Hi everyone and thank you for your help in advance! I'm having a drain issue that has a few people/mechanics stumped.
To start i have a 1996 F250 with the 460 and E4OD transmission. This last month i have been having a slow crank issue but the truck would ultimately always start. then i took a 100 mile trip down to Sacramento from Reno parked the truck for about 2 hours went to start it, it would barely crank and would not start. i couldn't get it to jump start (however i was using a 2015 v6 mustang) either way i ultimately had the battery checked at autozone it came in with 55% charge. They took it in back tested it and charged it. they said it was good and now 100% put it in the truck and had no change. So i moved on to changing out the starter and starter solenoid. this helped a little to speed up the crank but it was still moving to slow so i had them switch the battery out in case it was a false positive the truck started instantly so i drove home (reno) about 100 miles back and had no problems what so ever. parked it and went to start it about 5 min later to have the same slow crank and no start. luckily i was able to put a trickle charger on it and charge it back up, the charger said it was at 55% charge. once the battery was at 100% started it up and checked with a voltometer which read 14.5v while running. but once i turned it off had the slow crank again. i have since tried cleaning up all connections and check all wires which all look good and solid now but no change.

So in recap:
-New battery
-New starter
-New starter solenoid
-cables look good
-Connections look clean
-alternator is less than 4 months old
-transmission, coolant, oil all look good.

Any ideas to point me in the right direction?

 

Based on what you've stated 4 month old or otherwise I'd suspect your alternator as the problem, bad diode/s in the rectifier causing parasitic drain on the battery even though it charges when running.

Pull it off, take it back to where you bought it for exchange.

 

Is there anyway to have it tested to be sure? or just have to put it on and see if it works?

 

To add to what Danr1 said, check to see if alternator is warm or hot to touch, after setting awhile or overnight.

Measure for parasitic load or draw with ammeter in series with either battery post and a cable. Compare with alternator connected and disconnected if this is a suspect.

50 milliamps is considered OK, at least in modern vehicles. 1000 milliamps = 1 amp

 

1. Put a voltmeter across the terminals of the battery. Read the voltage. It should be AT LEAST 12.5 volts after sitting overnight. (the real number is 12.6V, but I'm giving you a tiny bit of leeway.) If it's below that, then you either have a bad cell in the battery, something is draining the battery, or the battery is leaking internally.

2. Assuming the voltage is good, start the engine. The voltage should be maintaining 12.5 or better at idle. Many newer systems should pop the voltage up to more like 13.2 to 13.5 volts at idle, but not so much on older vehicles.

3. Rev the engine up to 2500 to 3000 rpm. The voltmeter should be reading 13.2 to 13.6 volts and charging the battery. If it's not, that is likely your problem. If the voltage is below whatever your voltage was in step two, your engine is drawing power from your battery and your alternator is the likely culprit.

4. If all that is good, remove the battery, put it on a charger for 30 minutes big charger, or 2 or 3 hours for a trickle charger. Remove the charger and read the voltage. It should be over 13 volts immediately after you remove the charger. Let it sit for 15 minutes and read it again. Let it sit overnight (without the charger) and read it again. It should always read 12.6 volts or higher, or your battery is leaking internally.

5. (and this is high on my list of suspected problems) Finally, if all the above is good, I would check the ground strap that runs from the negative battery terminal and typically bolts to the engine. Unbolt and pull the strap free of the engine and inspect the terminal at the engine end. Clean it and clean the engine with a wire brush. Measure the resistance of the strap from one end to the other. It should be a small fraction of an ohm. If it's ok, get some battery terminal grease or CRC battery terminal spray from the auto parts store, apply the protectant, and bolt it back up.

 

Take the truck to your local battery dealer,or parts store. Have the starting charging system tested. They will do this for free in the hopes of selling you a battery but will give you a printout of the health of your starting charging system. Guessing with parasitic draw is silly. The multimeter approach will confirm a draw but is a little more involved to test your own starting charging system. Hope this helps. My parasitic draw was the DRL, as it is not connected to the fuse box, fused right off the battery...

 

Thanks for all the replies i pulled out the alternator tonight and will change it in the morning. since its under warranty it should be easy to swap. hopefully it is just a bad alternator and i don't have to dig farther into it. ill keep y'all posted on it tomorrow

 

sorry for the delayed response, its been a busy week. i ended up swapping my alternator and the harness for the alternator as well after having a shop test the systems. the shop determined it was a bad harness which wasn't letting the alternator charge. unfortunately its still not running.im just glad i did the work they wanted $700, i did it for $140.. im going to try and get it to another shop that can hopefully figure it out its starting to snow here and need the truck!

 

Yep, people balk or their eyes glaze over at paying $75 for a good DMM (that will last 25 years at least, and is used for all kinds of stuff, not just trucks) but then get all butthurt when the shop charges $750 and may not have solved the problem. It's a mystery.

 

Check that the lt green/red wire at the alternator has battery voltage with the key in 'run', engine off.
If not, check the charging system fuse.