I know I’m probably answering my own question here, but I’ve been getting the voltage warning light and dash lights dim/brighten no matter if I’m driving or idling. It comes on and STAYS on until the car is shut off.
I previously noticed the tensioner is likely bad, as the car starts with a squeaky belt and the belt never truly stops squeaking. Its faint but its there. Damp days, forget about it because it will squeak forever. Belt is in good shape so…Bam, obviously the tensioner.
Previous owner put a new alternator and battery in it right before I got it.
If you didn’t replace the belt, you don’t know how old it is. If you’re replacing the tensioner, replace the belt. But are you saying the belt is slipping? That’s the only reason it would cause low voltage. If it’s slipping replace the belt for sure!
Do you know it’s the tensioner, and not one of the idler pulleys, or the bearing on the alternator, or power steering pump? For that matter, you’re assuming (I think) that the tensioner bearing is going, but it could be tensioner spring not holding belt tight enough.
Can you borrow a mechanic’s stethoscope?; it will let you isolate any bearing noise. Better to diagnose before throwing parts at a problem. In any event, since you’re going to have to remove the belt, check it off the car, bend backwards a little and look for cracking, or, just change it, they’re around $18
But… voltage drop? The alternator could be defective, is the regulator on that car on the alternator, or, part of the computer system. You might do better at a FORD or FOCUS specific owners club on the net. Good Luck !.
Well, I fixed the problem. The alternator was installed with a cross threaded nut on the terminal and not tightened, so the spade was jiggling around and zapping away the metal around it. Explains why the issue was becoming worse, as the room to jiggle was increasing with each contact. Broke the terminal while trying to remove the cross threaded nut and made it a fun fix…
Well, I was going to weld the spade to the terminal, the. I discovered that when I flaked the insulator away, there was a deep nut at the base. I was able to remove the half melted nut and put the spade beneath it rather than on top. Voltages read correctly now and the power fluctuation is gone.
