Headlights dim while driving

[CptFantaztic]

Was driving down Interstate last night when I noticed that the headlights dimmed for just a sec. Thought at first I was just blinking an my eyes were playing tricks on me. Wife noticed it too. She said that it has done it before to her (its her car). Motor never acted up and it did it twice in a 70 mile trip. They just dimmed and came right back to normal. Battery is new. Any suggestions?

[ricebike]

condition of the drive belt? check the belt deflection?

if it's just one serpentine belt, check the tensioner...

this is only a guess

[shorod]

You don't happen to have one of those little charging system testers with three LEDs that you plug in to an accessory port, do you? If so, you could plug it in and have your wife check it next time the lights flicker to see if the entire charging system is dropping in voltage.

Did it correspond to the A/C compressor kicking in or something possibly? You may want to check the battery cables at the battery to make sure they are clean and tight. Also, depending on the model year, there may be a TSB for either a headlight switch connection or connection near the headlights. I don't recall if that was the Taurus or one of the other models I monitor. A search of this forum though could probably identify if that's the Taurus and if so, what years are impacted.

-Rod

[ricebike]

looks like it's closely related to his OTHER thread:

http://www.automotiveforums.com/vbul....php?t=1061996

so now my guess about the belt / tensioner is somewhat valid, but may not be a fix...

[shorod]

Although if the belt were not staying properly tensioned, the load from the A/C compressor would likely cause a squeal or belt slip rather than dragging the engine down. It's still worth checking though.

-Rod

[Scrapper]

Originally Posted by CptFantaztic

Was driving down Interstate last night when I noticed that the headlights dimmed for just a sec. Thought at first I was just blinking an my eyes were playing tricks on me. Wife noticed it too. She said that it has done it before to her (its her car). Motor never acted up and it did it twice in a 70 mile trip. They just dimmed and came right back to normal. Battery is new. Any suggestions?

could it be ground wire from the moter to the car? and i'm not talking about the ground wire from the battery to the moter. i'd atleast check to see because that will do it.

good luck...

[CptFantaztic]

Originally Posted by shorod

Although if the belt were not staying properly tensioned, the load from the A/C compressor would likely cause a squeal or belt slip rather than dragging the engine down. It's still worth checking though.

-Rod

Thanks. I have replaced the tensioners, belt, had alternater rebuilt, new battery, power steering pump flushed, and AC compressor checked. All seems good. Have driven it almost a year since last problem(idle dropping at red light) with no problems. Just started this one it seems.

[SteveG3]

Originally Posted by CptFantaztic

Was driving down Interstate last night when I noticed that the headlights dimmed for just a sec. Thought at first I was just blinking an my eyes were playing tricks on me. Wife noticed it too. She said that it has done it before to her (its her car). Motor never acted up and it did it twice in a 70 mile trip. They just dimmed and came right back to normal. Battery is new. Any suggestions?

A telltale sign. I have had this on both my Taurus. Each time it was the alternator.
Some places will test your charging system for free. I am sure that will be it.
It will gradually get worse and will leave you stranded. Trust me I know.

[danielsatur]

A old/bad battery puts too much of a demand on the alternator,
I would rather replace a battery every 4-years than having to replace both.

[SteveG3]

Originally Posted by danielsatur

A old/bad battery puts too much of a demand on the alternator,
I would rather replace a battery every 4-years than having to replace both.

FYI. Both times I had a new battery.

[danielsatur]

You can also buy more charging time, if all the bells + whistles are turned off a few miles prior to destination, and don't turn them on until a cold start engine is operating at normal temp.

This will give you a fully charged battery a less of a load & demand during a cold start.
You also may consider to disabled Daytime running lights + use LED for turn/tail/stop/dome to save power.

[danielsatur]

Originally Posted by SteveG3

FYI. Both times I had a new battery.

Bad connections, or bad battery cables will cause a no charge, thus putting more of a demand on your alternator.

Caution - For a Dead battery
Always use an outside source to charge your battery fully, Not a Jump start and let the alternator do it.

See average life of battery, see http://www.automotiveforums.com/vbul...d.php?t=120360

[Willyum]

Mine on my '02 were doing that and eventually would go off for short periods.
It was the dashboard switch.