11 replies to this topic

[soopercooper]

Although I only use my mini about once a week, it has developed an electrical problem.

Recently the battery has appeared to be a bit weak, and since the battery is only about 5 months old I put this down to little use of the car. Anyway, today, I was forced to jump start it, which was fine and a drove around all day today in it. Did at least 1 hours worth of driving. When I drove home, in the dark with the lights on, they were getting dim, when the engine was idling, then with the car sat as I was opening the garage, it conked out and didn't have enough juice in the battery to turn the engine over and get it started.

So, tested the battery with a volt meter, it said 12.15v which would appear to be enough, however I've stuck it on the charger for the timebeing. Any idea what the fault could be? alternator? or a short somewhere?

[Rob]

Sounds like alternater as this has happend to me before. Get the engine running again and put your volt meter back on and the reading should be about 13 to 14.5 volts. Any lower and your alternators knackerd or on its way out.

[soopercooper]

thanks for the advice, will have a go tomorrow after battery has had a chance to charge.

[cowboy]

another way to test is to put the voltmeter across the battery, check the reading and with the meter still on the battery, get someone to start the car, watch what the readings are if there is no change then you know your alternator has gone

[siggy]

It takes a standard alternator up to 8 hours driving to fully charge the battery.

Have you checked the acid level?

Charge the battery, start the car and run it turn the lights on and rev it up, if the alterntor is charging you should be able to see the lights brighten as you rev it.

Not the best way to check but usually good enough.

Siggy

[The Roadie]

Check your earth from engine to body, my car developed the same fault on the way back from Shropshire. It got back, then we got in it for my dad to give a me lift to work and it was completely flat.
We thought it was the alternator, or the connection to it, but after running two multi meters, one across the battery, one on the alternator . We found that the alternator was working fine and that it was charging the battery, but poorly, only 0.5v increase when at half throttle.
Rigged up a quick earth from the cylinder head to the body and it was great after that, working fine. Since got a new earth strap and the Sprite now has bright headlamps (at last!) and runs better too.

[dklawson]

Once you sort this out (which might also include a new battery by the time you're done) you may want to invest in a "Float Charger". These are not the same as a trickle charger. The Float Charger will put out a little over 13v and is limited to about 100 mA of current. When your car is used infrequently, this is enough to keep the battery "up" without the worry of boiling it dry from too much charging. I have a couple for cars I don't use frequently and it makes it possible to crank them right up after weeks of sitting. Of course, you have to have them parked somewhere that you have access to AC mains to plug the Float Charger into.

[mayfairman]

I agree with the Roadie check the earth strap connection in the boot,as i had a similar problem with my wife's and i even nearly got a new starter motor but then some one said check the strap which i did, it was rusted around the bolt so cleaned it up and hey presto better than ever and it cost nothing.
Try it and you should find your problems solved.

[soopercooper]

Thanks all, will have a look at the earthing situation. Left the battery on the charger last night, so will be able to start the car and test all things hopefully this evening.

[soopercooper]

Check your earth from engine to body, my car developed the same fault on the way back from Shropshire. It got back, then we got in it for my dad to give a me lift to work and it was completely flat.
We thought it was the alternator, or the connection to it, but after running two multi meters, one across the battery, one on the alternator . We found that the alternator was working fine and that it was charging the battery, but poorly, only 0.5v increase when at half throttle.
Rigged up a quick earth from the cylinder head to the body and it was great after that, working fine. Since got a new earth strap and the Sprite now has bright headlamps (at last!) and runs better too.

Are you talking about the earth connection from the battery to the car body, or is there another earth strap in the engine bay?

[The Roadie]

Well both I suppose. I had a problem with my earth strap from the front subframe to the body, so the engine had a poor earth, but could be the one in the boot too.

[siggy]

The earth should go from the engine to the body, NOT from the subframe to body, Remember that the engine is rubber mounted

Siggy