Alternator? Batt? Volt Regulator? Which one?

[jwdeeming]

The worlds most dangerous shadetree mechanic is at it again...



Wife's 2003 died this week. Monday it had to be jumpstarted after record setting -20F temps and a gelled fuel episode. All seemed fine until Thur when it died on the road. Dead batteries.



Jumpstarted again but Check Gauges lights came on after a short distance. I told her to head to local parts store and have the batts/alternator tested. Diagnosis was batteries are fine but alternator is bad. Got a new one and installed it yesterday.



Batteries have and seem to hold a full charge. Gauge starts out looking normal - approx 13v - however after driving about 1/4 mile down our bumpy gravel driveway with lights on, the Check Gauges light comes back on and volt meter snaps down to zero. I brought it home, shut down, tested batts with a voltmeter and they are still at 13. 5 volts. Started truck again and repeated. Same failure at almost the same spot in the driveway.



Based on some reading here, I have verified the batt voltage at 13. 5 with the truck off. Also measured voltage at the bolt on the back of the alternator and it is also 13. 5. Battery terminals are clean, I cleaned and dilectric-greased the plug connector on the alternator. Serp belt is tight and in good shape.



Questions are:

1. Could I have killed a brand new alternator?

2. Is it possible the parts store misdiagnosed and these batteries are not healthy after all? They are the original batts on a 2003...

3. Is it possibly the voltage regulator? If so, is there a way to diagnose before buying new?



I can not sort out from my reading here whether the voltage regulator is a seperate component from the PCM, but that doesn't matter since I don't have a clue where either one is.



Any suggestions would be greatly appreciated.

Thanks!



Jim



on edit: Forgot to add that there are no codes set, according to the reader I have.

 

[Road Dog]

You can't test a battery with a volt meter. You need a load tester. Most battery shops will test for free. you can also check the water level in each cell (there's no such thing as a "maintenance-free" battery).

The voltage regulator is inside the PCM so if it's failed then you need a new PCM. It's on the passenger side of the firewall.

 

[LRutigliano]

-20F ambient and the original 2003 batteries...



Your batteries are the most likely culprit here.



Your post is kinda confusing... I'm not sure what you have replaced and what is original. With newer vehicles and all of the electronics on them, the batteries no longer give you a warning that something is wrong with them, they just die, all at once with no warning prior to that...



13. 5v measured at the batteries with the engine off isn't really telling you the whole story. Your batteries can only measure 12. 6v when they are 100% charged. You are reading 13. 5v most likely as soon as the engine is turned off and you are measuring residual from the alternator charging voltage that was pumped into the batteries.



Your batteries need be to load tested to check if they are good or bad. You can get the parts store to do it or you can go buy a load tester at Harbor Freight for cheap...



In order for your alternator and PCM to work correctly, you need good batteries. Many of your over the road gremlins are most likely due to the old batteries.

 

[jwdeeming]

Put new batteries in - that seems to have been the culprit.

 

[jelag]

As batteries age... . they shed material off the sides of the cells... this piles up at the bottom of the battery case and yields that portion of the cell that covered with the scale useless... . if you were to see a battery inside the plates are off the bottom of the battery to give room for the scale... . so what's happening is that your limiting the capacity of the battery.....

The other type of battery failure from old age is a chemical process where the battery will not accept a charge from the charging system... its internal resistance is too high... . in some cases a battery charger will charge this battery, as the charger will have the ability to overcome the internal resistance and the charger will go to something like 16 volts and charge...

We used to run what was called a 3 minute charge test... we'd set the charger for 40 amps output and wouldn't touch the charger... at the end of 3 minutes you check the battery voltage... if at that time the voltage is over 15. 5 volts that battery will come up to a full charge with the charger but will never come up to a full charge on the vehicle. .

When one battery dies from either one of the two conditions mentioned above you've got to change both of them...

Hope this gives you an insight to whats going on. .

 

[DennyDay]

ALSO - - Check the load the air intake heaters are taking. Some times, w/low voltage the relays will hang up in the closed position (on) and cause all kinds of problems, including battery failure, alternator failure and heat grid burnout. Had this happen to an '02 we owned. Ended up replacing both relays, grid heater, both batteries and the alternator - - It was about 12F that day.



Denny

 

[AJain]

I had the same experience as Jim earlier this week. After a normal startup and a few minutes of driving, the voltmeter dropped to about 8 volts and the check guages light came on. It happened for a few hours during one particularly cold day, but hasn't repeated the problem since.

However, I checked the trouble codes at the time, and saw a code P2502. Here's what the 2004 Dodge service manual sez about a code P2502:

"When monitored: While the engine is running.

Set Condition: The ECM cycles the voltage regulator in the generator while monitoring for a change in output voltage. If the voltage does not drop when the regulator is off, the fault is set.

Possible causes:
Dirty of loose connections
High resistance in the B+ circuit
High resistance in the B+ cross over cable
High resistance in the ground circuit
Generator
ECM
Intermittent condition"

It also lists a troubleshooting procedure for checking voltages between different generator and battery posts, which I did to rule out the high resistance possibility.

It says to check and clean generator and ECM connectors, as necessary. Didn't get the chance to do this myself, as I'm afraid of breaking a connector in these zero-ish temps, and I don't have a garage :-(

Interestingly, I found that there is a TSB out (18-001-07) which addresses this same condition. The listed model of the TSB is the 2007 Dodge 2500/3500, but in the Note it says that "This bulletin applies to vehicles equipped with a 5. 9L engine built on or before Nov 29, 2006, so I'm wondering if this might also apply to my 2004. 5. The entire "repair procedure" that follows is simply a PCM reprogram/flash.

All that being said, at the moment my first inclination is to replace the batteries, even though they appear to still be ok, since they are now about 5 yrs old. How long have batteries been lasting for most folks before they have to be replaced?

aJ

 

[Andersonville]

My passenger side battery started cooking itself off last Feb. I replaced both of them at Wally World. What makes them do that? I had never had a battery do that. Nasty stink.