Power struggle. What tension!

2002 Ford Focus SE ZX5 SPI

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.

Is my tensioner allowing this voltage drop?

How do you know the belt is in good shape?


Looked at it. Looks recently replaced. No cracks or weathering, not worn.

Rookie mistake.


Basically I’m looking into the voltage drop. Be it the tensioner or the belt, both are simple fixes, I’m just sighting my crosshairs.

That is a nice ad for gates belt gauges though. Got the video and everything. I’d give that out on a business card if I worked for Gates.

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!

Isn’t this the vehicle that has wacky door lock problems . If so you might need a auto electric shop to see what really is going on .

This IS the wacky locks car. Its actually got a list of problems, however I don’t believe the locks are associated with the voltage drop.

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 !.

Did you fix the locks?
Did you look at my reply to that discussion?

:palm_tree: :sunglasses: :palm_tree:

Yes, sorry for the late reply. Voltage issue unaffected however.

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…

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It’ll be easiest to just install a remanufactured alternator at this point

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.