Dimming, what can be the cause of this??

[Mark6]

On my 82 mark vi as you can see in the video below, my interior lights dim but when I give it some gas it gets brighter, is this normal or sign of a failing alternator or not the right size battery? https://streamable.com/x80nj0?src=player-page-share

[Mike]

A weak battery or bad wiring can do that. If everything else is good a bad voltage regulator will also cause that. Typically the headlights will brighten and dim too.

[Dan Szwarc]

Mike is right. I'd start with the regulator, but a weak alternator it could also be. You can have the alternator tested at your local shop if they are not complete idiots. Warning: cheap chinese regulators are also BAD off the shelf so keep your old one, just in case. THe same may be true of alternators.

[papawayne]

I have a Ford Taurus station wagon of indeterminate year. and the brakes will dim the headlights first thing in the morning at dark thirty. I have learned to live with it, because it only happens in the morning once. Something tells me this is normal, but I will ask. Wayne

[frasern]

Wayne; Check the grounds on the taillights, explaining why would be wordy, but that's always the first thing to check. Same goes for Mark6, cleaning up all the grounds you can find will never hurt anything, it's free, and may prevent a future problem you haven't even thought of yet.

[papawayne]

Tis true. I soldered an extra ground wire to the taillights on my 63 and they beamed wonderfully. after not working at all. I don't know whose idea it was in design to have them pick up their ground just from the sockets pushed into a hole in the body. Wayne

[Lee]

If it does that all the time, I’d say you have a problem. But if you only notice it in the first few minutes after starting, and there is no alternator light glowing, I wouldn’t worry about it. You don’t get full alternator output at idle speed, and it’s busy recharging the battery right after you start it. I will see that effect on all my cars from time to time, and to some degree; generators are typically worse than alternators. You see it much less if you keep the battery fully charged on a trickle charger all the time like I do.

If you think there’s still a problem, you can get a cheap digital voltmeter you plug into the cigarette lighter, if you want to monitor the system voltage while you drive.

[Mark6]

Where's the voltage regulator located in a 82? I'll try to get the alternator/battery tested with a volt meter I got

[TonyC]

That was a question I was about to ask myself. I know that, after a certain year, Ford followed GM's lead (again) and designed an alternator with an integrated regulator. If one or the other fails, the whole unit comes out for replacement. But I don't know exactly what year that started.

On a side note (but related), I have noticed a similar issue with Frankenstein during initial start-ups at night, from the dash lights; it's like they're pulsating. But I have not yet suffered any battery drain, nor the idiot light flickering on and off; so I've let it be so far.

My alternator has only the then-stock capacity of 55 amps, the only one O'Reilly has to fit Frankenstein. It's held up for 2-1/2 years, and I do have a new spare with a 70-amp capacity (bought that about a year ago off E-Bay) should the one installed pack it up. Trick is, however, that I'd need somebody to swap the pulleys between old and new; so I'd be pretty much hosed if the alternator failed me on an isolated roadway, even if I had the new one on-hand with me.

---Tony

[Mike]

When I looked it up on rock auto it still listed a seperate voltage regulator. Especially with questionable parts these days it's a lot easier when they're seperate.