Intermittant alternator output:

150K '93 22RE 2wd, everything stock except recently installed ENGNBLDR timing chain and head gasket kits.
Works great (thanks, ENGNBLDR <img src="/forums/images/graemlins/kewl.gif" alt="" />) except:
On most engine starts, two dash lights come on: "Battery/Alternator" and "Brake". Sometimes these lights go out on their own, sometimes not.

When these lights are on, the voltage gauge also drops down -- pretty good indication that charging is not happening.
Also, garage automatic battery charger indicates that battery is becoming discharged when running for extended periods of time with dash lights on.

Engine runs fine whether charging or not, and I can't find any loose wiring connectors.

Any suggestions? When alternators fail, can they be intermittant like this?

Thanks in advance,
Ed