'94 s-10, 2.2 L, 4 cyl. Fuel injected.
Engine gets bad mileage. Headlights and instrument lights dim sporadically. Gauges, speedo, & tach occasionally slip to lower reading also sporadically but not always in sync w/ dim lights or each other. Both are worse when the headlights are on. I'm guessing it's a ground or volt regulator, (or something). Can someone suggest an isolation test procedure?

 

Yes, I'd say loose connection(s)

 

Any luck?test alternator at parts store?

 

it's not registered so I can't drive into town, it's also raining so I'm still considering what to do. kind of a relief to find the lights flicker, since I hadn't driven it at night. I suspect there probably are a couple of bad connections like kevinpk said. I'm suspicious of multiple problems doing the same thing though. maybe a bunch of terminal clips corroded while sitting outdoors for 5 yrs.

update 30 sept 4:00 found a piece of tinfoil stuffed in one of the fuse slots but according to the schematic on the cover that location (#5) isn't connected to anything. the volt meter shows better charging though (14 instead of 12). the fuse box might still have a ground fault, the tach needle wiggled only once when I drove it down the hill (that's an improvement).