sorry I am just now getting back to you I went outta town last night. sounds like a voltage regulator, which on this car is built into the altenator. where did you have it checked ?
the only other thing I can think of to tell you to check would be battery connection these side post batteries in these cars are bad about leaking acid and causing a poor connection that will sometimes make the car do crazy stuff but still have good enough connection to crank and run car. Also check the wire connection going from battery to the altenator. do you know if this is the original altenator ? also how many miles are on this van ?
well I do not know what else to tell you if your battery and altenator test good, other than it may just be a cheap quality altenator and its testing good but is on its way to going bad. sorry I can't guide you any further, but as of now I would say i agree with your husband on the altenator theory. Hope I have helped some what.
well I finally found something that relates to your problem hope this helps this is a GM bulletin (common problem)
ConditionSome customers may comment that the interior and/or the exterior lamps vary in intensity (flicker).CorrectionReplace the voltage regulator attaching screw with the screw and washer from the service kit following the procedure outlined below.Disconnect the battery cable. Remove the wiper module cover (U-Van). Remove the voltage regulator ground screw (1). (This is the recessed screw located 1/3 of the way from the large battery cable attachment to the generator harness.) Use a stubby #2 Phillips screwdriver to break it loose and then loosen the screw with a small pocket screwdriver. The screw may hang up on the plastic cover on the rear of the generator. If this happens, use a pocket screwdriver inserted between the screw and the cover. The screw will pop out when a little sideways pressure is applied. Install the screw and washer from the kit through the voltage regulator and into the generator case. Tighten the screw securely. Replace the wiper module cover. Reconnect the battery cable. Tighten Tighten the cable to 15 N?m (11 lb ft).Parts InformationPart NumberDescription10316685Kit, Screw for Bosch Generator