Classic cars forum & vehicle restoration.

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

Hi Sorry me again
measured the voltage with the engine running on tickover and got about 7volts

measured the voltage from the dynamo with dynamo disconnected and the f and d jumpered and got 3 volts

Everything seems to work however, charges the battery and light.
Trouble with the indicators but that another story

I'v rang rounds and due to the age of it (80 years old) people are saying it will need a rebuild which is about £400.

leave alone, service it, get a new one or have it rebuilt???

Steve

peter scott · Joined: 18 Dec 2007 Posts: 7118 Location: Edinburgh

Hi Steve,

Connecting F to D and driving the dynamo is a little indeterminate. It depends on the residual magnetism in the field pole pieces. If that is low then the dynamo may never gain enough field magnetism to get going so to speak.

You need the battery voltage on the F connection to get the dynamo started. If you just flash the battery onto the F connection then connect F and battery to the D terminal then remove the battery I think you will get a much higher output but it's a bit meaningless.

The key question is "can the dynamo generate enough current (amps) to charge the battery and light the lamps etc when connected normally?"

If the answer is no then you might need to check that the brushes are long enough to still contact the commutator under the spring pressure. If dynamo output is seriously low then you might have a shorted turn in one of the windings and that will probably require expensive specialist repair.

HTH

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

Thanks Pete
just had the inspection cover off and a wire fell out. it looks like it should have connected one of the field windings to the terminal. diy repair or specialist

other wise its clean and plenty of life in the brushes

47Jag · Posted: Tue Mar 14, 2017 11:42 pm Post subject:

Steve,

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

The old dynamo has gone in for repair, he said ring me on Friday.

I have a spare dynamo which seemed to test okay i span it up with a drill and got 14v off the car with the f and d jumper test.

I put it on the car today every seems to work as it should a part from you need to do about 3000 rpm for the the ignition light to go out and the points to close

47Jag · Posted: Sun Mar 19, 2017 7:17 pm Post subject:

Steve,

The cut-out should be adjustable by bending the tang that holds the spring or it may have a screw adjustment. It sounds like the spring tension is too strong just now. While measuring the voltage, rev. the engine until you see 6.5-7 volts on the meter, loosen the spring tension until the points close. This should happen ar around 1500-1750 rpm. The car is 6 volt isn't it?

Art

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

Thanks

No its 12v posative earth

47Jag · Posted: Mon Mar 20, 2017 11:06 am Post subject:

Steve,

OK, so try and get the point to close at 12.5-13 volts.

Art

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

no joy, only getting 0.5v on tick over across F and D.

47Jag · Posted: Tue Mar 21, 2017 1:08 am Post subject:

Why are you measuring across F & D? What do you get across D & earth?

Art

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

only getting 3 or 4 volt D to earth on tick over

47Jag · Posted: Fri Mar 24, 2017 11:18 pm Post subject:

Does your charge rate get varied by the main/headlight switch? Or is it a basic 3 brush Dynamo where you adjust the charge by moving the 3rd brush? Look in the window at the end of the Dynamo and see if the 3rd brush is mounted on an adjustable block? I can't remember which way you move it to increase the charge (I'm old Very Happy

) but it should be obvious if the voltage/current increases or decreases. Did you do as Peter suggested and flash the D post?. What happened to the 14 volts you had prior to installation?

It's difficult when you are not there to see the results.

HTH

Art

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

It is a C45 P10 part no. 224458

when i test it off the car with a battery drill seems fine easily gets 18v and i think would go higher

i dont have any lights connected yet. the position of the 3rd bush is adjustable but it did not make much difference

i have flashed it to the field terminal

47Jag · Posted: Sat Mar 25, 2017 9:40 pm Post subject:

Steve,

So you can get voltage off the car but when you install it the voltage disappears. I had a look back on the posting on this thread and it suggest that there is a problem with the car wiring. What car is it anyway? What type of regulator/cut-out is fitted. If your meter has an OHMS scale can you measure between the D wire (disconnected) and earth. I would expect something around 24 ohms or slightly higher which would represent the cut-out coil. If you could do that and report back we may get a better idea what is happening.

Art

stevefizz · Joined: 26 Jun 2015 Posts: 30 Location: Loughborough

Hi

got about 30 ohms

it is a Vauxhall DX 1938

https://drive.google.com/file/d/18GtoP_0HjdP6EDOAQKs8mLzI7zEzUz85-A/view?usp=sharing