2002 Ford Taurus 32v DOHC - Battery light is on

I have a 2002 Taurus that I had let my friends use for the past year. Now that I have it back I notice 2 things. Not sure if they are related.

  1. Check engine light is on. (it’s just a picture of an engine which I assume means check engine).

  2. The battery light is on.

A parts store hooked up a battery tester and it seemed okay. He said he would also test the alternator but he didn’t really hook any cables up to the alternator. He left it connected to the battery. I’m guessing he just changed the setting on the meter (analog).

Both were done with the car running, nothing running. And then with the a/c on. The load dropped some but still seemed normal.

Is it possible that the battery my friend put in it is possibly too small? The battery is new (May 2012). The car seems to be running fine except I noticed some “sputtering” (for lack of a better term) when I was driving it today with the cruise control on. It isn’t constant, just something that happened a couple of times. Also I noticed the engine try to jump out of the car when it was parked and testing the battery and I gunned it. I’m guessing a broken motor mount.

I’m going to take it to a shop on my next payday but just was wondering if anyone here might have a clue because I obviously don’t.

The battery light indicates a problem with the charging system, typically when alternator voltage falls below a certain threshhold.

It’s not because the battery’s too small.

It’s possible the battery light is due to a faulty alternator diode. I assume it’s charging enough that a jumper start hasn’t been needed.

It’s possible the check engine light is due to low charging voltage. Of course, there are several hundred other possibilities as well.

Most testing of alternators is done by measuring charging voltage, which can be measured at the battery. When the load is increased (e.g. lights or A/C turned on) the voltage may drop. Without knowing the specific voltage readings we can’t say what’s going on.

There should be a small single wire connector on the alternator, take it off and put it back on a few times to clean the connection, I’d bet ten bucks the light will go out.

Not according to my repair info.

You may be right, I know this is the case on many Ford alts., maybe not this one.

New information. I had the battery and alternator tested again at another parts store and it was normal. However, I also realized the manufacturer installed security system was removed and was in the compartment where the spare goes in the trunk after I lifted the carpet in the trunk. It doesn’t look like it was removed with a lot of care.

Could something from the removal of that be causing my battery light to be on? I have a Haynes book but I’m not really sure what to look for.

I just did some Google-fu and apparently the voltage regulator is a separate component on this car. I’m going to see about getting that checked.

You might need to have it tested by a shop with more expertise and equipment than the parts store.

I doubt it, but I can’t say it’s impossible.

I think whatever you found is incorrect. My repair info says the regulator is integral to the alternator. As far as I know, it’s been decades since any car sold in the U.S. had a separate voltage regulator. I can’t remember the last time I saw one.

Ok, but I did find this part here: http://www.partstrain.com/ShopByDepartment/Voltage_Regulator/FORD/TAURUS/2002

What repair manual are you looking at? I’ve got a Haynes that I purchased but am at work right now and will be looking when I get home this morning.

That part is the voltage regulator which is inside the alternator housing.

As to the single wire I mentioned previously, I stand corrected, there is none.

Ok, thanks. So it’s still possible that even though the alternator may test good that the voltage regulator inside it may not be. One thing I saw was this on justanswer.com:

Steve :
what turns the light on is the voltage regulator. The voltage rgulator is bad and is turning the light on. The voltage regulator is attached to the back of the alternator, Unfortunately this does not get replaced with a rebuild. or a so called new alternator…

The last part makes no sense because it seems a rebuilt must by definition include a “new” VR.

I’m going to take it in this Friday and have it hooked to a scope. I see no alternative.

Chrysler products for many years from the late '80’s to possibly current models had/have the regulator in the ECM. Common failure, many were converted to external regulator rather than replacing the ECM.

This doesn’t help this guy though, sorry for straying off course.

NP. Thanks for all the help I have received.

Guess I may as well disconnect and clean all the wires first though. Maybe I’ll get lucky.

I use ALLDATA, which is one of the most common sources of professional repair info (I own an auto repair shop). It indicates that the voltage regulator is not sold separately by Ford, and is only available with the complete alternator assembly. I have not called a Ford dealer to verify this, but ALLDATA essentially repackages factory repair info, so I have no reason to doubt it. I also checked with one of my main local parts sources, part of a nationwide chain, and they don’t list a separate regulator.

There was a time when alternator components were readily available – regulators, stators, brushes, bearings, etc. – and alternators were commonly rebuilt in the field. The market has evolved to where rebuilding by repair shops is rare to nonexistent (except by some specialty electrical shops) and the standard repair is to replace the whole unit. Part of the rationale for this is that when one component has failed, others are likely to follow soon. You might replace the regulator only to have, say, the brushes go out within a few months. This type of scenario often results in unhappy customers, so shops avoid doing partial repairs. By replacing the whole unit, they minimize the chance of having to deal with “You just fixed my alternator, and now it’s not working!” That regulator may well be available as you’ve found, but not through typical sources that most repair facilities use.

Yes, but I think more thorough testing would indicate a faulty regulator.

Bolding mine. Yes, you’re right. There are new alternators available, and they are completely new. Of course some will call a rebuilt alternator “new,” just as people often call the used car they just bought “my new car.” This is likely what he means by “so called new alternator.” It may be that some rebuilds reuse regulators that test good on the bench, however I suspect (but don’t know for certain) that the higher quality rebuilds routinely put in a new regulator.