Alternator Diagnosing

[Ed_Strong]

I have a battery drain in our 2000 Windstar LX 3.8L that would kill the battery if left connected over night. The Battery and Alternator were replaced back in 05/2010 and have been working fine ever since.

It all started a few week ago, as we were leaving for the weekend we moved the Windstar from "Spot A" to "Spot B" in the parking area in front of the house, so it was a quick start, reverse 10feet, move forward 10feet and shut off.

Came back and went to move the van back to "Spot A" and battery was dead (only 2.5V), jump started the van and started right up, then let it run to charge battery. I did some errands thru the day and parked it overnight.

Next day battery dead, but jump started right up again! With meter on Alt is putting about 14.5V. So started looking for other problems and realized I had 2 bulbs out on the High Mount Stop Light. So after replacing those the battery is still loosing charge if left connected.

Now I have to keep unplugging the Neg battery terminal when the van sits for fear of running the battery down, battery stays at 12.75V unplugged. when I plug the neg terminal it starts strong and runs fine and charges good.

Now I went to diagnose the Alt to see if it has an internal failure using the Chilton Manual procedure in Section 5 Chapter 10 but, the pictures don't match my unit. so I don't know if the tests are accurate!

Key Off Engine Off I got...
"B+" terminal at 12.5V with Key Off as manual indicates.

Key On Engine Off I got...
"A" terminal at 12V as manual indicates.
"I" terminal at .5V to .3V when manual calls for 1V
"B+" terminal at 12.5V as manual indicates..

Key On Engine On I got...
"A" terminal at 14.5V as manual indicates.
"I" terminal at 2.5V when manual calls for 13V to 14V
"B+" terminal at 14.5 as manual indicates.

So according to this test the "I" terminal on the Alt may be faulty... but I can't confirm since the picture on the manual is different to my Alt and the Alt on my van does not label this terminals.

[jdl]

With the engine running, if you have 14.5 volts at the alternator bat terminal and the same across battery posts. I don't think your charging system is the problem.

Maybe a lite is left on, interior--under the hood--somewhere. Best time to check is in the dark. Also, check for excessive amp draw with everything off. The generic amp draw specs is around 30--50 ma. That's not even a tenth of an amp. If the amp draw is excessive, pull/;replace fuses one at a time. When you pull the fuse on the faulty circuit, the amp draw returns to normal. Then you have to check everything on that fuse circuit.

[northern piper]

common cause is also a weak boo switch (brake on off). It's attached to the brake pedal and the spring looses some of its "ummff" and causes the brake lights to stay on.

[Ed_Strong]

Yeah... I've been monitoring the brake lights to see if they stay on. So far not an issue there! Rear wiper seems to be operating normal too!

Now to check for amp draw how do I go about it? Do I go check at the battery posts? or is there some other way to check for that? thanks

[northern piper]

checking current draw in not done in parallel but series. So, you'll need to detach the negative terminal on the battery, attach the negative test lead from your meter, set the meter to dc amps, then connect the opposite lead of the volt meter to the wire you've disconnected from the battery. The voltmeter will now read current in amps that travels through the meter. If you don't have a digital meter, I'd try to get one. An analog meter likely won't reveal the current accurately due to its lack of sensitivity.

Once you've got the meter correctly hooked up, you can watch to see what the draw is with everything off and it should be minimal. If there is a large draw, pulling fuses one by one may be the only way to go.

[12Ounce]

Well... I think you may have a bad alternator. Worth removing and taking to AutoZone for a bench test.

[Ed_Strong]

It sure looks that way...! but my problem is that I'm not sure the procedure from the Chilton's Book is accurate since the picture references are from different Alts than the one I own!

They looks like they're from 95 to 98 model years, guess I'll have to wait till the weekend to take it to AutoZone.

[Ed_Strong]

Update:

Managed to get the Alternator and Battery out and ran to AutoZone to get them bench tested...

Battery - Passed!
Alternator - Faiiled!

According to the tests, it failed the Voltage Regulator Test and I think the other was a Diode Test (sorry cannot remember exactly)...!

----------------------------------------

Just for kicks I also went to Advanced Auto Parts a little farther down the road to re-test and...

Battery Passed!
Alternator Faiiled!

But this time it failed a Stator Test and some AC Output Test if I remember it right. I tried to see if there was a regulator test included on theirs and if it had passed, but could not find it!

Would it be wise to just replace the voltage regulator and see if that fixes it? I'm really short on cash and cannot afford $185 for a new Alt, for the time being I put the Alt back in the van and I'll just keep unplugging the battery when not driving as long as it keeps charging!

[DeltaP]

Two or more shorted diodes in an alternator will drain a battery overnight.

[scubacat]

When you replaced the alternator last time, did you get a lifetime warranty?

[12Ounce]

Originally Posted by scubacat

When you replaced the alternator last time, did you get a lifetime warranty?

My thoughts also .... AutoZone is really good about backing their products.

[Ed_Strong]

Nope, sadly I got the one year warranty deal... just like now it was all I could afford! This car seems to always break down when I least can afford to fix it

[jdl]

Glad you got it going your way.

[northern piper]

have you considered looking at a place like rockauto.com? I just did a quick search and they sell your alt for $112. Maybe that's a less expensive alternative?

[scubacat]

Given the occasional "miss" on rebuild quality of wear-parts like starters and alternators, I usually opt for autozone or advance auto with the lifetime warranty. It usually ends up a lot cheaper in the long run. Plus, when you bring it in for a test, you can just do a warranty swap right there and then if it's bad.

Check advance auto with an internet coupon. I can often get close or sometimes even beat rockauto or amazon with them.