Urgent help needed... won't start

[Robin Bristol]

Got the JCB 3C down here to Bristol yesterday and it started and drove fine off the lorry. Started this morning OK and after an hour or so I noticed the idiot lights glowing (Gen being one) I shut down for a while and when I tried to start it the battery was way too flat. Had to buy a new one £85... and once fitted started right up. Ran fine for an hour or so no lights etc. so when I stopped it for a 45 minuet break I was devastated the new battery wouldn't turn it over. Now it is stuck in the lane so no one can get past... I have called a friend to go buy some jump leads and come over.... but what is going on?

[TullyveeryClassicJCB]

From memory your digger is a 3C mk1????? If so you should have a dynamo and regulator. If your regulator packs in your dynamo will put an extremely high voltage charge into your battery which will harm your battery temporarily.

[Robin Bristol]

That makes sense... the kind of answer I was looking for. Now How do I test it? I got a jump start and have driven it off the lane into a neighbours garden (very temporary solution). I am suspicious that given a long rest the battery seems to recharge enough to start it... Anyway I have put the original battery on charge overnight so I have some options tomorrow. I will search for a regulator and dynamo on line and see if anything comes up. They look a lot like the ones on my old Ford Zephyr V6 motor (same era), so they might be easier to source.

[Mrsmackpaul]

I would always test it before changing bits

does the battery get to hot to touch as in boiling the guts out of it ?
is the regulator switching power on to the alternator ?
what voltage is the battery at when it is running trying to measure it at different speeds of the engine ?

Paul

[Robin Bristol]

Definitely Dynamo and voltage regulator not Alternator.. Positive earth too. Can't say I have tried touching the battery while it is running. I have a lot of things to try in the morning... and starting with checking all the wires are still in place and then putting a volt meter on the dynamo.. although I haven't seen that yellow light since the first and only time. I suspect it is running off the battery and not using power from the dynamo.. I just might have turned the ignition key back a notch (like you do in a car) while running apparently that will stop it charging. I am very grateful for any and all suggestions this is all new to me.

[TullyveeryClassicJCB]

On a tractor I have I just disconnected the wires from the dynamo until I got a new regulator.

[TullyveeryClassicJCB]

When you put the volt meter on check the voltage at different stages. With a faulty regulator the voltage starts off at 12v and then enters a spiral of growth. It took my tractor around 15 minutes to reach 18 volt.

Another thing, that original battery, be careful about charging it. You would be better to let the battery cool off, settle and let it recover from being charged at an incorrect voltage.

[Robin Bristol]

I had the battery tested at the suppliers... they said it was fine just low and needed charging up.. sat around for 6 hours before putting it on trickle charge overnight... should be fine.

[Robin Bristol]

It started first time today... this is definitely a case of the battery acting (or being) discharged while running and taking a few hours to recover. Knowing it is a brand new battery and the same thing happened to the original (which is now charged and perfect) the fault has to be with the Dynamo the Voltage regulator or wiring between. Panic over, the machine is now in our field and out of harms way... peace returns to the neighbourhood and I have time to consider my options.

[agrimax]

You'll probably find that the cut off contacts inside the regulator will have stuck closed creating a short circuit and discharging the battery.When the battery has discharged enough the contacts may have opened again and started to work correctly again. Probably handier to replace the regulator(control box) than to mess about inside it as they can be quite sensitive to set up correctly.They're not overly expensive.