Alternator Dying-Updated 1/1/11

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TrainTrac

TrainTrac

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Well, after 109,000 miles and 6.5 years; my alternator's dying. Had it tested at both Autozone & Advance Auto w/same conclusion: Bad diode in the alternator is draining the battery when the Trac's shut off. However, there are two different replacement part numbers (and $40 price difference) depending on build d date. And of course, mine calls for the more expensive one ($220 new). So what changed 1/2-way through the 2004 production year regarding alternators? Not happy about having to buy the more expensive one...
 
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I wouldn't trust there diagnosis in a million years, am curious how they came to the conclusion that it was the alternator that was pulling draining the battery with the ignition off especially since the Fords don't shut down until about 45 minutes after the key is turned off and taken out of the ignition.
 
They changed the wiring on the alternator and the amp output...



The older one is the 3 wire (Fire) plug.. LOL.... and then the new style is a single bolt on power wire...



Todd Z
 
If you want to test the diode theory, remove the hot wire from the alternator when you park it for the night. Put the wire back on in the morning.



If it starts up, then it probably is the diode, if not, you have something else discharging your battery...
 
I wouldn't trust there diagnosis in a million years, am curious how they came to the conclusion that it was the alternator that was pulling draining the battery with the ignition off especially since the Fords don't shut down until about 45 minutes after the key is turned off and taken out of the ignition.
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The guy at Advance Auto also stuck a multimeter across the battery with the Trac off. You could see the battery slowly draining. Both stores used their electrical system system diagnostic machines to prove the battery good and alternator bad. So something's draining the battery. Bad diodes in the alternator seem like a likely culprit after 109k miles to me. If that's not it, I'm open to suggestions that would drain the battery, but not cause other electrical problems.
 
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Not familiar with the modern ford altenator. I used to replace the diodes and regulators myself. profided the bearings were good. The windings and armature are coated bullit proof, IMO.



"DISCLAIMER, ALL THIS INFO IS POSIBILITIES"

 
TrainTrac,11/15/2010 18:42 MT





The guy at Advance Auto also stuck a multimeter across the battery with the Trac off. You could see the battery slowly draining. Both stores used their electrical system system diagnostic machines to prove the battery good and alternator bad. So something's draining the battery. Bad diodes in the alternator seem like a likely culprit after 109k miles to me. If that's not it, I'm open to suggestions that would drain the battery, but not cause other electrical problems.
Click to expand...



This is what I am trying to tell you. Once the vehicle is shut off the battery will continue to discharge for 45 minutes until all the vehicle systems shut down...the idiot at Advance Auto has no clue as to what he is doing. Is there a possibility that the alternator is casuing it...sure but I can't remember the last time I saw an alternator cause this issue on a late model vehicle.



These systems are a pain in the but to check becasue you have to disconnect the battery - cable and then put an ammeter inline and then wait 45 minutes for the system to time out until you can determine if you have a draw or not...that is if you don't have the scan tool to force the system to go into sleep mode. What sucks is if you accidentially wake the system up by opening a door or something stupid like that becasue once the system wakes up it takes another 45 minutes.



I sure would hate to see you spend the money replacing the alternator based on the uneducated decision of the sales clerk at Advance.
 
How old is the battery? And before I purchased an alternator, I would remove it and have it checked. If the problems is one of the diodes, it will show up on a bench test.
 
l1tech,

I have never heard that Ford's do not shut down everything when you switch the key off?? What is the purpose for that, and why does it take up to 45 minutes to complete the shut down?



I know that some things like radios, clocks and some other electronic devices like alarms and remote locks require a small amount of battery power while the ignition is off, but what else is using battery power for 45 minutes after the key is shut off??



I know that some cars with electric fans can have the fan run for a few minutes after being parked, but nothing close to 45 minutes.



...Rich
 
A battery is 12.6 (+ or -) when idle...... after the truck is running it will be sitting in the 14's.... IT takes time for that also to settle down as well.....



Have a reputable shop test the alternator with a saber machine or equilivant....



as stated best thing to do is disconnect the alt over night and go from there...



ALSO if a diode is bad, Some times the alt is WARMER then the rest of the engine in the AM from the drain....



Todd Z
 
l1tech,

I have never heard that Ford's do not shut down everything when you switch the key off?? What is the purpose for that, and why does it take up to 45 minutes to complete the shut down?



I know that some things like radios, clocks and some other electronic devices like alarms and remote locks require a small amount of battery power while the ignition is off, but what else is using battery power for 45 minutes after the key is shut off??



I know that some cars with electric fans can have the fan run for a few minutes after being parked, but nothing close to 45 minutes.



...Rich
Click to expand...



Pretty much all modern day vehicles keep some of the systems in a reduced power mode once the key is shut off, I am not an engineer so I don't know the exact reasoning behind it but I think it has something to do with the systems coming back online faster when we run errands and such and the car is not parked for a long period of time. Fords are the worst as they stay on for up to 45 minutes, GM I think times out after 10 minutes and Chryslers time out after 40 minutes. This trips up alot of so called techs because they end up chasing their tails looking for a draw when in actuality the system is operating as designed.



It's funny because we get vehicles in all the time with new batteries and alternators and the customer states that XYZ auto parts tested them and said they were bad but 2-3 weeks later the battery is dead again, sometimes the draw is easy to find...sometimes not so easy...I once had GM truck that took me 4 days to figure out adn finally found the draw after pulling the headliner out...there was a Lojack installed and it was wired up wrong so the system would time out but then wake up immediately...would have been nioce for the customer to tell us that they recently had the Lojack installed
 
Maybe I did it wrong, but. I used my ampmeter. My trac stops drawing any significant current after 10 minutes. I suspect the residual is for the ecu and radio presets.

Dont remember the current reading. Makes me want to checkagain. curiuosity killedthecat.



"DISCLAIMER, ALL THIS INFO IS POSIBILITIES"

 
The battery is an Optima Red Top. I installed it about a year ago. It's not completely discharging overnight. It's been happening if the Trac sits for a couple of days or more. For example: I drove the Trac last Friday, but it then sat in the driveway until Sunday evening. When I tried to start it to run to the store on Sunday night, the battery was dead.



I already bought an alternator last night, but haven't yet installed it. I'll disconnect the positive battery cable tonight, measure the battery, then measure it again in the morning to see if there's any change in the battery.
 
Disconnect the NEGATIVE CABLE !!! NEVER the positive first.....



Electronics are hurt by that.....

Also optimas can fail like any other battery



Also
 
I always remove the ground first, but thanks Todd.:supercool: After 20+ years as an electronics technician, I do remember a few things.:banana:



And I'm wasn't inferring that the year-old Optima battery couldn't have failed. Hell, I've had things like that bad right out of the box before. But a six-year old, 109,000 mile alternator seems to be a more likely suspect.
 
EddieS'04,11/16/2010 08:11 MT



Maybe I did it wrong, but. I used my ampmeter. My trac stops drawing any significant current after 10 minutes. I suspect the residual is for the ecu and radio presets.

Dont remember the current reading. Makes me want to checkagain. curiuosity killedthecat.



"DISCLAIMER, ALL THIS INFO IS POSIBILITIES"
Click to expand...



The systems will shut off in stages. Usually after about 10 minutes system draw is down to around .100 milliamps. When the system completely goes to sleep we like to see about .020 milliamps. Anything over .050 milliamps after the system has timed out adn depending on the state of the battery can casue a dead battery overnight, if it's a good battery then about 24 hours or so before it goes dead.
 
OK, after I got home home tonight, I disconnected the battery (both terminals), and measured 12.13VDC across the posts. I'll measure it again in the morning to see if there's any significant loss in voltage. If not, I'm replacing the alternator.
 

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