Electrical issues

Hi,

Posted a while back to say my series 3 ignition light stays on until the revs are quite high (about 35-40mph in top, whatever that equates to). Haven’t resolved the issue yet but the battery is charging, about 13.98V at tickover.

New problem now though. Couldn’t start it yesterday as the starter was cranking so slowly, too slowly to start. Assumed battery was flat so put it on charge and it was back at full charge in minutes. Even so, left it connected to charger (battery maintainer) overnight. Still cranking really slowly today, although it did start. Went for a short run (about 6 miles). After a run the cranking speed was much faster, about what it should be but whilst the engine was still hot. Could it be a bad earth connection to the body on the earth side of the battery that’s causing both issues? Or is it likely something else? Can’t even see where the earth braid disappears to, somewhere under the battery tray I guess.

I've had this problem for all the years I've owned my S3. It's had a new battery, 2 starters and new cables to earth and solenoid/starter. When it's been stood awhile it feels like a flat battery. My thinking is this, an old engine when turned off will often stop with the crank/Pistons in the same position, in my case the engine always seems to stop as No1 piston is just at the end of its compression stroke. If I turn the ignition key the engine struggles to move the piston any further until I hear the a sort of hiss from one of the valves as it opens. After this the engine usually starts ok. I've given up trying to solve it, I now think of it as an anti theft device. One day, I might adjust the timing to see if that as any affect. If you manage to find the cause, let me know.

Col

1980 Series 3 with 200TDi - I have the same - idling the red light is on, a few revs it goes out. Leave it for any length of time and the battery drains out but a quick charge and all good again. Is it just that an unhealthy battery also has problems charging (Red light)? I'll do a swap next weekend and report back.

Jimsky Korsokov said:

1980 Series 3 with 200TDi - I have the same - idling the red light is on, a few revs it goes out. Leave it for any length of time and the battery drains out but a quick charge and all good again. Is it just that an unhealthy battery also has problems charging (Red light)? I'll do a swap next weekend and report back.

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Sometimes my red light comes on whilst I'm driving and will go off again after a few minutes, I've plugged a volt meter into my power socket and it reads 13-14 volts with the red light on so I'm not worrying about it.

Col

Jimsky Korsokov said:

1980 Series 3 with 200TDi - I have the same - idling the red light is on, a few revs it goes out. Leave it for any length of time and the battery drains out but a quick charge and all good again. Is it just that an unhealthy battery also has problems charging (Red light)? I'll do a swap next weekend and report back.

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Likely an unhealthy alternator, next time you leave it disconnect the alternator and see if batt drains or not.

You could have a good point
4. Defective Alternator
A car alternator recharges the battery and powers certain electrical systems like lights, radio, air-conditioning, and automatic windows. If your alternator has a bad diode, your battery can drain. The bad alternator diode can cause the circuit to charge even when the engine is shut off, and you end up in the morning with a car that won’t start.

Thanks for the responses. The thing is, the battery appears to be charging properly. I took the battery out the other day because the starter couldn't crank fast enough to start the engine but when I put the battery on charge it only took minutes to get back to full charge. Tried it again last night with the headlights on. Started instantly and the headlights didn't dim, according to SWMBO so the battery must have been at full charge, even though the red light had been on.

Spoke with an acquaintance at the local garage today and he reckons it isn't unusual for the red light to stay on until quite high revs with small, old fashioned alternators. Who knows.

The other issue, the starter sometimes not cranking very fast and other times cranking normally - I was wondering if a good starting point for investigation might be to strip out the earths - starter motor to chassis and battery to chassis and clean them all up. Won't do any harm and will at least eliminate the suspicion or prove it to be the fault.

Only bought this old thing for a bit of fun driving it now and again. Spending more time tinkering with it than driving but having had a Land Rover product before I guess I should have known better. Quite enjoying it anyway. Apart from the stink of petrol when I do drive it. Just ordered a new set of tank top gaskets as investigation looks like they are the cause of that.

Try disconnecting the warning light wire from the alternator whilst the ignition is on and the lamp lit. (Should be brown/yellow, but I think mine was white). If the lamp stays on when you've disconnected then you've got a short to earth in the wire between the lamp and alternator where the insulation has chafed through and it's touching bodywork or another chafed wire. It can also be intermittent if the duff wire is moving about.

An easy way to check your earth to starter is to wait until you have the problem and then use a jump lead to connect from negative terminal of battery direct to something close to starter motor. If cranking speed is better investigate where your bad earth is.
You could also have an intermittent fault on the feed side and possibly more than one issue that will lead you up the garden path.

boguing said:

Try disconnecting the warning light wire from the alternator whilst the ignition is on and the lamp lit. (Should be brown/yellow, but I think mine was white). If the lamp stays on when you've disconnected then you've got a short to earth in the wire between the lamp and alternator where the insulation has chafed through and it's touching bodywork or another chafed wire. It can also be intermittent if the duff wire is moving about.

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That’s a good idea, I’ll try that when I get the chance.

barleywine said:

An easy way to check your earth to starter is to wait until you have the problem and then use a jump lead to connect from negative terminal of battery direct to something close to starter motor. If cranking speed is better investigate where your bad earth is.
You could also have an intermittent fault on the feed side and possibly more than one issue that will lead you up the garden path.

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Good idea, was going to try it but it has worked perfectly ever since!