My 2003 Ford Taurus with 172K miles has a recurring loss of power while driving. It happened several times almost 3 years ago and after 3 alternators and finally a new battery, the problem seemed to be resolved. Now it has started happening again, and more frequently. Instead of happening approx every 4-6 weeks, it is now happening on a daily basis.
While driving, could be 25 mph or 65 mph, could be a mile from home or 100 miles from home, the car suddenly starts losing power. The malfunction indicator lights start coming on, first the ABS and airbag lights, then the battery light, then pretty much everything. The tachometer is the first gauge to go, and then the speedometer, temp, etc. all go at the same time several seconds later. At the same time, the dash lights, radio, headlights, horn, etc. are all quickly fading.
Through a series of unfortunate events, we have discovered that if you keep driving and do not stop the car, everything will spring back to life shortly. However, if you (like me), pull over and stop the car or let it coast, it will stall out and it will not start up right away. It will click, but not turn over. But, let it sit for a few hours, and it starts back up with no troubles.
Since June we have replaced the battery, the alternator at least 3 times, the spark plugs & wires, the 175 amp AMG fuse, and the negative grounds from the battery.
One trip to the local AutoZone resulted in 7 tests of the alternator that were good. That alternator was a month old, and has since been replaced after testing bad.
It’s scheduled to go into a shop claiming to have electrical expertise, but I would appreciate any ideas. This will be the 4th different shop, and my husband, FIL, and dad are all clueless (and they’re good DIY mechanics).
I can verify that each alternator since June has been bench tested, not just swapped out on a hunch, and that the battery cables have been checked, cleaned, and greased meticulously.
We would rather not have a car payment at this point in our lives, but we may as well with what we’ve been paying in repairs and inconvenience. Hoping you car buffs can point us in the right direction!
I would guess at this point batteries and alternators are not the problem. So that leaves other options in order of my preference.
Bad connection, at battery or ground.
Bad ignition switch
Bad Belt
Bad Voltage regulator.
One needs to have a good mechanic to diagnose the problem, and repair only what needs to be repaired.
I don’t know much about cars, but after a few times, even I know to stop looking at the alternator all by itself. 
I can’t remember if my dad mentioned it or if I read it somewhere, but would the alternator have an internal voltage regulator? We haven’t noticed any noise from the belt. Last time I had it replaced, it had been emitting a nasty squeal for about a day or so after it would rain and we haven’t heard a peep. With all of the maintenance activity, is it possible something got knocked out of whack so that’s it’s maladjusted somehow? And when you say a bad ground, how many are there to check, other than the ones that were just replaced? Thanks.
There are several weak points in the wiring of that car that can cause grief but a weak ground sounds like your problem. There are several grounds under the hood and each one should be taken apart and cleaned well. The grounds are somewhat redundant and if one has built up a significant resistance and results in too much current being carried to a lighter connection it will cause problems whenever the capacity of that ground is exceeded. The battery cable ground should be the starting point. That sheet metal ring from the factory has sent many good batteries and alternators to the scrap heap.
Yes, modern alternator s have the voltage regulators built into them.
I’m wondering of you’re experiencing fuel pressure loss.
Autozone, Advanced, PepBoys and the like use crappy rebuilt alternators & starters. NAPA is the only aftermarket place that I would by them from.
I would suggest checking all cables attached to the battery. That means removing BOTH ends and cleaning both the cable clamp and the fitting on the battery. Also while you have that cable out, check the resistance of each cable while you pull push turn twist the cable. They can go bad internally. just for fun, I would include the same for any cable on the alternator.Yes, modern alternator s have the voltage regulators built into them.
You are probably correct. However, the 1989 Mercury Sable (similar to the Ford Taurus) that I owned had a voltage regulator that was separate from the alternator. Ford may have gone to a voltage regulator internal to the alternator by 2003, but it wouldn’t hurt to check to see if this is a possibility.
Thanks for the ideas. Here’s the lastest… The shop called Saturday and they couldn’t find anything yet. We agreed to let them keep the car over the weekend and take a look at it again this morning. We’re hoping that since it has been sitting, the issue will present itself again. Unfortunately, I am headed out of town and my husband is in school and working, so he has limited time to try to figure it out on his own.
We did some research over the weekend and discovered that the Taurus is worth a lot less than we previously thought, so we may end up trying to get rid of it if it doesn’t get resolved soon, since we wouldn’t be taking quite a big of hit as we thought.
Shop #2 couldn’t find any problem. They graciously did not charge us for their diagnostic work since they were unable to determine the cause of our problem. If we ever do find the problem, I’ll post it for our mutual enjoyment.
If you’ve replaced batteries and numerious alternators and still have the problem, the problem is in the voltage regulator. However, there is no seperate voltage regulator mounted under the hood. Nor is there a voltage regulator located inside the alternator. The voltage is regulated by the ECU or engine computer.
Go to a local auto recyler with the ECU, and they may be able to match it up with a used one.
Tester
I drive a 2000 Windstar minivan, and the same thing happened to me last night.It happens to other models of Ford as well. I found this:
http://www.arfc.org/complaints/2000/ford/windstar/electrical_system/problem.aspx
I will add that your policy of stopping and checking things out is the correct one, perhaps this could be done without shutting down the engine (I see you say an engine stall out is involved).
One thing I don’t like is that a battery can provide a substancial period where the car can be operated with a non-functing alternaor but in your case it appears that driveability issues (driveabily is a term used when you want to move the conversation into areas concerning how the car runs) very quickly (like minutes) follow the illumination of your battery light. I would not discount this observation until it can be explained.