For those electronics guru's..

[di0de]

So, I'm riding home from work as usual and all of a sudden my console lights turn rather bright then my battery lamp and ABS lamp illuminates. My headlights are also brighter than usual, and next thing I know my entire gauge cluster is wacked up (all needles randomly going up/down). So when I make it home, I disconnect the alternator and negative battery lead for ~10 min. Now everything looks okay after a brief drive, but my battery lamp is still lit and my console light appears to be *slightly* dim. Battery still checks out right around 12VDC.. just curious if I need to change it or what's happening? (I have a 99 GT w/ the same Motorcraft battery)

 

[n0v8or]

Three possibilities:
(1) Poor battery connection . . clean and tighten at both battery posts.
(2) A failing battery with an intermittent high impedance cell. After 4-5 years of use, the original battery is about due for replacement anyway. Once one gets to this stage, complete failure is not far away.
(3) A voltage regulator (built into the alternator) that stops working when hot.

My bet is on (2). Replacing the battery is a good idea even if you might be able to nurse it along for another year or two. Better than finding you cannot start the car some cold winter morning. A battery replacement will take care of (1) as well.

 

[di0de]

Thanks for the response.. I was hoping that a faulty battery could cause the regulator to act up as it did last night. The drive this morning went just fine, except for slow wiper movement and the battery light was still on. I think I'll drop a new one in today...

 

[NFCStang]

I'm going to guess battery as well. My lod 5.0 did the same thing. New Battery took care of it

 

[claytucc3]

My guess would be a bad battery or a bad ground to the GEM module. I have had that happen to me do to both of these things on 2 different occasions.

Mike

 

[di0de]

Well.. new battery is in, however the battery lamp is still on. I'm guessing the next step would be a new alternator/voltage regulator..

 

['96&'01Stang]

Is there a way to get your alternator checked before replacing it/

 

[di0de]

Yes, Autozone (and possibly Advance Auto) will check them/your battery for free.

 

[di0de]

Just to put some closure to this for the archives, I replaced the battery but it didn't fix the charging problem (battery light stayed on). After a new alternator, everything works great. Appears it must've been the voltage regulator...

 

[COramprat]

Just to put some closure to this for the archives, I replaced the battery but it didn't fix the charging problem (battery light stayed on). After a new alternator, everything works great. Appears it must've been the voltage regulator...

In case someone else comes along, I had a bad alt and had it rebuilt. Cost $90 less than a new/rebuild from Autozone and the shop gave me a lifetime warrenty. Just in case you want to save some cash.

 

[Sam98]

The voltage regulator is the only part of the electrical system that is likely cause the symptoms you described. The lights can only get brighter when the voltage is too high. You can verify that by measuring the battery voltage with the engine running. Neither the battery nor the generator can cause the voltage to be too high. The fact that the generator can get the voltage that high is evidence that it is working. Replace the voltage regulator before you drive around any more or you may fry the PCM or have the battery explode and have much more expensive repairs to deal with.