BATTERY/ALTERNATOR LIGHT IS FLASHING! help!

[Paddy_g46]

this started last night after i went around a corner quite sharp (not sure if this has anything to do with it?) anyway now when im driving it is constantly flashing untill i let the car sit at idle then it seems to go away but not always??? i checked the voltage on the battery and its at 12.4v when engine off and 12.4v when on so its not charging! alternator is only 3 months old though!!! any1 got any ideas what to check?
oh and also at first i thought my earth strap to the body was bad so when i checked it, it sanpped off in my hands, but i have just fitted a new 1 and i still have the problem!

 

[Paddy_g46]

i just found this plug type thing hanging around next to the alternator? should it be plugged in somewhere?

 

[Paddy_g46]

i just checked the voltage across the b+ on the alternator and the negative of the battery and got 12.5v again, also there is no cable connected to b- terminal on the alternator???

oh and i found where that yellow plug goes and i put it back but it didnt seem 2 do much?

 

[Paddy_g46]

HELP!!!

 

[Jay Payne]

Do you know how to volt drop the cables?

 

[Jesske]

Only 1 cable (red on mine) is connected, that's true.
That plastic thing also isn't connected in my 182

 

[Paddy_g46]

Do you know how to volt drop the cables?

:S

 

[Dink]

sounds like you have no supply to the field magnet of the alternator to me

 

[Paddy_g46]

sounds like you have no supply to the field magnet of the alternator to me

i see your an electrician aswell lol, i have checked the feed terminal and it is reading 12.5 volts

 

[Dink]

feed or field?

 

[Paddy_g46]

feed or field?

feed

 

[Jay Payne]

Ok quick auto electrics lesson.
car running
1, connect a volt meter (set on volts) from battery positive to alternator output wire B+..... you should see 0 volts if you see anything higher than 0.5 volts you have bad connection between the battery and alternator

2, connect a volt meter (set on volts) from battery negative to the body of the alternator. (earth) ....you should see 0 volts if u see anything higher than 0.5 volts you have bad connection on engine/alternator earth (negative)

the process is called volt drop, basicly any voltage that cannot travel down the cables due to poor connections will travel through the volt meter and show as a reading. Great test, so simple and not very well known. I use this method of testing everyday at work.

The other thing you can check is the small wire on the alternator (sometimes blue) disconnect it from the alternator, ignition on, battery lamp should be off, if its on you have a short to earth between the alternator and dash.

Then touch it against something metal eg. alternator casing and get a mate to look at the light. it should be on. if so all is well.

Alternator faults are really quick and simple to diagnose if you know how

Hope this helps, if not pm me

 

[Paddy_g46]

Ok quick auto electrics lesson.
car running
1, connect a volt meter (set on volts) from battery positive to alternator output wire B+..... you should see 0 volts if you see anything higher than 0.5 volts you have bad connection between the battery and alternator

2, connect a volt meter (set on volts) from battery negative to the body of the alternator. (earth) ....you should see 0 volts if u see anything higher than 0.5 volts you have bad connection on engine/alternator earth (negative)

the process is called volt drop, basicly any voltage that cannot travel down the cables due to poor connections will travel through the volt meter and show as a reading. Great test, so simple and not very well known. I use this method of testing everyday at work.

The other thing you can check is the small wire on the alternator (sometimes blue) disconnect it from the alternator, ignition on, battery lamp should be off, if its on you have a short to earth between the alternator and dash.

Then touch it against something metal eg. alternator casing and get a mate to look at the light. it should be on. if so all is well.

Alternator faults are really quick and simple to diagnose if you know how

Hope this helps, if not pm me

thanks alot mate ill give this a go 2morow, ill let u know how i get on

 

[Paddy_g46]

but how would you explain me only getting 12.5 volts on the battery with the engine running?

 

[Jay Payne]

but how would you explain me only getting 12.5 volts on the battery with the engine running?

Battery voltage = 12.5v ish, charging voltage 13v - 14.5v if u have a poor connection somewhere loosing you 1 or 2 volts that would explain it. Do the tests tomorrow to confirm that all the wiring is good, must be done with the engine running. Oh and forgot to mention make sure you connect the meter to the terminal posts on battery and alterntor, not the terminal themselves

 

[Dink]

but how would you explain me only getting 12.5 volts on the battery with the engine running?

if you have no field magnet in the alt it won't create a charge

 

[Paddy_g46]

if the alternator was not charging at all would i have less then 12.5v when engine is on?

 

[Jay Payne]

if the alternator was not charging at all would i have less then 12.5v when engine is on?

NO you would read battery voltage whatever that is, obviously this would go down as the battery went flat

 

[Paddy_g46]

ANY IDEA HOW LONG IT WOULD LAST? DO U THINK THERE IS A CHANCE THAT IT IS CHARGING BUT AS U SAY JUST LOOSING A FEW VOLTS?

 

[Paddy_g46]

Ok quick auto electrics lesson.
car running
1, connect a volt meter (set on volts) from battery positive to alternator output wire B+..... you should see 0 volts if you see anything higher than 0.5 volts you have bad connection between the battery and alternator

2, connect a volt meter (set on volts) from battery negative to the body of the alternator. (earth) ....you should see 0 volts if u see anything higher than 0.5 volts you have bad connection on engine/alternator earth (negative)

the process is called volt drop, basicly any voltage that cannot travel down the cables due to poor connections will travel through the volt meter and show as a reading. Great test, so simple and not very well known. I use this method of testing everyday at work.

The other thing you can check is the small wire on the alternator (sometimes blue) disconnect it from the alternator, ignition on, battery lamp should be off, if its on you have a short to earth between the alternator and dash.

Then touch it against something metal eg. alternator casing and get a mate to look at the light. it should be on. if so all is well.

Alternator faults are really quick and simple to diagnose if you know how

Hope this helps, if not pm me

mate i just tried your tests, for the first 2 i got 0v so that is fine then i disconnected the small wire with the ignition on, which made the battery light go out as it should, but then when i touched it to earth the light on the dash stayed off? so what does that tell you? also i just connected my volt meter to the battery and secured it to the wipers and went for a drive, when driving the volts go up to 13.5v and if i rev it up to 5k revs i get 13.9v, any more ideas? also the battery ligth didnt flicker for a good while but then on my way home it started to flicker again once id taken off the meter. im really baffled!

 

[ditz]

the small wire is the exciter wire ! starts the alternator charging at low revs and also is the signal for the light

 

[benji&eka]

faulty alternator imo. or slipping belt if you've just fitted an alternator recently check the basics

 

[benji&eka]

the small wire is the exciter wire ! starts the alternator charging at low revs and also is the signal for the light

i thought it was just the id wire for the light and nothing to do with starting charging, i thought the alternator charged without being switched on as such
(but then again i'm NOT an electrician just a lowly diesel fitter LOL)

 

[Jay Payne]

the small wire is the exciter wire ! starts the alternator charging at low revs and also is the signal for the light

i thought it was just the id wire for the light and nothing to do with starting charging, i thought the alternator charged without being switched on as such
(but then again i'm NOT an electrician just a lowly diesel fitter LOL)

ditz is right it does need a feed to get it started

 

[benji&eka]

ok
is that ign feed then and how does it work the light.?

 

[Jay Payne]

ok
is that ign feed then and how does it work the light.?

The bulb on the dash has an ignition feed at one side and the other side goes to the alternator. With the ignition on you should see a voltage at this wire when disconnected from the alternator.

When its connected to the alternator it has a path to earth and the light comes on. as soon as the alternator starts to charge it outputs a vlotage on this wire, so now the bulb has a live feed at both side of it and gos out(as it has no earth path) if the alternator stops charging(broken belt or something) the path to earth will be returned and the lamp will come on again.

Patrick, we have eliminated the main cables and after you refitted every thing it seems to be charging. 13.5v - 13.9v. It is a problem that the light didnt come on when you earthed the wire. Was the ignition onn and did you have a good contact to bare metal? If your not sure use a peice of wire to connect it to the battery -tive. again getting a friend to keep an eye on the dash makes it much easier.

If your sure you did the test correctly then you either have a dodgy bulb connection/printed circuit, or a problemwith that wire. As mentioned above check there is a feed there with ignition on and wire disconnected.

 

[benji&eka]

aah.. cheers i'll remember that. gonna piss off our resident sparky with that one at the earliest opportunity 'cos he thinks we are just a bunch of spanner monkeys

 

[Paddy_g46]

now it is doing it randomly whilst driving, but if u dip the clutch adn let the engine idle it stops flashing! also should it even flash? i thought it was meant to be a continuous light???

 

[Jay Payne]

Either you have a problem with that wire or something wrong with the alternator. is it a regular flash or random flickering?