Any classic vehicle wiring experts?

[t8hants]

I am trying to work out why my 1943 Morris Commercial C9 will not show a positive charge, I have tried three voltage regulators.
One of the things that I am curios about is why on the diagram does both the D+ and D- on the dynamo show as going to earth, as well as to the Regulator for the D+
The only thing I can see is the D+ earth has the symbol || across the wires which I thought may depict a capacitor in the system, but I don't know for certain why a capacitor would be in an earthed cable.
The slightly smaller sister vehicle the C8 has only one dynamo earth coming from the D+, the D- going to the regulator instead, despite the fact they are both negative earthed vehicles.
I'm confused :?

Thanks anyway......Gareth

 

[sunnybob]

Dynamos are completely different to modern alternators. You should have a separate black rectifier box between the dynamo and the battery,
https://www.howacarworks.com/electrical ... ing-output

 

[t8hants]

The Morris is way before alternators, what I am trying to fathom is why both D terminals are apparently earthed and what is the significance of the || symbol on the D+ earth, See below

 

[Distinterior]

This symbol -||- usually signifies a Capacitor......acting as a supressor maybe????

 

[HappyHacker]

The capacitor does not allow DC current to pass but will suppress any spikes or AC output, it is usually very small as it is only a suppressor. The dynamo is DC output. There are no rectifiers in the control box it controls the charging of the battery. Is there output form the dynamo before it get to the control box? the brushes may have gone. Its a very long time (>40 years) so I may have made a mistake in the above but I don't think so.

 

[banjerbill]

This symbol -||- usually signifies a Capacitor......acting as a supressor maybe????

+1 for capacitor. The earth is for the capacitor not the dynamo terminal, I believe, but stand to be corrected.

Bill

 

[geoffshep]

You might also need to be sure whether it is negative earth - many early cars were positive earth.

 

[dickm]

From (far too many!) years working on what are now called "classic" cars, but were generally "heaps" in the old days, your problem sounds much more like dynamo than control box, though the latter are not unknown. Do you have a meter of any sort, to check that the dynamo is actually putting out some current, between the D and F terminals. If the suppressor capacitor is shorted, that could also upset things. But disconnecting that won't do any short term harm just to test.
If the dynamo isn't putting out any current, it's potentially either the brushes (fairly easy to replace; at least they were on my various Volvo 120s) or internal wiring, which is probably terminal (in the dead-and-gone sense). I'm guessing the dynamo in a Morris Commercial of that age is probably much the same as on the old Minors, so that might be a source of a spare if your's has gone to the big scrap-heap in the sky.
If the dynamo is OK, then you need to open the control box (on old Minors there was just a wire strap over the top) and see what the two contacts do when the engine is revved. One should open at higher current, to "regulate" it. If neither moves, then it's either dud coils or maybe dirty contacts.
Hope this helps.

 

[t8hants]

Thanks all, the dynamo meters out as working well, and is a big old CAV model, made into the timing chain, you have to remove half the front of the truck to get it out and hold the chain precisely in place or you loose the timing.

An interesting thought that the capacitor may be shorting out is an interesting one.
On idle the engine has a discharge of 2amps, if you push the regulator reed switch down the discharge increases to 7amps we have tried turning the ammeter round just to check its in the circuit correctly