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Where on the forum is the Harry Hales guide, please?
