Just over the past few days, I've noticed it... When I turn off the truck, of course all the guages go to zero. But a few seconds later, they all drop way below zero, and then they flutter for a second, then they go back to zero (all this aftef the key has been turned off).

What does this mean?

On another (possibly related) note, I've noticed that the battery is getting weak. It still starts ok each day, but for example, last week I was working in my truck, had the key off but the interior lights on. After about an hour, they truck barely turned over (started). So I went to Kragen and had them test the battery. The voltage was 12.6v, but the CCA was only about 450 (battery is rated at 650 CCA). The lady (assistant mgr) said normal voltage and low CCA means the alternator is not charging correctly. That doesn't make sense to me...

Anyway, are these 2 problems related? Is it my battery? My truck is a 2005 model, with about 48,000 miles on it. Everything we're talking about here is original.

 

My 2005 does that too... I never thought anything of it though.

 

Normal.

 

I was messing with my gauges one day and unplugged my cluster. When I plugged it back in they did what you describe. Maybe the low battery voltage is causing the gauge cluster to reset when the alternator stops supplying voltage? Just a thought.

 

No. Now you are popping ideas into everyones head. It is normal.

 

Ok, thanks!

Any idea what the battery condition indicates? Low CCA, but normal voltage? This test was done immediately after a long drive, so the alternator should of had plenty of time to charge the battery.

 

Anyone???

 

Low battery condition is pretty much when the Alt isn't running, the volts setpoint is high in the PCM, if this was lowered to ~11v the light wouldnt indicate untill that setpoint, etc..

Alternator control is PCM dependent. Normally when the truck starts the Alt is putting out ~14.4v, after a time delay and based on inferred battery temp the Alt then normally puts out ~13.2v.

Make sense?

 

Sorta...

Basically, why are my cold cranking amps low when compared to the specs of the battery? Does this indicate a dying battery, or a faulty alternator, or both?

 

Batteries wear out. What is the batt. volts with the truck off?

 

With truck off: 12.6 volts, 450 CCA's.

Battery is original, Motorcraft BXT65-650 (650 CCA's). Just over 3 years old.