Battery/Alternator problem

[Steevo]

I've only driven my 5 twice, and both times the battery has drained to no output at all, I can charge the battery in full and leave it for a week and it does not discharge at all, but after driving it 10 miles to the bodyshop it's totally dead again, almost like the alternator is not charging it at all, so it's gone from full charge, to ten minutes later, dead as a door nail. Incidently the alternator is brand new, as is starter motor (if that makes a difference) Any ideas please? :)

[mk5gtt]

The problem might be the wires on the alternator might not have the live feed to charge the battery have had this problem before and put a switch with a feed to the alt to start charging works fine now

[royz]

have a look at the 2 small wires at the top of the alternator. the one closest to the engine if snapped will cause it to not charge. have a check for any broken wires dose the battery light come on.

[Steevo]

have a look at the 2 small wires at the top of the alternator. the one closest to the engine if snapped will cause it to not charge. have a check for any broken wires dose the battery light come on.


Well, the wiring to the alternator looks fairly new and all looks to be rewired after rebuild etc (before i bought the car). No battery light has come on whilst driving and there has been no erratic clocks or electrics either :scratch:

[J$£5GTT]

duff battery!?

[Steevo]

duff battery!?

Well yeah, it very well could be, but the battery is definately holding charge long term unless it's being driven though, and the battery test is inconclusive by just saying 'recharge and retest' :crap:

[Eugein Offord]

it could be the above.. but ive had the same with a battery... the problem was that the live feed to the starter motor that runs from the bat and over the top of the gearbox had chafed at the starter side onto some mount at the rear lower section of the block and as i drove it was shorting out.. a quick look and wiggle at the big red wire .. pulling it from behind the rear of the front wheel will tell you straight away..............:)only takes a second

[Nick k]

it could be the above.. but ive had the same with a battery... the problem was that the live feed to the starter motor that runs from the bat and over the top of the gearbox had chafed at the starter side onto some mount at the rear lower section of the block and as i drove it was shorting out.. a quick look and wiggle at the big red wire .. pulling it from behind the rear of the front wheel will tell you straight away..............:)only takes a second

Regarding the 2 wires that go to the top of the alternator, the yellow is closest to the engine and purple to the rad. Have you got a volt meter? Another way to check its charging is to put lights, heater on,wipers etc to load the battery circuit whilst the engine is running then pull the yellow wire off the alternator, you will hear the engine rpm rise slightly if it is charging as the alternator load is taken off the engine. If nothing changes when the wire is removed and re connected then the alternator is not charging,possible problems are the alternator is fu£#ed or there is no 12 volts on the yellow wire when you turn the ignition on, which the alternator needs to tell it to charge.

[Nick k]

another quick one, you say its had a new starter motor, you might wanna check that both wires have been reconnected back to the starter motor?! One goes straight to the battery and the other around past the gear box to alternator. Could be a school boy error ;)

[Steevo]

That's really useful info chaps, thanks a lot :)