Alternator Issues?

[JFulford]

I've got an 03 Dodge auto 4x4. No extras(other than brake controller). I purchase (2) new batteries almost 2 years ago. The truck is mostly a home business truck, so it has extended sit times(2 weeks in this case.

I got in it the other morning(25 degrees) and no go(solinoid yelling, etc). Batteries at 12. 0. Charged all day and the truck fires right up in 22 degree weather, no heater. While watching my multitester and my charger, which has an

alternator checker, it seemed to me that when the grid heaters kicked on, my alternator turned off(14 volts or so, to 12. 5 then back to 14 volts) with my charger alternator check telling me 0 when this happened.

The vehicle has 120K on it. Do I have a failing alternator or is this normal behavior? The batteries do not seem to have failed(after the charge).

jeff

 

[Prairie Dog]

No, the alt can't keep up with the grids which take about 150 amps. During this time the volt meter can take a dive. This is not to be confused with the time in which the V. meter is disabled right after start so people aren't alarmed by the dropping voltage.

What your seeing is normal. If the trucks sits long enough the parasitic loads will deplete the batteries. However, mine sits for as much as 2 weeks and still starts although we don't have to contend with extreme cold.

 

[JFulford]

Prairie Dog,
Thanks for the info. I was hoping that what it was. I just didn't understand how quickly parasitics may have drained the battery. Got a solar charger plugged into the cigarette lighter now.
jeff

 

[Prairie Dog]

What kind of batts did you get? Many have bought the coil-AGM type only to find they lack capacity and it shows up when it gets cold outside.

 

[JFulford]

I've got(embarrased) Duralast Gold--3 year full replacements. I was in a hurry(leaving the next day) and one of my originals crowbarred. They were about $70 cheaper(per) than the agms.
jf