Voltage Gauge

[Lazzman]

At times, after my '98 Sport has been sitting a while I will start it up and the voltage gauge will drop to the last white line, just above the red line and stay there for about 20 mintues of driving, then it will go back to the normal halfway position.

The Battery is a Motorcraft and was Purchased in 2004. I did a cold voltage test on the battery and it read 12.74 volts. I have not gotten a shudder or slow crank since this problem has been going on.

Next I thought it might be the alternator, but I replaced the alternator with a brand new (not remanufactured) 130amp unit from NAPA less than two years ago. The lights never dim even when the volt gauge is in the very low position. I checked the serpentine belt which is spinning on everything fine, it is a Goodyear Gatorback and less than two years old.

Anybody have any specualtion as to what this could be? It has happened about 5 time over the last two months, since I first noticed it. Only happens if the vehicle was sitting for at least 5 hours or so- gauge always stays low for about 20 minutes of driving then pops back to halfway.

If it is the alternator I do not want to find out the hard way like I did 2yrs back on the highway. All of my systems including steering and ABS failed.

Thanks

 

[BrooklynBay]

The auto parts store could test your alternator, and battery. Check the battery terminals first.

 

[Lazzman]

Thanks Brooklyn.

The terminals are clean, I use anti corrode on them and everything appears tight.

I will check with the autoparts store.

 

[aldive]

Did you check the alternator output voltage?

 

[Lazzman]

Not yet, But I guess I should.

One would think that a brand new alternator would last a bit longer than 10,000mi.

 

[aldive]

Not yet, But I guess I should.

One would think that a brand new alternator would last a bit longer than 10,000mi.

Don't condemn the alternator until you diagnose the problem.

 

[Jakee]

Lazz - Do you have the underdrive crank pulley?

 

[aldive]

bump

 

[Jakee]

I had this problem. Added the undrive alt pulley and the problem went away.

 

[aldive]

I had this problem. Added the undrive alt pulley and the problem went away.

Please explain.

 

[Jakee]

Sorry for the no explanation.

What I saw was the volt gage reading really low on start-up and low until I reved the engine up to driving speeds. (driving speeds for a few minutes) Sometimes the dummy light would come on, and I'd rev the engine and it would go off. So, I added the OVERDRIVE alt pulley (I think I called it underdrive by mistake) and the problem went away. It's been around a month so I'm sure this is what it was.

It doesn't sound exactly like Laz's problem but maybe it would be worth looking into if he did have the underdrive crank pulley.

 

[sumless]

Gauge?

Hiya,

Since your not seeing any diming in the drive lights, and seemed to have gone after all the culprits, is it possible your Gauge might be mis-reading?
I know I have seem a fare share of bad grounding issues with these display
panels and of course heating up resolves them, perhaps this is the case?

Dunno, good luck.
-Joe