Battery dying while driving

[JEyster]

2006 Expedition, first indication of trouble, panel started going wonky, speedo, tach and guages went to zero, then all went dark, a few miles later the engine died at a traffic light. Never saw the battery warning light prior to this. Swapped battery and got it home. Pulled the alternator, checked okay at the parts store. Charged the battery. Next day, short trips through the day, started noticing slightly lower needle on the guage, slightly slower cranking (no battery light). Got home, battery drained, just clicks. Recharged and had it checked, okay. Advice appreciated

 

[SafariGoneWrong]

I’d charge the battery, start it and put a voltmeter on the battery. You should see over 13.5 volts. If not, I’d suspect alternator regardless of store test results. Also, turn on headlights and heater/ac fan on high and see what happens. You should see around 13.5 volts if all is well.

If you want to go high tech, get something like an OBDLink MX+ adapter and run ForeScan Lite on a phone or pad. The PCM monitors alternator load and you can see what the PCM is thinking. I drive around a lot with OBDLink running on the iPhone and have a 2nd set of “gauges” to see how the engine is doing.

 

[JEyster]

My spare battery was in overnight to charge the primary. Drove to the parts store this morning to have it checked, started it a few times (spare battery) up until 2 hours ago, normal cranking speed. Came back to it a few minutes ago and the spare battery is now discharged, just clicks.

Disconnected the negative terminal, ammeter between the post and the clamp shows a 4.2 amp draw. Do I need to start pulling fuses?

Put the charged primary battery back it to check voltage on the battery with it running, lights and fans on, showed 12.0. Pulled the negative terminal assuming it would drain it again

 

[Hamfisted]

Lift your rear glass and see if the wiper arm moves freely when not engaged to the wiper motor cam. The rear wiper motor is a common draw issue if the wiper arm shaft gets corroded and hard to move, to the point the wiper motor can't get it into the "parked" position. It keeps trying, until it kills the battery. Other than that, look at it at night and see if you see any interior lights remaining on when they shouldn't be. But to kill your battery that fast it'd have to be something like the rear wiper motor. With the motor idling what kind of voltage are you reading across the battery terminals ? Should be something like 13.5 - 14.0 volts if the alternator is charging correctly. If it's only 12v like you said in your earlier post, I'd try a new alternator. Either a Motorcraft or NAPA brand. If your Expy doesn't have FACTORY Navigation package you only need a 110 Amp alternator, not a 135 or 150 amp.


2006 Expy Alternators at Rock Auto


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[JEyster]

The rear wiper moves freely. The alternator tested 14.5 volts at O'Reilly's however I've read to not take that to the bank. Ordered one from Rock, will be here Tuesday

 

[Al Steel]

My spare battery was in overnight to charge the primary. Drove to the parts store this morning to have it checked, started it a few times (spare battery) up until 2 hours ago, normal cranking speed. Came back to it a few minutes ago and the spare battery is now discharged, just clicks.

Disconnected the negative terminal, ammeter between the post and the clamp shows a 4.2 amp draw. Do I need to start pulling fuses?

Put the charged primary battery back it to check voltage on the battery with it running, lights and fans on, showed 12.0. Pulled the negative terminal assuming it would drain it again

Woah! 4.2 Amps draw, is that with the engine running or off??? If the engine is off 4.2A is a pretty hefty draw. That's definitely not any kind of single dome light, clock, stereo, etc. Do you have any aftermarket accessories installed that may be drawing that? CB Radio, aftermarket stereo amp, AC/DC inverter, etc? I'd unplug any unnecessary aftermarket accessory. Pull the fuse for them and recheck the draw. Like Hamfisted said, just to be certain, pull the wiper motor fuse. Also check for corrosion on your terminals, chassis ground connections too (rust, corrosion, loose), maybe check your trailer electrical connections. If you are drawing 4.2A with the engine off that's a big red flag. Something is puling that, maybe a blower fan motor, fuel pump, air suspension pump?

Battery voltage across the terminals with the engine running at idle should be 13.5-14.4VDC. Note that is reading the CHARGING voltage because the voltage is being supplied by the alternator. If it's not, something in your charging circuit is bad. With the car off and negative terminal disconnected, the battery voltage at the terminals should be 12.6VDC +/- .1 depending on the battery. If its above 12.8 its being overcharged, below 12.4 and it's going dead.

12.0VDC across the terminals while running is definitely low, that basically low battery voltage, charging system is doing nothing if it's only pushing 12.0VDC. It will be interesting to see if the new alternator will fix this. I keep going back to the 4.2A draw... IF that's with the engine off. Running is a different story. Running then that's a normal draw and it's most likely the alternator.