Low charging voltage after warm-restart: It isn't alternator or battery...

[phil-l]

Hi all -

This has baffled me - but I hope someone can shed some light.

I replaced the alternator in my '00 Windstar LX 3.8 late last year to solve a low-voltage charging problem - but the problem still appears intermittently. Here's the pattern I've noticed:

- If I start the van in the morning after sitting all night, charging voltage is about 14.1 V (measured with a quality digital multimeter), and stays consistent as I drive. This is correct behavior.

- If I turn off the van when warm - and restart a short time later, charging voltage is now stuck at about 13.3 to 13.5 volts, and will not climb back to full voltage. If my wife runs a series of errands during the day, the battery will become discharged to the point that my benchtop battery charger initially pushes 6-8 amps to bring it back up to full voltage that evening. If I don't charge it manually every day or so, she'll end up needing a jump in just a few days.

At first, I was sure I was the victim of a set of bad alternator regulators. After 3 alternators (that's another story), I'm convinced the alternator itself is fine (and I can now swap Windstar alternators in under 15 minutes).

I also tried swapping out the battery with another vehicle - just to make sure a bad cell or something similar wasn't causing problems. I see the same symptoms.

I've cleaned, tightened and checked ground terminals, battery terminals and alternator connections. I've measured the voltage drop and resistance across major cables between the alternator, battery and chassis ground. In general, voltage drops are under 0.15 V - which is fine based on what I've read. Comparable resistances are no more than 1 to 2 ohms (it's difficult to get good low-resistance readings on these cables). I was also suspicious of the fusible links in the wiring harness - but they check out OK.

I now suspect either a problem that affects the +12V ignition supply to the alternator (not the field supply line - which is direct to the battery through a fusible link and checks out OK). Could it be a marginal relay that works when cold - but doesn't completely close when warm? Could it be a wiring harness problem that's affected by vehicle movement and difficult to track down? I'm not sure.

I appreciate any guidance from the Windstar community!

[12Ounce]

Keep swapping those alternators! And checking those cables and connections ... .15v is far too much cable voltage drop I think!

When swapping alternators with aftermarket suppliers, I ask for a bench test on the "new" replacement. More than once, they have found problems with the unit they were about to send me out the door with.

The alternator is really "stand alone" in the circuit ... it needs no outside signal or control voltage. It should produce 14 volts anytime it is up to speed. Something is going haywire internally because of high temps, I would guess. There is a voltage feed back to the PCM, but this is for the benefit of the PCM, not for control of the alternator.

[danielsatur]

Take your Van to the local Auto Parts store, they can do a load test on both the battery & Alternator for free.

Do a visual inspection on battery, look for cable corrosion, and lose connectors,
This could cause resistance, thus both the battery + Alternator can't do it's job.

[wiswind]

I would agree with the in-vehicle test of the battery and alternator.
In my '96, there was a fuse "T" for the alternator that........if blown, you will not get any charging.
I do not know if that was removed in the newer windstars......or what year it would have been removed.
Someone had posted a while back that they did not use this fuse in newer windstars.

Check the alternator ground to the chassis ground also.
Look for any signs of a burned connector........a loose crimp connector can look great on the terminal end, but be burned out inside the crimp to the wire.
Do this on all the connections.....including the battery, and ground connections......as well as the big power/ground connections on the back side of the power distribution box in the engine compartment (with all the relays inside).

[CnlK]

Several years ago, I installed 4 aftermarket alternators before I got good one. The first two would charge initially and then woudn't charge, the third would drain the battery with a 4.5 amp draw when van was off.
Check yours for a draw, I pulled main positve wire off alternator and checked with multimeter in series. Know what you mean about being able to pull and install one if 15 minutes.

Is the alternator pulley the same size as the original?

[phil-l]

A quick follow-up on this topic: I took the Windstar into the dealer for the rear axle and front subframe inspections - and asked them to check the charging system while they were in there.

The dealer claims it's a bad alternator. Mind you, the alternator they checked is the *third* freshly-rebuilt alternator I've put in the van in the last few months. The current alternator is an honest-to-goodness-from-the-dealer Ford rebuild. The previous two were from Duralast. The van exhibits the same intermittent low voltage situation with all of them - which is what led me to suspicion of other areas.

Of course, this points to an industry-wide problem with some aspect of the Windstar alternator rebuild process. Perhaps a batch of bad internal regulators?

Sadly, I won't be able to update the story for awhile: The dealer says my front subframe has corrosion in the right-rear mount point and is unsafe to drive. They don't expect repair parts to be available for 1 to 2 months, so I won't be able to definitively deal with the alternator situation until then.

[phil-l]

Another update: Yet more testing (with more accurate equipment) confirms no problems in the starter, alternator or battery. Yet the problem persists.

One potential culprit is the PCM. While I still have to complete more testing to confirm a PCM problem, I've started researching PCM replacement concerns in a new thread:


http://www.automotiveforums.com/vbul....php?p=6903658

[12Ounce]

Know anyone with exactly the same model year Winny as yours? Or at least close enough so the PCM's, alternators, harnesses will be the same? You need to make fast friends of such a person.

I have two daughters that have the same model car(s). I am the family mechanic. It is so convenient, when trouble shooting on these cars, to be able to swap components from one car to the other.

[phil-l]

Sadly, I know of no nearby 'compatible' Windstar owners. Yes, this would have greatly helped my problem research efforts. In particular, I could have positively verified alternator concerns in a short amount of time...

[mark_gober]

Originally Posted by 12Ounce

Know anyone with exactly the same model year Winny as yours? Or at least close enough so the PCM's, alternators, harnesses will be the same? You need to make fast friends of such a person.

I have two daughters that have the same model car(s). I am the family mechanic. It is so convenient, when trouble shooting on these cars, to be able to swap components from one car to the other.

I agree! I have a 2000 Windstar and 1995. My brother has a 2003 and it is great to swap parts for free before I buy anything.