charge!
Senior User
Joined: Oct 2004
Posts: 371
Likes: 1
From: Wetaskiwin, Alberta
Check your voltage accross the battery posts with the engine at idle. The alternator should be putting out approximately 14.5 volts or so. If not then I would think that the alternator is failing. When you say it discharges do you mean a really big downward sweep of the needle or does it fall just a little?. What do you have running for accessories when you notice the discharge condition - headlights, heater, power hungry aftermarket audio system etc. etc. Is the battery holding it's charge OK or does it go flat after a few days or less? Could you "borrow" a known good alternator from a same or similar truck and see if it works better? You might also take the alternator to a good repair shop and have them bench test it for ya.
Post back with some more details - don't R&R the alternator until you are sure that it is the probelm and not something simpler like corroded wires, bad connectors or something like that.
Cheers!
Mike
Post back with some more details - don't R&R the alternator until you are sure that it is the probelm and not something simpler like corroded wires, bad connectors or something like that.
Cheers!
Mike
Thread Starter
|
Senior User
Joined: Dec 2006
Posts: 237
Likes: 0
From: churchville, ny
i going to pull the alternator tomorrow and take to autozone. when you first start it it will charge ok. when you stop it discharges to the point that the head lights die way down. guage goes almost to bottom. i'll keep you posted.
Thread Starter
|
Senior User
Joined: Dec 2006
Posts: 237
Likes: 0
From: churchville, ny
i didn't take it to be checked yet do to the weather, but checked at idle nothing on, got 14.5 across battery, turned on headlights and fan dropped to 12.5 at idle, would pickup to 13 when idled up. however while driving with everthing on would drop way down headlites go dim. should i replace alt. or get checked? i never had this problem with my other fords.
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
What does your battery voltage read (with voltmeter, not dash gauge) when the truck is OFF? If it's less than about 12.5V, then your battery could be bad or severely discharged. It's not recommended to charge a dead battery off the alternator.
Jason
Jason
Trending Topics
Thread Starter
|
Senior User
Joined: Dec 2006
Posts: 237
Likes: 0
From: churchville, ny
battery is ok. i think there's a bad ground or something that i can't find. if the weather permits tomorrow i'm going to do some further checking.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Freshman User
Joined: Jan 2007
Posts: 36
Likes: 0
did anybody try just changing the voltage reg. from a 95 amp. to a 130 amp, would it work?
You need to find the cause to fix the result.
I would agree with the possibility of a bad ground. Sometimes resistance isn't bad enough to be noticed until a large enough load tries to pass through, like corroded battery terminals or a ground.
Another example could be bad plates within the battery. A battery could check out ok with a multimeter but be bad when a load tester is put on it.
That would be my next guess to check after the grounding straps if you haven't already.
Any autoparts store should check that for you.
Freshman User
Joined: Jan 2007
Posts: 36
Likes: 0
Did you do or have someone, somewhere do a load test on the batt? Do you know someone who has a spare batt or may let you give theirs a try instead?
If you did all of that you may have a short somewhere that will take testing different circuts for amprage draw when they should be off.
Good luck.
If you did all of that you may have a short somewhere that will take testing different circuts for amprage draw when they should be off.
Good luck.
New User
Joined: Jan 2004
Posts: 21
Likes: 0
I'm having the same issue with my '90. It's not the alternator and it's not the battery. I recall reading a post on here about a wiring connection but i can't seem to find it. I'm thinking it has something to do with the voltage sensing wire that goes to the regulator. Probably a connection somewhere in that ball of wires on left inner fender.
Thread
Thread Starter
Forum
Replies
Last Post
oldbird1965
1994.5 - 1997 7.3L Power Stroke Diesel
19
Apr 19, 2010 10:29 AM
dgalloway
Explorer, Sport Trac, Mountaineer & Aviator
5
Jan 5, 2005 08:27 PM