Power TO the dynamo!

[David.H]

Following my "Quick Panic" thread...Not so quick solution & still a bit of a panic!
The problem!
Switch on , start up  Runs. Ign warning light stays on & ammeter reads negative (and more so if lights etc on). revving the engine makes no difference, not even a dimming of the warning light.. 
Wiring checked...all in the right places: 
Continuity good from D+ on the swichboard to D on the dynamo. 
Continuity good from D+ on the switchboard to cut out D.
Continuity good from S on the switchboard to S(H) on the Dynamo.
with Ign on and engine not running; no 6volts at the dynamo D nor S and I think there should be on one of them???
Is it time to dis assemble the Switchboard & give it a good clean?
The car WAS charging happily on its last run up from Oxfordshire....since then I have "tidied up" some of the wiring, but nothing replaced...some Lego brick connectors replaced with more  suitable, wiring fitted properly into clips etc....
Wiring is all "armoured" pattern with decent length unarmoured tails where they go into the switchboard to avoid possible shorting ….

[Bob Culver]

The field and output wires can be linked directly at the dynamo. If the dyn is working but going nowhere it should produce well in excess of 6v to earth or light a headlamp bulb very bright at modest revs. If fully earthed it will produce no output so the check can be repated with the terminals linked but not wired to the car.(But The car must not be run for any period with the dyn isolated and volts at dyn high). Unlike an alternator the dyn does not need a current feed to start it, although there is a very little from the ign bulb. The cut out must have an earth connection.
Any dyn output dims the ign bulb. Is this connected correctly? ie to D

[Howard Wright]

Hi David

Seeing as you haven’t had a huge response to this I’ll wade in with my limited knowledge and less than extensive experience. Namely I have just solved this problem on both the RK and on the Brookfields.  

First job is to read the Cornwall A7 club site “charging refresher” and other articles on their site.  They are very good.  Next get an analogue multimeter as digital ones tend to be upset by the High tension interference from the running engine.

Next I would check all your wiring.  If it was working before it should work now.  The fault is unlikely to appear suddenly, more likely it’s something you have done.  Then recheck all the earths.  

Then follow all the tests on the Cornwall site.

In my case the RK dynamo was duff (armature windings shot) and on the Brookfields the dynamo brushes were not contacting the commutator properly.

Good luck

Howard

[David.H]

Thank you Howard,
Yes everything DID work, so I am likely to have upset something! My real question is whether with the ignition ON should a voltage go to "energise" the dynamo? (D+ to D) I am not getting any voltage to the dynamo D nor the cut out D, so I think the most likely culprit is that the switch panel is playing up and that maybe I have disturbed the wire between D+ and IGN on the switch panel.
John Cornforth wrote to me at length about a similar problem on another car (turned out to be a faulty cut out coil!)
Cars like to do this just after you try to sell them.....!
I think I will dismantle the switch panel (I can almost do it blindfold now!)
The Cornwall article is excellent.
Thanks
D

[andrew34ruby]

Thank you Howard,
Yes everything DID work, so I am likely to have upset something! My real question is whether with the ignition ON should a voltage go to "energise" the dynamo? (D+ to D) I am not getting any voltage to the dynamo D  nor the cut out D, so I think the most likely culprit is that the switch panel is playing up and that maybe I have disturbed the wire between D+ and IGN on the switch panel.
John Cornforth wrote to me at length about a similar problem on another car (turned out to be a faulty cut out coil!)
Cars like to do this just after you try to sell them.....!
I think I will dismantle the switch panel (I can almost do it blindfold now!)
The Cornwall article is excellent.
Thanks
D

"My real question is whether with the ignition ON should a voltage go to "energise" the dynamo?"

answer is...  NO.   Unless I'm wrong.

[Stuart Giles]

My real question is whether with the ignition ON should a voltage go to "energise" the dynamo? (D+ to D) I am not getting any voltage to the dynamo D nor the cut out D, so I think the most likely culprit is that the switch panel is playing up and that maybe I have disturbed the wire between D+ and IGN on the switch panel.

You shouldn't be seeing any voltage at the D terminal with the dynamo connected. The only voltage headed towards the dynamo from D+ is that coming via the ignition warning lamp. it lights through the dynamo to the chassis earth. if you disconnect the wire from the dynamo D terminal and touch it to the chassis, the warning lamp should light if the ignition is turned on. 'A' from the switch panel should have battery voltage on it, but that connection only goes as far as the cutout until the relay inside operates.

Have you tried repolarising the dynamo? it's not unknown for the polarisation to disappear or even reverse if there is some play in the dynamo bearings. Polarise the dynamo by taking a wire directly from the battery live (positive on early cars) and touch it to the dynamo F connection, you'll see a small spark and the dynamo will be polarised.

---

Just to add to the above, do you have a half charge resistor somewhere in the circuit? as well as continuity as in my previous post you should see continuity from the dynamo field connection to S and when you either put the ignition switch to winter full or switch the lights to 'H' there should be continuity between The D wire and the field as the roller(s) in the switch panel should short the two connections together.

[David.H]

Thanks so much....I am cleaning up the switch panel & checking the brass Strips. I will have access to a decent analogue tester next week. ...so fingers crossed I will isolate the problem!
D

[Bob Culver]

Eons ago I had a dynamo which seemd to need occassional polarisng. (note the instructions in the Williams special book are wrong)
The cheapest, crudest, low ohms per volt analogue meter suffices. You will not be using it to adjust a voltage regulator! Much more useful for fluctuating voltages and dont have to buy batteries every few years!.

[JonE]

Cut outs.... does the CFR2 need any form of earth OTHER than its E terminal to earth? Its screwed down but wondered whether there is a hidden earth in the fixing mountings that needs testing.

[Stuart Giles]

Cut outs.... does the CFR2 need any form of earth OTHER than its E terminal to earth? Its screwed down but wondered whether there is a hidden earth in the fixing mountings that needs testing.

AFAIK, the only earth is via the 'E' terminal. If you have a meter, you should see continuity from the 'D' terminal to the 'E' terminal if the voltage winding on the cutout bobbin is good. The winding you can see on the cutout bobbin is the current winding, the voltage winding is in much finer wire on the inside, and is usually the one which seems to fail.