Red light on with alternator

[rogerowen]

My daughter's 1960 948 has an alternator (fitted by previous owner). The car has been switched to negative earth. At tick-over the ignition light is full on and does not extinguish much below 1000 RPM. A marine engineer friend wondered if the pulley was too small, but I'm guessing it is the one that came with the alternator. Does anyone know if there is any kind of adjustment?

[bmcecosse]

Oh dear -wrong way round...the small pulley is fitted to an alternator precisely to MAKE it charge at idle speed. I was going to ask if perhaps the alternator had been fitted with the large dynamo pulley - which would explain no charge at idle. As long as it does charge above idle speed - I wouldn't worry about it. On my own car - when first started - the engine needs to be revved slightly to make the alternator kick in - but then it charges away merrily. This is where the ammeter pays dividends. Can see what's going on!

[linearaudio]

Worth checking the warning light wattage, as this has a significant effect on the "cut-in" speed. For example, dumper trucks and the like will often have a resistor wired across the warning light to lower its effective resistance as those old single pot diesels probably don't get much over 1000rpm flat out!!
A 1.1watt bulb works fine on my moggy, extinguishes at about 600-700rpm at a guess!

[bmcecosse]

My alternator works perfectly well with the red light disconnected......... I don't see it has any effect on cut in speed. But I accept this may not be true for all models. Mine is an 18 ACR.

[linearaudio]

My alternator works perfectly well with the red light disconnected......... I don't see it has any effect on cut in speed. But I accept this may not be true for all models. Mine is an 18 ACR.

As has bin noticed on a similar thread, you seem to have a unique 18acr, as every other one in existence needs an "exciter" voltage on the little terminal, along with alternators generally.
Or maybe the mere excitement of being in a rally bred vehicle with state of the art brakes etc is enough to make it spring to life!

[bmcecosse]

I guess so - but do try it - pull the little wire off and see what happens. Mine works just fine like that - balances loads etc perfectly well.

[MarkyB]

Didn't you say that you have to rev the engine to get it charging?

[bmcecosse]

Initially - from the cold start in the morning. Not lots of revs - just a touch. Does that whether light is connected or not.

[rogerowen]

Thanks all, looks like it's nothing to worry too much about - just a bit irritating. The car has an amp-meter and it's not showing a massive discharge at tick over. Interesting point about the revving to get the alternator to kick in - I had a Ford Cargo Horse lorry that did exactly the same (although I've never come across that before or since).