No alternator light

Post by **want33s** » Sun Nov 23, 2008 9:40 am

The alternator light in my Zook doesn't work anymore.
I fitted a 100A EF Falcon alt 12 months ago and its been great until now.

If I start the car and then disconnect the battery it dies, but if I start it and give it a rev it will idle with batt disconnected.

The light doesn't come on with ignition or when engine is stopping with ignition off.
I have checked the bulb.. It's fine.
I have powered the wire to the bulb and it works.
Voltage at battery is 12.6V and at alt is 12.2V before a rev and 14.5V after.

Alt is charging but why does it need a rev to start working and why doesn't the charge light work?
Could it be a problem inside the alt or should I be looking harder at the wiring?

Jas.

Post by **presto** » Sun Nov 23, 2008 4:11 pm

the alternator needs the warning light to work to start charging, if your warning light doesnt work then it cannot create a field to start charging and it has to self excite - hence needing to rev it to start charging. disconnect the plug from back of alternator and probe it with a test light, it should bring the warning light on on the dash. if it does then it sounds like your reg is faulty, if the light doesnt come on when you probe it then the problem is in either the wiring or the instrument cluster.

Post by **presto** » Sun Nov 23, 2008 4:12 pm

have you checked the fuses?

Post by **want33s** » Sun Nov 23, 2008 4:24 pm

presto wrote:have you checked the fuses?

Yes all fuses are good. Visual & continuity.
I'll try probing the plug.
Cheers..
Jas.

Post by **presto** » Sun Nov 23, 2008 4:43 pm

I have powered the wire to the bulb and it works

the warning light has power supplied to it from ignition, and gets an earth thru the alternator to bring the light on and produces an output back up that wire to turn the light off when charging.
did you supply power to the alternator side of the bulb or the ignition side?
sounds like the alternators probably fine and you've lost your ignition feed somewhere. [/quote]

Post by **84ZOOKSTA** » Sun Nov 23, 2008 6:20 pm

The alternator needs 12V to excite it. These ford alternators will self excite when reved if that 12v is not there.

Check there is +12v on the Ignition wire at the alternator.
If there is there could be a fault with the regulator.

Cheers

Post by **want33s** » Sun Nov 23, 2008 6:26 pm

I just tried the test light on the two wires out of the alt.
One did nothing, the other made the light come on.
What does this mean?

Post by **presto** » Sun Nov 23, 2008 6:29 pm

you missing an ignition feed. should be an L and S pin, L is warning light and S is battery sense (ignition feed). did you have power on both or only the one that made the warning light come on?
double check the fuses

Post by **want33s** » Sun Nov 23, 2008 6:34 pm

presto wrote:you missing an ignition feed. should be an L and S pin, L is warning light and S is battery sense (ignition feed). did you have power on both or only the one that made the warning light come on?
double check the fuses

I'll do that in the morning and get back to you.. cheers again..

Jas.

Post by **presto** » Sun Nov 23, 2008 6:38 pm

hangon i might have misread... did you mean one made the warning light come on or it made the test light light up?
the test light should light up on both pins, and one should bring the warning light on the dash on. if the test light is lighting up and the dash light isnt coming on then thats your ignition feed. the other pin is the warning light circuit.

Post by **want33s** » Sun Nov 23, 2008 8:01 pm

presto wrote:hangon i might have misread... did you mean one made the warning light come on or it made the test light light up?
the test light should light up on both pins, and one should bring the warning light on the dash on. if the test light is lighting up and the dash light isnt coming on then thats your ignition feed. the other pin is the warning light circuit.

One made the test light glow. the other made the dash light come on but not the test light.

Post by **presto** » Sun Nov 23, 2008 8:58 pm

sounds like a faulty reg then, the test light didnt light up on the warning light pin because its a higher wattage globe. best off taking it to an auto elec and get them to do an overhaul to check everything else in there and replace the bearings.. might even be cheaper to get an exchange unit. try get a bosche if you can.

Post by **want33s** » Mon Nov 24, 2008 2:00 pm

presto wrote:did you have power on both or only the one that made the warning light come on?

The test light came on in pin 1 it also reads 12V. The other pin makes the dash light come on but reads 0V.

Jas.

Post by **presto** » Mon Nov 24, 2008 2:03 pm

if one is lighting up the test light and the other one is bringing the warning light on the dash on, then the wiring i fine and the fault is in the alternator.

Post by **want33s** » Mon Nov 24, 2008 3:48 pm

presto wrote:if one is lighting up the test light and the other one is bringing the warning light on the dash on, then the wiring i fine and the fault is in the alternator.

Cool.. thanks heaps for the help Presto

I have found another alt.. Just hope it gets here before the weekend.
Jas

Post by **want33s** » Thu Nov 27, 2008 4:19 pm

Fitted a replacement alt today. All good now

Jas

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