Intermittent weird starting problem

[C.J.]

1961 1098 Moggsy.

Invariably....but NOT always, the battery appears to be nearly but not quite flat if it hasn't been run for a day or two.

Interior, oil and charge lights all dim.

Put it on charge, and within 30 seconds it's showing fully charged
Had the battery checked, and it's in good health, as is the alternator, pumping out a more than acceptable amount of charge.
As was suggested, disconnect the alternator (yellow cable) to make sure it isn't somehow draining the battery whilst turned off.

It isn't and made no difference, but the battery is fully charged within seconds again anyway, so it surely can't be a voltage drain

Everything connected tight and properly.

Ideas as to what should be checked next?

Starter motor perhaps?
But once again, why is the battery regaining full charge within seconds?

Never known anything like it. Totally bamboozled.

[katy]

Sounds like a poor connection somewhere, possibly at the battery, or where the other ends of the battery cable connect, or maybe the earth strap between the chassis and the transmission.

How old is the battery? It may be the battery acting up.

[C.J.]

Sounds like a poor connection somewhere, possibly at the battery, or where the other ends of the battery cable connect, or maybe the earth strap between the chassis and the transmission.

How old is the battery? It may be the battery acting up.

Had the battery tested yesterday, as i REALLY thought that was going to be the problem, but it's holding its charge and is in fine fettle, as is the 12 month old alternator that's pumping out 14 volts...or is it watts?
The power is leaking away somewhere while turned off, but that doesn't explain why it's only taking a very short time to regain its charge.

I thought it must be the starter motor, but if it was that, surely it would just click as if stuck

Think it's going to have to go into an auto electrician.

[C.J.]

Always said electricity was introduced by aliens, and this proves it.

[Trickydicky]

Must admit I'm with Katy on this, poor connection or bad earth. Try cleaning the earth straps from the battery and the one on the gearbox.

[C.J.]

Must admit I'm with Katy on this, poor connection or bad earth. Try cleaning the earth straps from the battery and the one on the gearbox.

Why when it's started then, does it behave for the rest of the day?
Surely if it was a dodgy earth connection it would misbehave virtually every time?

[amgrave]

Years ago I came across a battery with the same symptoms. One of the connections inside it between the plates had come loose but you could not see it as it's inside. One minute it would behave as if it was flat then it would appear to be fully charged. This happened because the connection was making and breaking. Only spotted it some weeks later as it had a translucent case and in the evening I noticed a spark from inside it while fiddling to find the fault.

Maybe this is the problem.

[C.J.]

Years ago I came across a battery with the same symptoms. One of the connections inside it between the plates had come loose but you could not see it as it's inside. One minute it would behave as if it was flat then it would appear to be fully charged. This happened because the connection was making and breaking. Only spotted it some weeks later as it had a translucent case and in the evening I noticed a spark from inside it while fiddling to find the fault.

Maybe this is the problem.

Mmmmmm.

I know someone with a spare 2nd hand battery lying around..
I may try that and see if that's the problem then.

Never heard of it before, but hey, why not ey?

[amgrave]

If that is the problem it would be only the second time I have heard of it. Can't think what else could cause your symptoms.

[Trickydicky]

Most electrical faults are simply down to poor connections, when you start the car you need a lot of current from the battery to turn the starter. If you have a poor earth connection the circuit is not completed properly. Lights and other general connections can cope to a certain degree with a poor earth connection but the starter motor connection due to its current draw needs a good clean connection.

[amgrave]

In this post thought as the OP has said "Interior, oil and charge lights all dim" so it's not a starter problem.

[C.J.]

In this post thought as the OP has said "Interior, oil and charge lights all dim" so it's not a starter problem.

logical.

I shall attack with gusto tomorrow.

[bmcecosse]

Almost certainly -battery knackered. Next time it charges up, test it by cranking the engine -with a wire off the coil. How long does it last ? Two or three turns? or 'for ever' ?