POS or NEG ground

[French Tickler]

HI, how can I tell if a Citroen H van 6 volt, 1954 year, is pos or neg ground. The battery was not in it when I looked, so cant tell from that.
thanks.

[Stewart(oily)]

Maybe measure the diameter of the battery clamps, they are different sizes.

[addo]

All my Dee references show negative ground, that only covers you for 1956 onwards though.

Can't work it out off the battery post clamp inner diameters?

[Stickyfinger]

Marked on the regulator ?

[French Tickler]

Hi, thanks for the replies, but the battery terminals are the same size, so no joy there.
Just out of interest, what would happen if I connected it around the wrong way?

[exect]

As I remember from vehicles of that age there is not much that can be damaged by wrongly connecting the battery, only maybe the radio if its turned on.
The starter motor may turn in reverse and that would tell you what you want to know.
If it does have a radio (Probably valve with multivibrator powering) and you are up with electronics you can work out the correct polarity from this.
Exect

[Mandrake]

As I remember from vehicles of that age there is not much that can be damaged by wrongly connecting the battery, only maybe the radio if its turned on.
The starter motor may turn in reverse and that would tell you what you want to know.

Isn't turning some engines backwards dangerous for their health ? When doing cam belts its always recommended never to turn an engine backwards.

There must be an easier and safer way to determine the polarity...

[Xantidote]

I ran a 1962 Austin Cambridge (A60) a few decades ago, and once refitted the battery the wrong way round. Car was fitted with a dynamo.

I only discovered later that day that the battery was wrongly connected, when I noticed that the ammeter was showing discharge rather than a charge, whilst driving. Engine and headlights were working fine. Immediately reversed the battery, and all right as rain again No engine running backwards, and never any subsequent odd behaviour

PS. Overhead valve, chain driven

[addo]

Simon, the Dee cam chain is tensioned by a semi-mechanical shoe so it's never going to go fully slack and skip. Plus you only need to bump the starter a smidgin to see which way it's rotating.

[BX]

Battery reversal is not a problem unless there is a radio fitted. Many old radios had option plugs for positive or negative earth. However it is a wise precaution to first of all polarise the dynamo before starting the engine. If you dont you run the risk of burning out the dynamo and the regulator. Changing polarity without polarising the dynamo is like Jay walking. Normally you get away with it but you may be knocked down. To polarise the dynamo disconnect the smaller of the 2 wires from the dynamo (probably marked "exc"). Then using a length of wire connect the dynamo terminal to the non earthed battery pole for about one second. Then reconnect the wire you removed. That is how It is done with the Lucas dynamo. I think that the Sev Marchal and the Ducellier dynamos are the same.
Most old starter motors are series wound and are therefore polarity independent (as are shunt wound and compound wound motors) It is only in recent times that suitably powerful permanent magnets became available at a price that made them economic to fit to starter motors. You shouldn't have to worry about reverse rotation. In addition the overrun protection in most pinions will not allow the engine to be turned in the reverse direction.
If the battery is fitted negative earth there is less chance of someone fitting it incorrectly.
If you wish to convert to 12V you need to change the regulator. aThe dynamo normally is happy to push out 12V. 12V negative earth means that you can safely use modern devices like sat nav and mobile phone chargers. in addition you should have much better headlights (remember to change all bulbs) Due to the higher currents and lower voltage involved a large percentage of the power is lost in the wiring to 6V headlamps. Anyone remember the 6V Beetle? It is better to change to a 12v starter motor and you must change the ignition coil.

[exect]

The above post gives the answer, if you remove the fan belt and spin the dynamo in its correct direction of rotation and measure its output with a multimeter set on low volts so that a reading is obtained, the leads of the multimeter will indicate the positive and negative.
Exect

[French Tickler]

all sorted, thanks for the tips guys.