Alan

OK if you can live with it thats OK I guess.

My points were there is no such thing as a 16 ohm lamp - it only seems that way.

Try this to convince yourself. Measure the current on one of these lamps with 1v across it - then with 13.5v across it and calculate the resistance...

And yes I know how the exciter circuit works - Yours isn't getting initiated by the exciter circuit when it should so somethig is up. If your lamps are glowing brightly witth the ignition on and engine not running then your circuit resistance is probably more like 150-200 ohms. What happens when you just disconnect it? same? initiates at higher RPM or not at all

What alternator is this - stock config or something else?

Alternators almost never turn at engine rpm - its almost always faster. But the Porsche stock ratio is not as big as many Detroit set-ups. Even the stock ratio assumes you use the smallest feasible alternator pulleys - when you change the alternator it may come with a bigger pulley as default.

Changing the alternator often leads to non optimal results due to this effective pulley ratio or the alterator minimum rpm characteristics. Going with a smaller alt pulley or larger crank pulley will certainly help (check max alt rpm though too).

I'm not trying to pull your chain - you can really improve this - use a power resistor.

Alan

jwillman

I tested the resistor connected to my alternator voltmeter instrument and got 156 ohms resistance. My warning bulb test okay using a 9 volt battery.

I will order a new risistor from Roger tomorrow. What would this high resistance to do me? is that why I had to rev so high to start the charging?

Thanks

Alan

Yes I think that is probably it ! good work testing it out.

Initiation is quite critical - below a certain point there is insufficient field current to create the required rotor magnetic field and - nothing happens... Higher RPM often helps because intrinsic magnetism in the rotor (esp. on well used rotors) will generate some output that supplements the exciter current from the dash.

Alan

jwillman

I installed the 68 ohn resistor and now appear to have 13.5v on start with no rev'ing. I will continue to monitor. Of course the alternator guage is still reading 11v when i show 13.7 at the battery.

Thats another battle.

Thanks for all the help.

Mrmerlin

you could consider moving the alt needle on the gauge,
hold the shaft then push the needle a bit to reset its position.
This also works well for those that have cant get it full issue on the fuel tank,
and they have already replaced the sender

jwillman

Thanks Stan. Thats brings up a question. I assume the guage should read charing voltage and not battery voltage.

Mrmerlin

the alt gauge will read the output of the alternator