Ive been having this problem lately where my batteries will drain overnight and the truck wont start in the morning. I went and had the batteries checked and they tested good, we tested the alternator and it was toast so i replaced that and still acts the same.
What could be causing the batteries to drain like this? the battery gauge on the dash reads good the headlights don't really dim at all either, if i hook the jumper cables to it, it fires right up
Maybe a bad connection or short somewhere between the battery and alternator?? or battery and starter???
95 F-250 ext cab lwb 4x4
custom tuned TW chip
DIY electric fuel
Valair ceramic clutch
4'' straight pipe
Dana 60 conversion in progress
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You may have a short or a parasitic draw and you can check which circuit by using a 10 dc ammeter. You disconnect the negative battery cables and then hook the test leads between the negative cable and the negative battery post and read the draw. If there is a draw of 35 milliamps, or .035 amps or higher then you have a problem. First thing is to remove the alternator heavy cable to eliminate the alternator. If still a draw then remove each fuse one at a time until the draw is gone and then you found what is draining the batts.
Okay, this is my first post and I don't have much time right now but....
I had this battery drain problem recently and found that the glow prug relay was continuing to power the plugs. I replaced relay with the White-Rodgers? part that was recommended here, I think. No fix. Then, I saw that the PCM is supposed to drop a ground after some calculated time to turn off the relay so, I removed the PCM thinking it might be the problem. I found that the cable connection to the PCM had some corrosion/oxidaton on some of the male pins and some female holes so, I cleaned them up...small wire brush on pins and a push pin in the holes. Reassembled and...problem fixed! I am a happy camper.
I hope this helps someone as I appreciate the help that I have gotten here. You guys put me on the right track. I will check back later to see if you have any questions.