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Alternator over charging


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I would really appreciate some advice. I have a tdi 300 The alternator showed it was overcharging about 16V I replaced the brush unit on the back of alternator. No change. Then changed Alternator still no change. To keep voltage down switched on lights, fan and spots. Then the lights went out and I am left with only park lights. No emergency flashers or indicators either. The brights work if you switch on the parks and hold the brights on the leaver. What could the fault be?

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16V between where and where?

My guess is poor earth to battery, or maybe live to battery terminal.

'Then the lights went out' - have the bulbs blown because you were sending 16V to them?

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I have a volt meter and I think it measures what is going to the battery or coming from the alternator. I don't think the bulbs are gone as when you hold the leaver back as if to flash brights they work. But the light switch if you switch it all the way on, no lights work not even the parks. I have a duel battery system with change over switch for using one or the other as you need. This has been working for quite a long time like this but this is all a new thing

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This is probably related to the other thread you have going. As FF says the bulbs have blown or if you're lucky all the headlight fuses have gone instead.

Also check that the brown / yellow wire on the alternator gives 12V when the ignition is on, and it is connected up properly. Do you have a any other wires at the alternator other than a thick brown one and a thin brown / yellow one?

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When you are reading 16v, where is this from ?

Put the negative probe on the alternator casing and the positive probe onto the big wire coming out of it as this'll show you what it's putting out.

What voltage is your battery with the engine off ?

You sure it's a 12v alt and not a 24v unit ?

An alt will charge at a higher voltage if the regulator is buggered, however you say you've changed it...... :blink:

HTH

Gordon

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Voltage at batt with engine off is 12.35V. On Alternator only the 2 wires. Something I did notice however was every time with engine off if you put the indicators on some of the other gauges jump. I have once before had a problem with the hazard switch and had that changed. then recently it played up again and it seed as if the multiplug was not quite connecting. I tested the alternator across the battery both off and running. With the replacemet alternator and revs up to about 3000 it was charging at 14.3V

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Voltage at batt with engine off is 12.35V. On Alternator only the 2 wires. Something I did notice however was every time with engine off if you put the indicators on some of the other gauges jump. I have once before had a problem with the hazard switch and had that changed. then recently it played up again and it seed as if the multiplug was not quite connecting. I tested the alternator across the battery both off and running. With the replacemet alternator and revs up to about 3000 it was charging at 14.3V

The voltages are all pretty much perfect.

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going to hijack this a bit.

i'm 12.34V (not running) and 14.16V (running).

Put everything on like fan and main beam and get 14.04V (running).

Does that sound OK ? Considering I just fitted a 100amp alternator.

Thanks

ps battery is a Lucas 4 supreme 650Amp 30 second crank with 68Ah, 4A bench charge.

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Does that sound OK ? Considering I just fitted a 100amp alternator.

Any battery reading over 12V just standing is OK. 14 to 14.4V is a typical output for an alternator, and to only lose 0.12V at high load is just resistive wiring loses at work.

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Just got a bit of advice, What's it worth? On the defender at the back of the chassis the loom seems to come over the corners of the chassis and often the electrical short on the lights and an array of other electrical problems could come from being rubber through. Any thoughts?

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Just got a bit of advice, What's it worth? On the defender at the back of the chassis the loom seems to come over the corners of the chassis and often the electrical short on the lights and an array of other electrical problems could come from being rubber through. Any thoughts?

Examine each wire for bared internal strands & repair as required.

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