I have a 1994 Isuzu Rodeo, w/ 103k miles, which a few days ago started making the tell tale “need to replace the fan belt” sound. Shortly thereafter, several things also started happening: 1) the dashboard voltage indicator regularly shows between 8 and 12 (my choices are 8, 12 & 16), and this gets lower as I use either the headlights or heater; 2) as the battery ‘drains’ while the car is driven, getting near, or once below, 8 the car begins to hesitate and the “Check Trans” warning light begins to flash. Once I turn off the heater and/or headlights, the voltage meter ‘rebounds’ to 12 or just below, and the “Check Trans” light goes off, and the car runs reasonably normally. The battery is three weeks old, I actually replaced it in preparation for winter (I am in Chicago).
My question is, could this be an alternator problem, and if so, is it related to the fan belt wear, or is it something else? The rest of the car is in pristine condition.
If the fan belt is bad, that would account for your problem. Increased electrical load can cause the belt to slip. (Assuming it is there at all)