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Help! New alternator tests good but battery is dead
Savannah Buzz- are you out there? You helped me a couple weeks ago with my battery being dead and you were right - the alternator I replaced in January tested bad. I ordered a brand new one from BP Utah and installed yesterday and the battery was fully charged. Car was fine yesterday. This morning - dead battery. Swithced batteries with my boyfriend's truck and took to Autozone - battery tested fine and their machine said the alternator was charging the battery. Only problem showing on their machine was a starter problem but it starts fine. Also had them test the codes and showed no problems. No lights are on on the dashboard. Anyone have any ideas why my battery would be dead this morning??? This is a nightmare - really really need my vehicle for work!
Belt route is very important. Other little things include terminals clean enough to kiss, including ones on top of battery and the two large ones inside the underhood fuse box. You clean terminals WITH THE BATTERY DISCONNECTED.
But since you could crank the truck and drive around, you might also have a new problem, a drain in the electrical system that kills the battery after you power off the truck.
A great tool is a $10 - 20 voltmeter from Wal AMrt, Harbor freight, etc. If battery is being charged, volts across it will be 13.8 - 14.2 volts. One easy way to test with a meter is to measure battery with truck turned off. Let's say that is 12.9 volts. Don't crank truck, but turn on head lights. Volts should not drop below 11.5 - 12 volts. If you have a "dead cell" in a battery, the volts will drop like a stone under load. Then crank truck. Volts should come up to 13.4 - 13.6 with lights on, or a little higher. That proves alternator can charge the battery while also running a load (lights and rest of truck).
It is possible to have a fairly new battery that is defective and has a "dead cell". It is also possible to have something in the truck drawing current after the key is off, and run the battery down. This can cause real issues with the alarm system, which thinks Fortress Rover is under assult, and immobilizes the starter system....
Hoping you just have a belt issue, or left on some lights. If you park inside a garage or protected area, might consider leaving alarm off, and disconnect battery tonight to be sure you have a battery in the morning to get to work.
Hoping you just have a belt issue, or left on some lights. If you park inside a garage or protected area, might consider leaving alarm off, and disconnect battery tonight to be sure you have a battery in the morning to get to work.
Or hook up your battery charger and leave it charging all night and make sure you have jumper cables in the truck.
Thanks guys! Don't have an explanation but seems to be fine now. This is the second morning it started fine and I drove it all day yesterday. I am going to get the voltmeter and do the tests you suggested. Maybe I had left a door ajar but the dome light does not work and someone told me if it is broken it should not drain the battery...
I'm sure most people on here know a lot more than I do about "car stuff" but a word of warning/advice - I bought my alternator in January at Advanced Auto. Didn't know at the time how much better a deal I could get on-line or that I should not get re-conditioned. Anyway - after changing spark plugs, spark plug wires, etc last month we took out the alternator and took it back to Advanced to be tested even though it was only 8 months old. It was under warranty. They tested and said it was a good alternator - no problems. Luckily a co-worker suggested I take it somewhere else to get tested. Took it to AutoZone and it failed. They were very nice and printed me a report. Had to then take it back to Advanced and showed them the report - they re-tested and lo and behold - it failed. They had no access to a new alternator - all of their sources were re-conditioned. Had to go back to Advanced the next am again to talk to the manager and get cash back instead of store credit. Ended up getting a brand new one from BP Utah for the same price as the reconditioned ones.
Yup, I went through 4 rebuilt alternators in 2 years, 2 from AutoZone and 2 from Advance Auto, they are all junk.
I finally settled for a used one and that has lasted 2 years so far.
I returned my defective alt for cash back.
I am having a similar problem. My 2001 Disco would not start. It would turn over, just not start. Test the battery at Oreilly's and it was bad, so they said. I drove it about 60 miles and turned it on and off several times. This morning it would not start. But when I jump it, it starts. I checked the battery when it was off, 12V. When I started it, 14V so the alternator is charging the battery. I am at a loss. Any help would be great appreciated.
Your battery has a dead cell, so it can't hold up voltage under a good load. It will read normal charge volts, those electrons come from the alternator.
With truck OFF, read volts across battery. Then switch on head lights. Voltage should not drop by more than 0.5 volts or so. Head lights should not be way too dim. A battery with a dead cell will drop voltage quickly under load, head lights will be barely on, etc. Crank truck. Voltage should increase across battery as alternator charges up battery and keep up with the load.
Or you could have dirty terminals on the battery or the main fuse box. See big ones at front of fuse box. All terminal posts and conectors on them should be so clean you can kiss them. Don't wanna pucker up? Then keep cleanin'!
My battery kept draining overnight. We replaced the battery and rebuilt the alternator. After pulling fuses, we figured out it was the amp underneath the drivers seat
A good point, and another post found a "stray" drain from the sub woofer amp in the back door of a D1. Did you watch battery with a meter while pulling fuses? How did you determine which fuse was causing the problem?
Help! New alternator tests good but battery is dead
