Hi Everyone,

 I bought a 2000 1.4 MPI with 66k on the clock a couple of months ago. I drove it around for a few days, then as the MOT ran out i parked it in my front garden. A few days ago i decided to get the car to a garage for a MOT. it had only done 900 miles since the last MOT, so was pretty confident it would pass. I tried to start it, it was completely dead, not even a glimmer of a dashboard light. I put it on charge overnight, and tried it again next morning, still totally dead. I then got another car to jump start it, it started no problem, I then removed the jump lead and it instantly stopped. I started it again, everything worked, lights, wipers, windows etc. Then once again when i removed the jump lead, it stopped instantly. I bought another battery, put it on, and the car started, everything worked, but the battery light was now on. i charged the battery overnight to top it up, went for a MOT and it passed, but the light is on and the battery is not charging. I found two pairs of wires, that were hanging down between the battery and the alternator, and thought that must be the problem, but, on closer inspection, the one coming out from the lower loom is brown with a stripe of black, the other is  green/black,( possibly more black than green)  the other pair that comes from the loom under the battery is brown ( just brown) and the other green with a fine black stripe. i have been all over the net for a colour code wiring diagram, but could only find one that has a virus type thing, so didn't down load it. So, anyone able to confirm what the wires may be please, I thought they may be different because a plug had been ripped of or something..? Also, the old battery was completely dead, i tried to charge it overnight on a bench so it was not connected to a car, but it didn't take any charge, and if you short it, it gives a very feeble tiny spark. So, why did it die when it was not being used.? I put a meter on it, it had 10 volts. any ideas please.

Thank you, sorry its long, but I thought I would give you the full story.

regards, Alf. 

@aldthephoneman - Well, if the battery light works, then the load sense wires are connected. Can you test the health of the alternator?

The brown/black and green/black broken wires you've found are responsible for the control of the air conditioning, so won't be relevant to your battery/charging issue.  The one you should look for is blue, on a nearby two-pin connector (the other wire may also be broken - brown/red one side of the connector, purple/green on the other).  I guess that when you turn the ignition on, you don't see the battery light come on (before you turn the key further to start the engine)?

Edited 16 April, 20188 yr by Wino

@Wino - IME if the control wire(s) are broken you don't get a battery light at all.

17 hours ago, aldthephoneman said:

Also, the old battery was completely dead, i tried to charge it overnight on a bench so it was not connected to a car, but it didn't take any charge, and if you short it, it gives a very feeble tiny spark. So, why did it die when it was not being used.? I put a meter on it, it had 10 volts. any ideas please.

The old battery died because it was, well, old and dying. It is a typical scenario of how a battery dies. Last night or two days ago the car started, today it is dead. Moreover, the charging system has issues. A 10 Volts on that battery means one element is shorted.

Word of advice: if you keep driving the car with issues on charging system, you risk shorting the life of the new battery.

40 minutes ago, KenONeill said:

@Wino - IME if the control wire(s) are broken you don't get a battery light at all.

 

And is your experience of this platform?

The battery light is driven by a microcontroller in the instrument cluster; it doesn't form part of a 'simple' circuit such as used to be the case with alternator excitation. Let's allow the OP to tell us what he sees at ignition on, meanwhile I'll try an experiment later/tomorrow on my car to see if I can get battery light on with engine running, and no signal connection to the alternator (i.e. no charging, if the residual magnetic fields have died sufficiently since last used last night)? The car's brain has other sources of information about battery voltage / charging situation, such as the dedicated wire that goes from fuse 10 on the battery fusebox to the Onboard Supply Control unit.

Thanks for all your input. the battery light is on all the time once you switch the ignition on, and stays on, doesn't even flicker.  I looked for any broken wires or disconnected plugs, but found nothing. I will take the battery off and remove the battery support base next, as there is a lot of wires going under the battery then disappear, and, when i removed the old battery, after taking the two terminal connectors off, it was hard to lift out, I put some pressure on it and  then it suddenly just lifted, so I wonder if I have snapped a wire but cannot see it ? Once again, thanks for your input, most helpful.

Alf.

Check fuse 10 on the battery fuseholder (under a cover, to the right of the strip fuses as you look from the front into the bay).