Battery/Alternator query

Kitch · Post by **Kitch** » Sat Jan 20, 2007 10:40 am

Quick Q for ya

Went to the 16v this morning and the battery was dead. Instruments lit up but didn't even make an effort to turn over.
It started fine on Tuesday night.

The car doesn't get driven at all right now, just started and stopped on the driveway.

So I jumped it, and got it running. Once it was running, I put the window down and as it was doing so it cut out. Battery dead again.

So I started to wonder about the alternator. I jumped it again and once running disconnected the positive on the battery and it cut out right away.

Am I right in thinking if I do that, it should keep running due to the alternator? It has on previous vehicles.

Thing is its quite a new alternator. Can't be more than a year or two old!

Any thoughts?

Kitch · Post by **Kitch** » Sat Jan 20, 2007 10:49 am

Also, I recently chipped the ECU....could that do anything to the electrics that would cause this?

Stewart (oily!) · Post by **Stewart (oily!)** » Sat Jan 20, 2007 11:22 am

Sounds like you have beaten the charging system, it will not run with the battery disconnected (current needed to energise electro-magnets in the alterator, danger of killing diodes too, do not do this) batttery is flat, charge it, with engine off voltage across battery should be in the regoin of 12.5 volts, start it up, battery voltage should rise to 14.5 or similar, note battery symbol lamp on dash should go out when engine starts and be on when engine off/ignition on, you may have something draining the battery, ie bootlight on all the time.
Stewart

Post by **docchevron** » Sat Jan 20, 2007 11:58 am

Amen to that. The car cannot run with the battery disconnected.

Charge / change battery, problem sorted, assuming the alternator is doing it's stuff. Are you in later, I'll be passing with the bandit! Speaking of which, I'd best bu&&er off up the M4 and meet him!

Cheers
Chris G

Kitch · Post by **Kitch** » Sat Jan 20, 2007 12:47 pm

I am in later mate, yes.

I have to say, I've run quite a few cars without batterys. The estate did 20miles or so without one. We jumped it using the terminals linked to another car and then Si drove it home. He was so paranoid about stalling it that he forgot himself and switched it off at a petrol station

But anyway....the battery is roughly at 8v and draining. However the alternator readings are all over the place. First time it was 13v, second time it was 5.5v and last I checked 8v!

I don't get how I could have done this personally. Only thing is, it may have been like it for some time seeing as it never gets driven. It runs souly off the battery by the look of it.

Kitch · Post by **Kitch** » Sat Jan 20, 2007 1:48 pm

Some complete legend on 205 GTi drivers just popped up with an idea to this problem. He said to check if the battery ignition symbol is showing on the instruments. If its not, that stops the alternator charging due to a faulty connection.

I'm waiting to see where this is, but sounds promising!

Stewart (oily!) · Post by **Stewart (oily!)** » Sat Jan 20, 2007 2:14 pm

Running without a battery

whatever next, if your voltages are all over the place then its likeley you have killed the alternator (by running it without the battery connected)
Stewart

Kitch · Post by **Kitch** » Sat Jan 20, 2007 2:17 pm

No, that wasn't on this car. It was on the estate and Si's Activa.

This has never been run without a battery.

Stewart (oily!) · Post by **Stewart (oily!)** » Sat Jan 20, 2007 2:26 pm

Are you getting the battery warning lamp on with the engine off? does it go out when the engine starts and maybe is revved a little? (Its the one with a picture of a battery on it in the central set of warning lamps, can you charge the battery off the car? a good overnight trickle charge might sort it, boost positions on battery chargers can really bugger things up.
Stewart

Kitch · Post by **Kitch** » Sat Jan 20, 2007 2:29 pm

No mate, thats what I just said a few posts up

Apparently if theres no lamp theres no charge. So I need to find out why I have no lamp.

I'll pop the battery on charge anyway I think.

Stewart (oily!) · Post by **Stewart (oily!)** » Sat Jan 20, 2007 2:45 pm

If you run a "hot" live wire from battery+ to the small tag on the rear of the alternator then start the engine you should force it to charge, if it does and shows 14 volts at the battery with the engine running then you may have a wiring fault elsewhere in the charging circuit, even the warning bulb blowing will disable the circuit as the bulb is part of the circuit, a mates BX stopped charging a while back and it was that bulb holder

Stewart

Kitch · Post by **Kitch** » Sat Jan 20, 2007 3:04 pm

Ah right, I'll try that. Thanks for the tip off mate!

tom · Post by **tom** » Sat Jan 20, 2007 4:40 pm

If the battery is down to 8Volts it is shagged. No argument. It will probably be killing the alternator as well if you do not change it but the alternator will not be the thing that killed the battery in the first place.

thanuttiscotsman · Post by **thanuttiscotsman** » Sat Jan 20, 2007 6:40 pm

hi folks,
tis right you can drive cars without batterys as the alternator will power stuff!! you dont even need one in to start it if you have another car and leads!! but yeah if when running the engine it cuts out when you dissconnect the battery then the alternator is fecked.!!

rossco

tim leech · Post by **tim leech** » Sat Jan 20, 2007 8:11 pm

My battery light doesnt work either yet it doesnt seem to drain the battery much unless i leave it for weeks.