Charging Issues - Still!!!

[YellaBelly]

Had an overcharging issue on the Locost for a wee while now, light stays on dimly when running and gets brighter with revs. goes up to around 15V at 3000rpm off-load so I have been running with lights on to keep it around 14.5V.

Got 2 new regulators yesterday, fitted one just and the fault is still there. tried the other and no change. So can anyone give me some idea as to what the H3ll is worng?
Most P'd off now  

[fullpint]

Don't look at me  I hate electrics..

[paintman]

Don't know if you have a local Lucas Factors near you but I find them really helpful and if you take off the alternator they will check it out for you
and change the diodes if necessary.

[Bulldog Bri]

Check your earths. You could be getting a feedback from something giving a false signal. Bad earths can cause all sorts of strange things to happen. 

[YellaBelly]

Agreed, but I am still getting overcharging shown on both voltmeter and a multimeter, so I reckon it might be the rectifier breaking down?

[Hairy Santa]

there be something wrong there, the light should come on bright when first turned on then go off once started, not get brighter

if its 2 wire  the larger normally brown wire goes from alt to batt the smaller wire goes from alt to the one side of ign light, and tother side goes to ign swith +12v supply

and should work that you have 12v from ign which lights the warning light (eathing through the alt) this inturn induces the alternater so that once it reaches 12 volts it cancels out the warning light   - --- +12v plus +12v = 0volts (bulb out)

as the light is glowing dim when ign turned on it would appear that there is a open circuit within the alt (no earth to make bulb bright) and as you have changed the reg several times it must be further within the alt

I have had this before just cant remember what the heck it was

try putting large jump lead from batt neg to body of alternator, just to verify earth

[YellaBelly]

I was wondering if the fact that it is getting brighter as the voltage goes up that the overcharge was causing the voltage difference across the lamp to be high enough (the other way to what it is supposed to be) to light the lamp. The bulb won't care which side is more +Ve 'cos it's only LEDs where that matters.

The problem is, because the voltmeter and multimeter both back-up the fact that it is giving out too much voltage leads me to believe it is more likely to be internal.

I'll try the earth lead anyhow and then if no joy I'll have to strip the alternator and have a butchers.

Edit:
Just re-read your thread Pete. The bulb is actually lighting up fine when the ignition is turned on, so unlikely to be an earth issue, it is on dimly when the engine is running and gets brighter as the revs rise.

[Hairy Santa]

quite a few alts have there own earthing conection, check if yours have one

not sure as regards leds

has it ever worked properly

[YellaBelly]

Yep, worked fine until about 2 days before the Taunton run. Just decided that it wasn't going to play anymore. I've still got my old one which was playing up in a different way before and that's why I put this new one on. I'm pretty sure that fault was a belt issue as it was pulsing the charging as the belt was slipping slightly at higher revs.

I'll fit the old one with a new regulator and see what happens. if it sorts it then at least I know it's worth stripping the other one down and sorting it.

With regards LEDs, they are basically just a diode and will only work if the +Ve voltage is on the right terminal.

With filament bulbs, as long as there is enough voltage difference between the terminals they will light. It doesn't have to be the rating value either, that's why a 12V car lamp will still light even when the battery is much less than 12V, just not very brightly, and I reckon that's probably what's going on here, +12V on the ignition side of the lamp and a fair bit more on the alternator side. The trouble is, even though the voltmeter only shows around +15V, I need to see what DC voltage is present on the lead from the alternator to the lamp. It also makes a difference if there is an AC component on there too. That could happen if the rectifier is breaking down.

Bloody electrics!!