Chevy Suburban Electrical Power Management

2010 Chevy Suburban 1500 4wd. Had system Checked at dealer. Started truck and let run to warm up, as I walked out to drive I smelled an electrical burning smell. I got in the truck and checked the basics and all seemed fine. As I was driving the Volt gauge was showing under 14 volts. As I drove it dropped even lower almost to what I figure was not much more than 12v.

When I shut off the truck I waited short time and then re-started voltage back up to over 14v. I figured that it was the battery just recovering. Drove my Chevy again and the voltage dropped as before. Sent to service at dealership then checked and stated that the charging system was working as designed. Does that sound right to you?

Question:
Does the system operate as he told me? Why would it allow the voltage to drop down to almost 12v while running? Took vehicle to my son's repair shop and tested voltage it was at 12.9 when I first got there and then went to 13.7 before dropping back to 12.5 a short time later.Tech told me that the computer shuts the charging down when the vehicle doesn't need it. Sounds like a story to me, and why the electrical burning smell, something def cooked under the hood.

Answer:
Yes, the GM Tech was correct. This charging system is called "Electrical Power Management (EPM)". Basically a sensor on the positive battery cable senses battery voltage / amperage and electrical load while the truck is running. Then the Body Control Module(BCM) determines how much alternator charging capacity is needed. The BCM tells the Powertrain Computer (PCM) how much charging is needed, then the PCM controls the voltage regulator as a pulsed width signal for a controlled output.

For example, when there is a heavy electrical load such as the rear defroster, blower on high speed, headlights on, engine at idle- the PCM will boost the charging voltage. This system is designed to extend battery and alternator life.

Now, the burning smell does not seem related. If the truck is absolutely new with very low miles, then some smells are normal. If something has melted, I would assume the Tech would have spotted that quite quickly. Maybe there is just some plastic melted on the exhaust. Burned wires under the hood would have been easily seen and repaired.


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