BATTERY GOING FLAT

[rsawatson]

Evening. I'm looking at a friend's Minor for her (1956); the car is cutting out and not starting again, but I'll give a bit of background info first.

Before Christmas, my friend returned to Germany for about 6 weeks when the car was left standing without being started. Not surprisingly, on her return in the new year it refused to start - (a) because the battery was flat and (b) because the fuel pump had ceased working. I got the fuel pump going again, jump started the car, and all was fine for a while.

About a week later, I got a phone call saying that the car wouldn't start - again the problem was a flat battery. When I jump started the car, and revved the engine, my voltmeter was showing an increase to about 14.5v across the battery. To my mind, this showed that the dynamo was working properly, so I diagnosed the cause as being a worn out battery and we bought a new one and I fitted it. Again, fine for about a week or so.

A similar problem is occurring again. I got a phone call to say the car had cut out, whilst depressing the clutch when doing a three point turn, and then wouldn't start again. I 'went to the rescue', waited a few minutes, pulled the starter and the car once again fired up. But, with both the lights and wipers on it cut out, and again refused to start (as in starter pulled and absolutely nothing happening; at best a couple of feeble turns of the engine). It started off the crank handle perfectly fine after this.

The red ignition lens on the speedo is always illuminated when the engine is idling. However, as soon as the engine is revved, this light goes out. When the headlights are one, they get decidedly brighter when the engine is revved. This is normal, right? Does this not prove that the dynamo is working? (I have noted however that the ignition light is always off on my 1968 Minor, even when idling, and the difference in the brightness of the headlights whilst idling/revving is not nearly so great as it is with my friend's).

I'd be grateful for your opinions/suggestions for finding the cause. Do you think the battery going flat is a case of too many short journeys in the dark? Too low an idling speed (though this seems healthy)? Dodgy dynamo/voltage regulator?

Help would be much appreciated, as I want to get it mended for her as soon as possible!

Cheers.

[bmcecosse]

Yes - normal for the red light to be on when idling and for the lights to brighten when revved up. Will be more noticeable when the battery is flat of course. Lift the idle speed slightly and check the fan belt is tight. Also - instruct the driver to NOT use the headlights in town - only when doing a decent speed. If the car is doing lots of town use with heater/wipers/side and headlights on then the battery WILL go flat. The answer of course is to fit an alternator....... But limiting use of headlights should help greatly meantime.

[rsawatson]

My gut feeling is that there's nothing wrong with the car; it's the way it's being driven. I'll check the fan belt etc tomorrow, but I'm pretty confident that all's well dynamo/voltage regulator-wise. I would add however that this has all happened in the space of a couple of weeks - would such a short time give a brand new battery the chance to discharge if being driven with all electrical accessories on?

Thanks for the sound advice as always!

[bmcecosse]

Oh yes - easily!!