The Fordson Tractor Pages Forum

I noticed last night that the battery cable going from positive to the starter solenoid, the plastic sleve had melted.
I have also seen some sparks comming from the starter solenoid when I start the engine.

If I had putt the battery the wrong way, without truning the polarity of the system, would everything work?
It has charing light, oil light, light inside the tachometer, charing (low charing, but it charges), the front lights and everything else works.
Could I then have put the battery back the wrong way? At what volt should it charge?

Thanks a lot

It is right on your Dexta with Lucas system "minus" to solenoid, and "plus to ground. -If you try to change to "normal" you have to chang wiring at the regulator, and also make plus to minus on the charger too, the rest will be ok...I suppose.

hi
usually i tink

a dynamo system has a + earth so - to the solenoid.
so systems like on mine have a altanator so are negative eath.
which is urs ?

charge systems should be 13 volt plus at say 1500 revs i think drop to 12.5 ish and hold that , when engine swiched off.

the battery terminals are diferent sizes at the battery end .
a bulb will light either way around ( i think ,my test lamp will anyhow)
if u cross polarity u will get megga sparks - welding ect. not a gd plan , the gas coming of is hydrogen i think !!!!! as in a bomb my dad had one explode on him years ago .while puting it on charge.

so i guess if ur charge light goes out then chech the voltage across the battery with a volt meter to see if its charging / at what rate , but if the light goes out it prob is .

tom

A dynamo system can be either positive or negative earthed and the components will all work the same but the dynamo has to be polarised to the system.

If a positive earthed dynamo is put on a negative earthed system, or visa-versa, the dynamo, regulator and possibly tractor and shed will burn out, if it is run for any time!

Every time you fit a dynamo, even if it is brand new, you must polarise it to your vehicle. It is so easy. With the dynamo bolted to the vehicle but without the wires connected, run a wire from the output terminal of the battery to the "field" terminal of the dynamo. Hold it there for 10 secs. Job done. Then connect the wires.

Thank you Brian

Thanks for the answers,

I have run it this way all last winter, and have only seen sparks when I start it. But everything works. But I guess these sparks are a indication that I put in the new battery the wrong way. Could you explain what is the "field" terminal on the dynamo?

Are the battery terminals and solenoid terminals clean and tight?

The fact that the solenoid terminal has suffered as a result of heat tells me that its more likely a high resistance joint or a bad crimp (note the battery terminals with screw clamps for the cable are particularly bad for this).

I am surprised that you can see a spark from the solenoid although there will be some (but thet are normaly internal over the contacts) as the back EMF from the starter and solenoid coil will cause a spark.....which leads us back again to a bad joint.

So check the joints and measure the terminal and cable resistances.

Ain't there a way I tell for sure if I have put the battery in the wrong way?

Have you changed the battery leads or terminals?
As the terminals are different sizes, if you haven't changed them the battery must be the right way (or at least the way it has been for a long time)

You guys are correct, there was a size difference positiv and negativ. It must have been a bad connection on the positiv cable. I made a new cable, bolted them down thight and the sparks are gone And I'm happy waiting for the first snow to arrive
'
But it still only charges at 11.95v, hmmmmmmmmm