Heres the deal sometimes at startup about 10-15 seconds running the battery light will come on for 10 seconds or less. at this time i am able to monitor with the scangauge 13.0 volts during the time that this is happening. no problem other than the light on dash 10 seconds or less only sometimes. terminals on battery are clean. so could it be a dirty connection somewhere else? batterys were replaced dec 2009 alt replaced reman motocraft jan 2010 bad battery again have a digital multi meter will try to check load on batterys tomorrow. what eles do i need to check. thanks for all you guys help on this FTE has been a great resource. Iv saved alot of money with the help from the members from the site thanks everyone

 

Check all the grounds on the block. Check and see what the battery voltage is after the truck sits over night. If below 12.5 , seperate the battery gnds. and see which battery is pulling the other one down. My batteries are at 12.75 after sitting overnight. Just a place to start. Also you wouldn't be the 1st person to have a rebuilt alternator go bad on them.

 

Also, don't rely on voltages until the glow plugs shut off.....altho that shouldn't make the light glo or flicker......

BTW, you can not check the load on the batteries with a simple DVM. Take it to a battery store or garage that has a REAL load tester.

 

Correct, my voltage check was just to see if you have a weak or shorted cell. It is a no load test.

 

i got a battery hydrometer today. has anyone used one of these it was really cheap. I know the load test at the auto store is still probably the best but is this hydro meter any good

 

i need a better alt for shure you can crank the stereo up and watch it drain the volts on the scangauge anyone have a high output alternator where can i go to get a good one

 

What kind of stereo? Is it stock or some aftermarket high power thing? Voltage is only part of the equation. You can have voltage, but without amperage it's pretty much useless. Think of your battery cables as a garden hose. Voltage is the force of the electron flow, or in layman terms the pressure in the garden hose, amperage is the amount of flow, or again in layman terms the amount of water flowing through your garden hose. The fact that your light is flickering leads me to believe that you either have a bad connection, but it would come on intermittently while driving and not just after starting. I had a similar problem, yes the reman alternator went. Burnt up stator after 6 months. Given that yours does it only after start up leads me to believe that it's your alternator. The draw coming from the glow plugs and FICM is pretty big and your alternator can not keep up - until they shut off. Now when you turn the stereo on, it isn't much of an electrical load as far as voltage goes, but it can draw a lot of amps. Hence the charging light coming on. The higher the stored amps in the battery, the higher the voltage between positive and negative. Drain the amps faster than the alternator can replenish, and your voltage will drop. The hydrometer will only tell you what you already know, that you have 13 or so volts depending on charge level. It won't tell you why the charge is low or high.