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Hi All,

I am seeing often voltage above 15 volts in my car. The powerfc hand controller reports above 15 volts most of the time and the apexi pen turbo timer always reports 15.2 15.3 15.4 never usually below 15 volts. I have checked with a friend has has a powerfc r33 and he's is usually around 14.2 volts under the same load.

Some time ago (2years) my battery warning light would stay on. After some investigation buy an autoelec it was found that the alternator was overcharging somehow and needed to be replaced. IT was then replaced with a mitsubishi reco one and all has been well since then, no battery warning light. I am unsure of what voltage the car was seeing / running before then as I don't remember.

What voltage does your car report?

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a resistor would fry lol sorry but you would need a dam large one to get voltage down that far on the alt

any thing up to 14.7 is ok

anything above and well you need to look at why is it so high

if its like 14.8 all the time then tis ok regardless of lights on or off its fine

newer cars these days are asking for more volts so alternators have to keep up with every thing so they charge a little up there' nothing excessive but just so computers and what not dont cut out because of volt drop

the only bad thing is because alternators are at 14.6 volts all the time it doesnt do a battery which has a static charge 0f around 12.8, so its getting over charged thats why batteries dont last as long as they use to older cars have bugger all electrics so the alt never really worked that much

electronics in cars are rated from 8 volts to 16 thats the range roughly but for prolonged overcharging with the computer close to alternator will do damage eventually not to mention globes blowing, cd player doin weird things

but getting back to pauls it could be a simple wires broke to the regulator on the alternator which the regulator uses to sense battery voltage to keep the battery healthy if the wire is broken it will sense the battery voltage to be 0 so it will try and compensate for it ie Overcharge

but also there can be other things in the alt which will cause it to over charge but when that happens the reg blows first then no charging at all

well bugger me dead i didnt know i could babble so much about work related stuff hope this fills in the blanks for any one who wants to read it cheers

You should definitely get it fixed as the alternator on my old Hyundai burnt out after overcharging (over 15 volts) for too long and needed replacing, and that is money spent which could have been avoided. I would think it would be the same story for most cars.

EDIT: Also managed to burn out the indicator repeater thingo, so I needed to spend cash on replacing that too.

Edited by Big Rizza

They alternators regulator is supposed to feed the battery a different charge depending on temperature.

Cooler temperatures require more volts, exactly why you will see a higher voltage after you initially start the car, in my case 14.6-14.8v.

Once warm it 'should' drop to a shade under 14v. Mine is a solid 13.8v.

The regulator is there to 'regulate' the amount of voltage your battery see's. As you increase load through the use of lights, rear demisters etc the regulator adjusts the voltage so that it constantly hangs around what it 'should' be. When these go bung you see under charging or over charging.

Edited by Cubes

thats fine too anything above 13.5 is healthy

im not too sure what you mean by temperature but im certain temperature has nothing to do with it the only thing i can think of is that there are more ancillarys running on a cold start up on a car, plus a starter motor has just taken fair wack of the batterys static charge out of the battery the alternator now has to replenish the battery so on initial start up they alternator will charge at a high voltage and higher Amperage which will charge the battery up smoothly and quickly so it will start again later on well thats what i was taught so hmmm

ok after doing some testing with skybee we found that the alternator is giving out 15.5 volts. unplugged and on the battery car is at 13.5volts and drops slowly. when running the alternator is reading as high as 15.6 volts on normal idle with lights on or off so its very high. will take to a local auto elec tomorrow

If the voltage reg is seperate on these alternators you may be able to just replace that part of it - could possibly be the same as on other units.

Mine gives out 13.8v. 2 years - it should still be good. Take it back to that auto elec - I doubt he would expect it to be faulty after only 2 years!

Edited by benl1981

Good point on the voltage regulator! I changed mine on my Commodore twice, and it was an easy thing to do.

My Skyline runs fine, but it would be interesting to see what this guys Mitsubishi alternator is setup like.

(i'd suggest buying a cheap Nissan/bosch alternator from a wreck to test if all else fails)

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