Intermittant Battery Light, BUT voltage meter says normal

[EBExp2000]

I'm still trying to diagnose my intermittant battery light issues. I told the dealer to "check the alternator's output" and they charged me about $50 to check the battery voltages and the charging voltage.

I've now hooked up a multimeter to a cigarette lighter plug. I get the intermittant battery light, but the multimeter is reading 13.9 -14 volts. This is with NO LOAD. No accessories are running, including headlights. It does it when cold, or warm.

Now, one question is: how the heck does this battery idiot light work? Does it just see voltage? I see the voltage as perfect. The dealer saw the same. Could it be a bad sensor or bad idiot light? I'm not an idiot to automotive issues. I'm quite confident in my work, and I'm very capable. This just doesn't make sense, though.

[EBExp2000]

No ideas??

[ritschner]

The battery voltage light is triggered by the PCM. My suggestions would be to check the PCM connections and ground.

[EBExp2000]

I can definately check the PCM....but I'm new to this motor. Where is it?

The PCM just reads voltage, correct?

[ritschner]

The PCM (powertrain control module) is the computer that runs the engine and other electronics on the truck. It is located between the drivers side battery and the fender. You will need to unhook the drivers side battery and remove the plastic cover. You will then see the PCM and its conections. Most of the connections under the hood tie into the PCM in some way or other and should be checked. The easy way is to unplug and replug them.

[mpc]

I had the same problem, one of the brushes in the Alt. was sticking. Cleaned the brush holder, still working fine. [img]/ubbthreads/images/graemlins/warmsmile.gif[/img]