Alternator fails to Charge Battery

[davidmiles]

Hello all, My Battery keeps going flat, checking the terminals with my multi meter the voltage starts to drop when only charged by normal motoring, so i'm topping up with a battery charger, since the MOT I noticed the white plastic wiring loom (picture 2) had come undone about the time I started getting a flat Battery, but I also inadvertently caught the spare terminal on the solenoid with the end of my spanner (while tightening the oil pipe nut) giving a spark, I wonder if Ive damaged the solenoid unit, could this stop power going back to the battery?[frame][/frame][frame][/frame]

[bmcecosse]

Does the red light come on when you switch on IGN - and does it go out when you start up and rev the engine ? You need a volt meter - tell us the battery volts when the engine is running at decent revs - and again with headlights and heater fan running. Nip up the fan belt first!

[chesney]

If it's starting the car there's unlikely to be a problem with the solenoid.

[LouiseM]

You need a volt meter - tell us the battery volts when the engine is running at decent revs - and again with headlights and heater fan running.

Roy - some more info, plus multi-meter readings, are in this thread: http://www.mmoc.org.uk/viewtopic.php?f= ... start=1395

[davidmiles]

Actually, BMC'S got me thinking, I haven't seen the red ignition light come on, for a while now the lights to the clock have fused somewhere, but it hasn't effected the orange oil pressure switch or the blue main beam dip warning lamp. So could it be just a blown fuse I wonder?

[kennatt]

no fuse on warning light,if its not coming on at all,its a fault with the control unit inside the alternator.

[davidmiles]

right, thank you, so it's a new Alernator, they're about £37 so it won't break the bank, I wonder what made it go, if the white clip wasn't involved, am I going to plug in the new one just to have it burn out again, advice anyone?

[kennatt]

before you buy a new alternator,check the output to confirm its faulty,If you haven't got the equipment take it to a decent motor factor,who supplies batteries, and he should be able to check it for you.It could just be the voltage reg inside ,which is obtainable for about £10 on e bay,and a straight forwards diy swap,so long as you have small enough sockets,to take the end cover and unit off.The rectifier is also about £12,but requires soldering on.I think alternators are a bit more then you quote If you have a look on U Tube there are several vids of how to do both,its not very difficult,too many throw away alternators when they,in the case of the ones on the minor,are easilly reconed.

[Trickydicky]

Just a thought, that alternator looks fairly new, is it still under warranty?

[MarkyB]

No need to replace the whole thing, just the diode pack, worst case is that it will need soldering, often they don't.

[davidmiles]

Gentlemen, you all have Brains the size of Planets, Brilliant, the mention of the ignition light got me thinking, so I traced the fault back to a disconnected ignition warning light wire here in this picture at the bottom of the frame, I went back over my project part three in the Resto thread and about page 61 had this very image, plugged it back in, and hey presto, started up the motor and I was getting 14 volts plus from the battery on tickover. Thats saved me forking out for a new Alternator, thanks to you all. Simple solution in the end to a potentially vexing problem.[frame][/frame]

[lambrettalad]

oh no they will be unbearable now ....................

[bmcecosse]

Heheheheheheheh....well done getting it fixed. Can't say it's 'never' the alternator, because unlikje colis - they don't last 'for ever', but v often there is a simple explanation. I was going to say that the white connector appeared to be for the ignition....

[MarkyB]

Well done, glad it wasn't more serious.
How much tension is there on that wire? It looks awfully taut.