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Electrics Dead

robertc1024

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HALP - So I'm driving my other truck (2008 F150) to a gym meet out of town. ABS light comes on while going down the highway. I was looking at the gauges, and all of the sudden all of them are dead. The truck was still running fine. I pulled off and parked it. I tried to start it again and all I heard was "Click click click" like the battery was dead. The interior lights seemed pretty dim too. I popped the hood, and the little green window on the OE battery was green with a little spot in the middle.

Questions:
Are those little green indicators are worth anything in analyzing battery condition?

If my battery just took a poop, would my truck act like that? I would think the alternator would keep things going unless it went dead open - which it didn't since the interior lights still worked?

Any other ideas?

I just left it in a parking lot about 30 miles away and fortunately my wife hadn't left home yet and the crew going to the meet grabbed an extra car. I didn't have much time trying to diagnose - Ranger to the rescue tomorrow.
 


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The green eye doesn't mean a whole lot.

I would check the batteries neg. terminal.
But I would be prepared to jump it or replace battery.

The ABS light can come on if power for the speed sensor is cut, no signal = dash light

The alternator has one wire that runs to the "charge light" or ammeter, it also supplies power for the ABS system and probably dash gauges.

This is from a Ranger 4.0l truck, charging system diagram
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_1.JPG
it is probably similar to all Ford charging systems.

I would also have a voltmeter to test battery voltage, needs to be above 12.5vDC
And after engine is started battery voltage should be at 13.8vDC-14.4vDC from alternator.
Turn on all lights, Fans and anything else that draws power, voltage at battery will drop but should come back up to 13.6 or higher, but no higher than 14.4vDC

Alternators work using 3 "fields" in the stator, each provides it's own AC current to 3 sets of diodes that convert AC to DC.
1 or 2 of these "fields" can fail, this of course drops the power output and over time the battery will be providing extra power.
The battery eventually runs out of power, this can take a few weeks depending on how much night driving(headlights on) you do.
Diodes and the voltage regulator can fail as well, this can blow fuses or drain battery.

If you ever notice headlights dimming while idling then most likely 1 of the "fields" has failed, the other 2 fields are running at max. via the regulator but can't keep the voltage above 13.6vDc. This usually won't drain the battery much since you don't idle long, higher RPM will charge the battery enough.

Lights dimming while idling is not "normal", lol, I have read that.
No manufacturer would put in an alternator that didn't have enough amps at idle to maintain proper voltage.
Now if you have installed a 5,000watt amp and/or aircraft landing lights then all bets are off, :)
 
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robertc1024

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Excellent advice as usual from you sir. I rarely comment on technical issues because although I understand how most systems work, I rarely know the specifics for the Rangers. It's never failed me. I've got some tools and the voltmeter loaded in the Ranger-Rescue vehicle which is going to be put into service tomorrow morning. The 3 fields thingy is new to me - never heard of it before. I hope it's just a dead battery and not the alt. I had to buy a new battery for the Ranger a few months ago, I was flabbergasted about how much they cost these days. I went to the autoparts store thinking I'd spend 50 bucks and it was a lot closer to 100.
 
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Keep hoping against hope on that alternator thing there Bob.

Postin' from teh Galaxy
 

robertc1024

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Update: So I drive the trusty Ranger 34 miles to see what's up with the F-150. I put the key in it, starts right up - cranked strong like the battery was fine. So, I drive it home. All gauges hot, straight and normal. I pull off of the freeway and the battery light turns on. Charging meter is perfect - all of the gauges look fine. After I get home, I pop the hood and battery voltage (truck off) was 12.40 V. I re-started it and battery voltage was 12.03 with nothing on, then I turned on all the lights, A/C, radio etc. and voltage was 11.44. Yank alternator?

The one thing I thought about that I didn't mention is that it was very, very lightly misting yesterday. It's only been a central TX truck and only has 62k on it.
 
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Yes, something in the alternator is not working most likely.
But I would check voltage at the B+ connection on the alt.(big wire) while engine is running, ground meter to alt. case.
Long shot is that fuses are blown so alt. power is not making it to battery, if you have 14vDC at the B+, that could be the case...........but what blew the fuses would be the next issue, over voltage on the alt.?

12.4vDC and less measured on the battery could mean the end of that battery.
At 5 years old it's about due to fail anyway, the fact it recovered after sitting is a good sign but it is still close to the end of it's service life.
 

robertc1024

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Engine running, no accessories 11.80 V from big terminal on the top to case. Lights on etc. 11.44 V. As far as the 100+ fuses go, all the reasonable ones I pulled were fine. Smells like alternator to me. If one of the diodes went bad in the rectifier(s), are they replaceable? I've done it before.
 

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Are you certified in electronics repair? Generally the rectifier/regulator is considered a non-serviceable part. But this doesn't sound like a bad regulator to me.
 

robertc1024

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That's kind of non-committal dude (it's supposed to be a joke.) What does it sound like? If I had an oscilloscope on hand, I could give you more detail. I can nab one at work tomorrow and give more info.

Certified electronics tech, no, just a lowly mechanical engineer. But I work with three electrical engineers that know their stuff backwards and forwards.
 

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Sounds like a bad alternator.
 

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Engine running, no accessories 11.80 V from big terminal on the top to case. Lights on etc. 11.44 V. As far as the 100+ fuses go, all the reasonable ones I pulled were fine. Smells like alternator to me. If one of the diodes went bad in the rectifier(s), are they replaceable? I've done it before.
Alternator is drawing power from the battery, it is dead.
You can buy the electronics for most alternators but you would still have the old bearings and other internals.
Local shops can do full rebuilds, but it is usually cheaper to buy a rebuilt from an auto parts place.
Wrecking yards also test and sell used alternators.
 

robertc1024

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Thanks guys - I'm gonna pull alt. We've got a pretty good place in town that re-builds all kind of electrical stuff next to an excellent Mexican food place. Sounds like lunch.
 

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Well....just so happens....my battry has been getting weaker lately....

BUT......Alternator is putting out 13 to 14 volts engine running.....

removed negative cable connected voltmeter from negative battery post to frame...

6.0 Volt parasite-draw

draw on voltmeter drops to 0.0 V when I remove ALT. fuse.....AAAAAhaaaa!


"the oil cans are DEFECTIVE!!!!!!!"
 

robertc1024

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POOP - After i got home from work, charged the battery 4:30 to 9;30. Took the truck to Autozone and they clipped their thingy onto the battery. Said it was bad. "Sir, Start your truck. oooh - you got the double whammy." Alt and battery are dead. You're alt is pumping out 7.5 volts. Ay-Yi-Yi $350 easily because I'm going to replace the serpentine belt at 62K. Stupid cars/trucks. They only exist because you're not where you want to be.

Thanks for the help though. +Rep to RonD, No rep to Adsm & DG. gotta spread it around.

Edit - Adsm gets some loving too. Sorry DG.
 
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An old way of checking the alternator is to take a metal butter Knife and touch it to the back of the alternator on the end of the shaft with the motor running. if it sticks or feels like metal to a magnet it was good. At work we use an old analog tester it does a better job than the new digital testers.
For a battery I went to an Interstate battery center an bought a refurbished battery for $45.00 with warranty. Or check your local junkyard some cars were junked with new or nearly new batteries.
 

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