Hey again, 
I'm slowly taking over the 'urgent' forum.
 
Last night 15 minutes into a 30 minute drive home, the car started dying on me. Stereo went first, then boost gauge, then the warning lights all came on.
Voltage was down to about 10.8v
eventually jump started it and drove home.
Today I've been testing various things. I've found out that with no load the alternator charges at about 13.3v @ ~2500rpm.
With the fan on high and high beam it barely gets to 11.9v @ ~2500rpm.
 
The alternator was rebuilt February 2012. The battery was replaced around then too.
I had an oil leak that was caking the alternator in crud, but I've since cleaned the alternator and sorted all that out. Any ideas as to what could be causing this?

Poor ground? perhaps

Have you checked the tension on the alternator belt? Might be loose?
Mine charges 14.8v at idle with no load.

Yikes! That's impressive. Is that the turbo/100 amp alternator?

Checked tension. Fine. Checked/cleaned battery terminals. No difference.

The interesting part is that I pulled the engine out in 2010. It was 18 months later that this happened the first time. It's been 18 months since then as well.

Could just be coincidence. I think I have all the grounds hooked up. Trans, head, LH inspection panel.

Also worth noting. The three pins on the alternator were reading 11.1v, ~11.1-11.6v (can't remember) and 12.1v at idle.

Mines a Gen3 Turbo not sure what the alternator is. I took the reading from the positive and negative terminals on the battery.

Yeah. That would be the 100amp.
I've tested the bridge rectifier and one of the terminals doesn't show continuity. My main reason was replacing the voltage regulator.

failed regualtors are common. we can supply replacement regs or complete alternators.
 
have you checked the ALT fuse??

Thanks for the reply, I need to get this car back on the road asap, so I just got one locally. I tested the bridge rectifier though and it seems that one diode isn't letting current through in either direction. Although I'm happy to replace the  regulator anyway (It was probably dead as a result of the rectifier failing), I now need to sort out the bridge rectifier...
ALT fuse is fine.
 
Does anybody know any details about the bridge rectifier? where to find a replacement, how to fix it, part numbers, what alternatives there are, etc.?

when my alt had similar issues it was the Rectifier.  Most garages will be able to handle an alternator / rectifier recondition.
 
or if you can remove it yourself then take it to an auto elec you should save some cash. (NB it's a pain to remove tho)