2008 3.0L Ranger V6


Driving home two weeks ago and battery light came on 2 hrs into a 4 hr drive. Pulled into gas station when stereo light began flickering and headlights dimming. Shortly after, lost all light and power, but engine stayed on.


Got a ride from my folks, and next day girlfriend drive me to the town I had to leave my truck in. Bought new alternator and battery, put em in, started truck and was good. No battery light. Drove home.


1.5hrs into 2 hrs home, notice my gauges are dead. Lights are on, and dash bulbs working, but my gaugues are reading zero. I stop at a red light and they come back . . . I accellerate, and they die. Battery light returns.


I park truck at home, decide to work on it next day. Next day, wont turn over. Battery is reading 0.64 volts.


Get a new battery under warranty, replace friewall groundwire, clean other visible grounds, plug battery in. It's 12.5. Start truck, it's reading 19 volts! I kill the engine, and battery is reading 13 volts. Turn engine on, drive it around the block. Same instrument cluster problem. Dies on accelerating, comes back when braking or foot off the pedal. Battery light comes back.


Next day, I get alt replaced under warranty, thinking the overcharging is ******* up the ICP. I change alternator, go to test battery, and it's dead . . . new Battery, a day old, only had engine on for 30 mins max day previous. Reading 5v.


I have no clue what to do. Fuses? Relays? Parasitic draw?


Any help is appreciated.


PS, few months ago I changed my gear shift indicator assembly. My uncle thinks a wire was damaged behind the cluster, but I hadnt had problems at all after for some time.

 

Welcome to the forum

I assume the new battery the first time had same battery terminals, + and - in the same place as the old one, so they were never reversed

Lets do a quick wiring test
Key OFF
Battery volts, 12.3v to 12.8v is OK, but remember it
On the alternator is B+ terminal, stud/nut terminal, test it to alternator's metal housing, should be exactly the same volts, if lower then retest to battery negative, if at battery volts now then engines ground cable from battery negative is loose, bad
If very low or no volts on B+ then a fusible link is blown

Unplug 3 wire connector on alternator, test Red wire to alternators case, should be Battery Volts, if not fusible link is blown
Test Grey wire to alternators case, should be 0 volts
Turn key on, engine off
Retest grey wire should be almost battery volts, because with key on battery voltage will drop slightly(this is the Battery Light wire)
If still no volts then check fuses 9 and 10 in cab fuse box

If everything tests OK then plug it back in and start the engine

Retest battery volts, 13.8v to 14.8volts is OK
If still battery volts then alternators is bad, some people have had to go thru 3 NEW alternators to get a good one, just FYI

On the positive battery terminal there should be a larger cable going to start motor and then a smaller wire going to engine fuse box, ALL vehicle systems are powered thru that one smaller wire when engine is off
The alternators B+ wire connects in the engine fuse box at the same place as the battery's smaller wire, via Fusible links
When engine is running all the vehicle's systems are powered by this one B+ wire and battery is charged thru its one smaller wire because it hooked to the B+ wire

2008 charging diagram below

The Negative battery terminal and its wires need to pass the same voltage/amps as positive, electricity need a circuit(a circle) to power anything, so a poor ground/negative connection is exactly the same as a poor 12volt connection, it limits the volts/amps that can pass thru it


Loose connection causing systems to shut down
If just lights or gauges that are effected then its going to be a bad connection
Main headlights dimming at idle is an alternator issue, not working at all or bad field
Dash gauges failing can be cab fuses loosing connection
2008 has an SJB(smart junction box) as its Body Computer, these can get corroded connections, known issue

SJB is behind the passenger side kick panel, looks like this: https://www.therangerstation.com/tec..._project-5.jpg
Cab fuse box is part of the SJB

Because of its location it can collect moisture and get corrosion, in the fuse holders and the 4 large connectors
Seen here: https://cimg9.ibsrv.net/gimg/www.ran...82fcc20c13.jpg
And here: https://i0.wp.com/sparkys-answers.co...0/DSC09930.jpg

Its not "common" just a known issue

But its a place to start, pull the kick panel, each connector will have a lever you pull up on, and that will push/lift connector away from SJB so it can be removed and inspected, do all 4
This also cleans each connection when its pushed back on, so not a bad thing to do

You can also unplug and plug back in each fuse while there

Engine bay fuse box has Main Fuses so you would expect to lose several systems at once if there was a loose/bad connection in there, but could happen, unplig and plug back all the fuses and relays

 

Hi Ron, thanks very much for your reply. I've been googling this issue and been on the forums, decided to make an account and ask. Saw your name loads on other threads, was hoping you'd see mine, hahaha.

I'm going to charge my battery after work today and run these tests you suggested, also look for a parasitic draw. Don't understand how it went from 12.5 to 5 volts overnight without truck being on.

I did start taking out the dash to have a look at wires and I also removed the cover to the SJB, I but it was dark and I don't have a garage. May have to wait till I'm off on Monday to do it during day. That being said, I live in Canada and my Ranger does struggle with rust like many vehicles here because of the winter (Ontario).

Didn't think it was fusible link because no resistance from red alternator wires to battery, stud or the one in plug to alternator. The 2 red wires going unto engine fuse box are bolted in place and those are rusty . . . Relevant?

Can't do much testing till I charge battery but am very nervous about having it drain overnight again.

Truck is used and have had since April. There is a remote starter installed. Thanks again!

EDIT: Forgot to mention, when i had first installed the new new battery (after new one died) after replacing firewall ground and cleaning other grounds (firewall passenger side, and one above left headlight inside engine bay), i checked volts from alt to batt and it was reading the same as just the batt (way high, like 17volts.)

 

Alternators should never go above 15volts, so bad regulator in the alternator
Just FYI
The voltage regulator feeds 7.5 to 9.5volts to the rotor(part that spins)
This creates a magnetic field around the rotor
In the case/housing of the alternator there are 3 separate Field Coils
As the rotor spins its magnetic field causes AC voltage to build up in the 3 field coils, each field has 2 diodes that change the AC in to DC Volts
7.5v to 9.5v IN to the rotor generates 13.5 to 14.5v OUT on B+

If the voltage regulator sent 12volts to rotor then alternator could generate more than 15volts easily, but that of course would cook the battery and "maybe" some of the electronics

Unhook the battery from the vehicle next time, test its voltage, write it down
Come back after 4 hours, or over night, and retest, if its dropping then battery has an internal short, for sure, bad battery, a battery can sit for years and not lose a volt

Drain test can be time consuming, well 30-60min, lol
Newer vehicles stay "awake" for 30-60min after key off doors closed
So key off doors closed, unhook negative battery cable and hook up the AMP meter between cable and terminal, AMP meter needs to STAY connected, so clamp it to battery terminal and cable end
The vehicle's systems need power thru the AMP meter so its timer can count down to "sleep" mode
Look at the meter should be 1-2 amps
Then wait......................
Check it after 30min see if its has dropped............................
Once its dropped it should read 0.07amps, 70mA(milliamps)
So under 0.10 amp, 100mA
That's the computer, radio and Keyless entry amp draw in "sleep" mode
If no keyless entry(Fobs) then 0.03amps, 30mA is expected

If you still have a working Hood Open light, pull out the bulb or unplug the connector

 

Hey Ron,

I had a brand new battery in, and the new alternator was charging it at 19, then 17/16. Next day battery was 5v.

I'm charging it at work right now. Reading 12.4 after a few hrs. Gonna run tests tn. Yesterday i had my alternator replaced under warranty for over charging. Hoping this one is good. Will bring battery home and put in truck and test Volts before connecting.

 

A lot of posts these days about bad alternators "out of the box"
Seems WE are now the Quality Control Department for most part makers, lol
They just give us a warranty and WE test it for them

So never ever trust new parts

Ford and other car makers insist on some testing(Quality Control) before shipping, and you just need to look at the price of Ford parts to see what that testing costs, lol
Labor to test parts is expensive, but that's the choice we have, if its a hard to get at part, like a fuel pump, I would get Ford part even at 3 times the price of 3rd party

WE are basically FREE labor to other parts makers, lol

 

Well, I think that's what it was. Charged my battery at work, brought it home, plugged it into the truck, (and 2nd new alternator) and did all the tests you recommended in the first reply. They all checked out alternator-wise indicating no blown fusible link or wiring / fuse issue. I turned the truck on, it turned over. The gauges were giving me readings off the bat, no battery light, and I tested battery, it read 14.8v. I let it idle, waiting for any codes, none. So I took it for a spin and it wasn't losing power to the cluster when I accelerated like it had been.

Went to check for parasitic draw and blew the fuse in my multimeter in excitement . But on the 200ma (2 fuses, blew the big one) setting no indication of draw. Will test again later but just happy to be able to drive to work. Will definitely find all grounds that I can and clean em, and do a full electrical cleanup / rundown. Thanks so much!