Hitchcocks Forum

I can confirm this does not work. Tried a supposedly "non polarised" H4 LED headlight bulb. Lasted less than half a second or extremely intense light. SOmethng akin to a camera flash.



I have it on good authority that positive earth LED taillight bulbs will work on AC but that the stop and tails don't (they work but the whole thing lights up all the time).

Well, at least we should thank you for taking one for the team as our Cousins say, and for saving us the expense and disappointment!



A.

Stinkwheel, I can't say I'm surprised.

The AC regulator only regulates one side of the waveform. It relies on the fact that the alternator is of limited power, and a load which is not far beneath that. My handbook says he AC side is 5.2A at 14V - or 72W. With a 60W bulb it's only regulating 12W. - (OK probably more at higher revs).

Fit a 12W LED bulb and the voltage on the unregulated side will go very high. I would imagine a failing main beam will always take out the main beam warning light too.



My handbook also says the DC side is 14V at 8.5A - or 119W. That's 192W altogether. Not sure I believe it!

Surely the AC regulator is capable of handling the full AC output when the engine is running? Otherwise there wouldn't be an "off" position on the light switch. The alternator is still generating power on both sides when the engine is running.



It's possible that the combined output IS quite high compared to earlier RE India versions, the stator body is a wider (deeper) version of the old stator. The extra width of the stator cores means longer windings, etc.



A.

Adrian, it depends on what you mean by "handling it". In the off position the only thing connected to the ac output is the regulator. It just has to look after itself.

One half of the waveform will go to quite a high voltage but with no current, therefore no dissipation. The other half of the waveform will rise to 17V then collapse to a small voltage (maybe 1V?) but with a high current (maybe 10A) so power dissipated is only around 5W

It won't protect a low load as Stinkwheel has demonstrated.

So what if one were to connect a second AC regulator in series with the existing one but the other way round?

You could try it. I don't think it would work, although I'd be interested to find out.

I think that at low revs it would be fine but at higher revs as it limits on both sides of the waveform the lights would get dimmer. I THINK that the bulb would survive ok.

But it's all theory and no responsibility can be accepted etc.etc. I'd try it with an ordinary bulb first.

Oops - NOT IN SERIES (missed that) there would be no regulation at all. In PARALLEL.