RK Saloon 1929.
Having spent time sorting out the wiring I am reasonably happy that the wires go to the right places! HOWEVER.... The lighting switch is a bit erratic! Mine seems to have four(?) positions and the results are a bit variable. Position one turns on the side lights. Position two usually lights two headlights, but can lose the o/s sidelight. Position three /four o/s headlight goes out, sidelights usually on.
I will check that the connections are going where they should again, but can someone enlighten me as to what I should expect to light up agaist which position?
Knowing how fragile elderly "plastic" & brass 7& copper can be I am nervous about dismantling the switch.
Oh & the winter/summer switch is a bit erratic, but usually the dynamo kicks in once the revs are well up.
David

Location: Stratford upon Avon

I would expect there to be three positions.
Pos 1: All off
Pos 2: Sidelights and taillights
Pos 3: Headlights and taillights (sidelights off)

The taillights have a seperate feed marked 'T' on the back of the panel. The sidelight feed switches off when the headlights come on so saving 2 amps.

Location: North Yorkshire

It is a long time since I dismantled one of these. So I think the following is right, but check before acting on it.

I think the switch knob is held in by a small nut which is accessible on the back of the unit.
The knob spindle has a couple of flats which engage with a dimpled brass plate which is what makes the connections. The dimples give you the "feel" of the switch positions, as they drop into corresponding depressions in the "plastic" body of the switch.
At the bottom of the depression is a brass rivet-like thing which goes through to contact the brass strips visible on the outside of the back of the unit.
The dimpled plate is kept in contact by a spring about 15mm diameter and about the same long.

My guess is that this is corroded or weak, giving you poor and erratic contacts. You should be able to check this by looking into the switch from the side, using a torch.

Or the switch could have jammed at some time, and the flats on the spindle, or the corresponding straight bits in the brass plate, be damaged.

Whatever, is is easily dismantled for checking.

Provided the fastenings are not corroded solid, I think the most fragile bits are the brass strips, which fracture, but which can be replaced or repaired.

Cheers

Simon

Location: On a hill in Wiltshire

Looking at the switch from the side will reveal the split pin which secures the knob to the switch. Removal of the knobs and the two bolts which hold the front plate to the switch panel will give you a better idea of the state of the switches and brass tracks. Removal of the ammeter terminal screws will reveal the countersunk screws which hold the ammeter in the panel. Releasing the nuts behind the switches will release them note their position before removal-they are handed. If the brass tracks are broken I've soldered heavy gauge copper wire across the breaks although I seem to think one of our cherished suppliers now supplies new ones. The best thing for cleaning the contact surfaces is a glass fibre burnishing tool, which modellers use, don't get the glass fibre particles get into your skin or eyes.

Thanks to you all. I must remember to label all the wires going into the panel- they are all black & unmarked! And take photos.
D

Location: Stratford upon Avon

Tony Betts can supply a new main brass track.

David

Thanks for the advice. The assembly came apart without problem & all the parts were intact! I now understand why it feels as if there are more than three positions. As you move from one point to another the dimple briefly is in contact with both terminals, it then makes positive contact with the target point.
Now to wire it all back together.
One further question....when the car was rewired in the 80's all the wires he used, except for starter leads, are 28.030 (28 strands each 0.03mm thick)This appears to be rated at 16amp. Is the considered opinion that this is enough? The wire from the battery to the B terminal on the ammeter concerns me as also does the dynamo output cables. I know that there is not much, but....?
David

Location: Stratford upon Avon

Just to (maybe) put your mind at rest, David. In it's original specification the car's entire electrical load, excluding that of the starter motor, would not have exceeded 16 Amps. The maximum safe output from the dynamo was approx. 8 Amps.

Ian Mc.

Location: Shropshire

That was encouraging!
Well it is all back together, wires connected & the lights work 100% correctly!
I have converted back to negative earth & need to get a new positive terminal over the weekend, then wheels back on & see if the dynamo still charges (& the ammeter reads the right way round!)
David

Location: Stratford upon Avon