Hi all,just bought a new battery and alternator on car but batt still going flat,ive checked the wires bolted on the alternator and the fan belt is brand new and at the right tension.Just wondering if anyone can post up wiring diagrams or have more info on this please.The car is a cinq sporting

hi mate first thing to do if you have no tools to test disconnect the battery overnight thiw will tell you if the battery is holding( i have had dead new batteries so dont think as its new it must be ok)then some people will tell you not to but start the car and disconnect the red positive lead. if the alternator is working (and providing the red from the alternator is soldered into the + battery terminal)the car will still run it if the alternator is charging something. it should work the lights aswell.if the car stops immediatly then i think the altenator is duff. if all is well you must have a battery drain like a boot light radio or alarm.most good battery centres will test the car for free and probably point you to the culprit.

Does the battery light come on when you turn on the ignition (before starting car)?

Cheers

D

No thats what i was wondering the batt symbol on dash doesnt apper anymore and the batt is fully charged as i charged it all day yesterday.

you have pm!!

Cheers

D

hi, having exactly same issue, Seicento Sporting, no battery light on start up or at all, and all power just drains away?

Any help would be greatly appreciated

Steve

You need the 12V supply on the wee wire. Check it..

Cheers

D

rallycinq said:

You need the 12V supply on the wee wire. Check it..

Click to expand...

Not saying it is that, but you'd not be the first to replace an alternator when only the little feedback wire was at fault.

what wee wire, sorry im not great with electronics! is it on the battery or alternator?

Alternator -- or, rather, to the alternator. Usually it has a small spade connector on the end.

fingers99 said:

Not saying it is that, but you'd not be the first to replace an alternator when only the little feedback wire was at fault.

Click to expand...

where would this wire be/ go to?

To the alternator -- usually there's a small lucar/spade fitting on the end.

thanks, ill check it out in the morning!

another thing worth mentioning...
if the alternator warning bulb is blown, then the alternator will not charge the battery.

the reason being that alternators don't contain any magnets and so require the few miliamps that flow through the bulb the make a small magnetic field around the windings which kicks it into life once the alternator starts spinning and sustaining its own magnetic flux

so... if the small live feed is connected but you still don't get an light on the dash. it is worth checking the bulb.

(its "common" for people to fit leds in the dash but if they replace the alternator bulb with an led then usually the alternator stops charging)

hi, no luck with the small wire, i dont know which bulb you mean, the dash one, im still not getting a light to even reconising the existance of a battery? car wouldnt start so i jumped it and it went off ok, tho its not charging or holding any charge?

Could it be the alternator? - is there an easy check?

You need to find the small signal wire for the alternator. If its not there and not producing a 12V 'tickle' the alternator won't work.

Cheers

D

Do all the above, then check the alternator (alternators are expensive, bulbs and missing wires are not).

Alternator should put out about 14.5 volts across the battery terminals at idle. Do, do, check the rest first! (Idleitis can cost you pounds!)

My guess is regulator.

Once the alternator is rotating it produces it's own voltage to the rotor field windings via brushes and slip rings.
This is also controlled by the regulator that varies the current in the stator windings to sustain the voltage.

Alternator problems are mostly due to the regulator pack failing.
Corrosion to the welded terminals could be a problem if you look at the design, But a continuously demanding system will put strain on it also.

The wire that goes to the indicator lamp lights up when the engine is not running because the current passes through the brushes and field windings.
When the engine is running and the alternator is working correctly, The voltage potential is the same across the lamp so no current will flow to light it.
This wire is for indication only.

However, If you have electric power steering, The power steering ecu will detect a fault on the alternator and shut off control.

all above is right other then the wire/bulb been indication only. the windings need a small current to START them working. once its spinning it sustains its own magnetic feild

Bugger!
Forgot that the regulator needs initialising.:bang: