Dead F150

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1994 F150 with 5.0 auto 4x4. Battery was completely dead, would not even light the test bulb. Changed the battery and that new one is now dead the next day. Everything was off and the key was out of the ignition. Now these 2 batteries are completely DEAD! No amount of charging helped in the least. So dead U couldnt even get a shock from it wearing a wool suit and balloons. What would kill them overnight?
 
The Alternator. This has a 2G alternator, correct? She's probably shorted internally. I've had two Ford alternators of that generation do exactly what you've described.
 
Charge up the battery, get the truck started, and measure voltage at the battery with the engine running but everything else electric turned off. It should be in the high 13s to low 14 volt range. I don't think a 1994 would have a smart charging system. If the voltage stays in the 12s, the charging system is not working and the battery is going to eventually run down.

If that is OK, alternator is working but something may be draining the battery while it is off. The test for this is to disconnect one terminal from the battery then connect an amp meter between the truck and the battery. If it's a heavy draw you could use a 1156 bulb. The bulb should not light. If there is current draw, start pulling fuses and disconnecting stuff. The alternator would indeed be suspect. The alternator's big output wire is connected directly to the battery, so it is live when the key is off.
 
Kinda wierd that when the charger was on it read 0.0. Even on boost to start I got nothing, and I mean nothing. No sounds or lights anywhere. U would thing the booster would do something at 100amps.
 
What kind of charger are you using? A newer smart charger will sense that something is wrong and won't try to charge.
 
Last edited:
Originally Posted By: ridgerunner
Most likely a “smart” charger.


If this is a 2G alternator, it should just have two plugs on it. Unplug them and then try and charge the battery.
 
Ok I will give it a shot tomorrow. If it charges then dies again then it is the alternator?
 
You may need to jump from a charged battery or another vehicle to get the battery off of "dead flat" before the smart charger will pick up. Don't start either engine just hook up the jumper cables and let some charge transfer over. Then connect the charger also in parallel and let it charge both for a while.
 
Last edited:
Originally Posted By: ridgerunner
Ok I will give it a shot tomorrow. If it charges then dies again then it is the alternator?


Yes. But I wouldn't subject your battery to that again, it is pretty hard on it.
 
Decided to try it now. Pulled cables off of battery and now the charger is working. Says 6.4. The charger is a cheap Shumacher 100amp from Walmart. New alternator then?
 
Find an old charger and use that for several hours then connect up the smart charger.

Or jump good battery to dead and apply smart charger.

When you put the battery back in after charging, don't start the car, wait for a few hours and feel alternator to see if it's warm.

Checking the alternator to be warm might not be a good test in the winter cold.
 
Originally Posted By: ridgerunner
Decided to try it now. Pulled cables off of battery and now the charger is working. Says 6.4. The charger is a cheap Shumacher 100amp from Walmart. New alternator then?


Yeah, that's a pretty solid indication the alt is shorted. Do you have a multimeter? You could test it.
 
Any good alternator has to push the battery voltage to over 13V (to a typical max of 15V) if it outputs anything.
Vehicle systems need alternator power, not battery power. The battery should only be charging or floating when the engine is running.

If the battery voltage does not jump, then the alternator is dead. If you shut the engine down and remove
a battery cable and put a DC Amp meter in series and see any current over .030A then you have shorted diodes
in the alternator, if anything you could see 1A to 5A with a shorted alternator, thus killing your battery overnight.
 
Often older alternators on good vehicles get a diode damaged when you use the good vehicle to jump-start a vehicle with a bad battery while the engine (and alternator) on the good vehicle is running. If you have recently (within the last couple of weeks) jump-started another vehicle while your vehicle was running the load of the bad vehicles starter may have drawn enough current to damage a diode on your alternator and that damaged diode will draw current and discharge your battery when your engine is shut off.
 
When I had a problem with an alternator draining the battery, after the car had been sitting long enough for everything under the hood to cool to ambient temperature, the alternator felt much warmer than the engine..which is how I knew the alternator was the problem.
 
I removed the battery cables last night and put the charger on it while it was unhooked but still in the truck. Worked like a charm. Battery was trickle charged all night. Hooked battery up again and truck started. Ordered a new alternator last night from Rock Auto. Gotta tell ya, U guys R awesome. Thank you all very much!
 
Of course until you know it is fixed, disconnect the battery when not using the truck to prevent killing the battery again.
 
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