Battery

[BLACKJACKф]

Does anybody have any suggestions or ideas why my battery keeps going dead in my 1968 Mark II Cooper S. The voltage regulator looks like it's set properly the Dynamo has been rebuilt and and battery is brand new 3 months ago.? Any help would be greatly appreciated.

[timmy201]

What’s the voltage when it’s running and when it’s shut off? Is the battery charging properly?

Have you measured the parasitic amp draw with the key off?

[woodypup59]

Either a short elsewhere in the wiring, or a fault with the voltage regulator cut-out.
Was it OK before whatever the last electrical work was done ? IE the dynamo rebuild.

[Exminiman]

…….as others have said, you have to measure the output of the generator and ideally do a drop test on the battery.

So you will need a cheap multimeter and ideally a drop tester…..its an easy check, even the young lads at Halfords can do it

[larrysimon]

Check for a Parasitic drain is the most efficient/fast way of identifying the cause, it may be that the battery is at fault and its age and previous use is no real indicator of its health.

Disconnect the Negative lead from your battery and connect your DMM in series between the negative terminal on the battery and the earth lead, measure in Milliamps .............from memory I think anything lower than 0.03 milliamps is ok.

Check the millions of youtube vids on how to do it.

[floormanager]

I gave up with mechanical voltage regulators as I could not get them (new ones) to work. My lights used to gobright and dim. I fitted an electronic unit
https://www.dynamoregulator.com/products.html
Works perfectly, get 14V+ when driving along.

[BLACKJACKф]

Which one did you get I mean the electronic when you got rid of the voltage regulator.?

[BLACKJACKф]

There was a problem with charging the battery before the Dynamo rebuild that's why we did that it ran fine since last July.

[BLACKJACKф]

The battery is brand new only 3 months old car ran perfectly started every single time then just one day battery dead no starting. I was wondering if the not starting was an issue with solenoid as it wasn't clicking at all. When I put test light onto the white wire with red stripe turned ignition full on test light came on so looks like power from ignition switch to solenoid. Currently checking for any other loose wires or shorts in system.

[Tim]

Are the battery terminals clean and done up tight? Its amazing how a dirty or loose terminal can test perfectly with a multimeter, until you try to drag a heap of current through it.

Tim

[mk1]

You can check the obvious things, like a nipped battery cable under the car, but you really need to get a clamp on ammeter onto the battery cable, to see how much current is being drawn when everything is turned off. There are some decent suggestions here, but without measuring the amperage, you are shooting in the dark a bit.