Starting problems, cup alternator conversion related?

[Korky]

Ever since I converted to the cup alternator setup I've had starting problems, replaced the battery and it was fine for a month untill today.
Got in car, wouldn't start but did bump off, checked volts with multi meter, 10.8 when running but if opened throttle rose to 11.8 and rose again when repeated.

I know the cup alternator is 75amp and the ph1 sport is 110, do I have to put the ph1 internals from the alt in the cup housing? Or is this totally unrelated?
Anyone had similar experiences or any advice?

Need it fixed for Saturday as I'm meant to be on the rolling road.

Cheers in advance!

 

[Korky]

Anyone?

 

[Djw John]

Before replacing anything, remove the battery negative, then remove the main cable that goes onto the alternator and sand the surfaces clean, on the alt and the cable. Then connect it all back up and see how it is, you're aiming for around 14.4v

 

[Korky]

Cheers mate, will try this!
Yeh, should be around 14.4 at running?

 

[Djw John]

Yup should be

 

[Korky]

Tried a few things but the battery is charging at 12.8 now, anyone think of anything other than the alternator? It hasn't done many miles!

 

[Djw John]

Is that after sanding those points clean? Have you checked what voltage the alt is running at at the alt itself and not just over the battery terminals. Migt need to clean up the main gearbox to chassis earth as well

 

[MicKPM]

As above, check the voltage output at the back of the alternator and make sure all power consumers are off (lights, heater blower, radio).

Most likely going to be the alternator though.

 

[Korky]

Cheers guys! Made it to the rr day today but I do believe it's alternator now.

 

[Korky]

Just to clarify for anyone with similar problems, it was infancy the alternator.

Cheers for everyone's advice!

 

[Djw John]

Fair enough, best to rule out the simple things first!