FYI the heated seat systems in these newer vehicles are a lot more complicated than most people realize. With as much electrical crap that is on these things a high current draw item like a seat heater needs to be monitored very closely. I can see where the original posters issue may have been corrected by replacing the battery. It may not make sense to some but GM has been using load shedding strategy's in their vehicles for years. It has become more aggressive in the last few years when they started putting amp clamps on the battery cable to measure battery current draw/charging in real time. Basically look at it this way you have 150amps available from the alternator to run every electrical device on the truck. With the advent of electric power steering assist, the hotrod infotainment system, the inverter that runs the 110V outlet etc etc etc. The body control module PCM and other modules will monitor the charging status of the vehicle if the load is too great and the battery starts to discharge the various modules will go into a load shed strategy turning off low priority functions until the load can be managed. This can be aggravated by low speed driving where the alternator does not produce full output.
Does it suck that they have to "choose" like that yes. Under most circumstances the truck will operate normally but put it at -20° turn everything on with a cold alternator and battery at idle and guess what the computer is going to do as it was programmed to do and make sure the battery gets recharged first before your butt gets warmed.
The problem is we are at the end of our rope with the 12.6V battery and 14V charging systems. Manufacturers have been working toward higher voltage systems (36V / 48V charging) to give them some needed headroom to run all of the crap we have had them add to our vehicles. The problem is the infrastructure that supports the current 12V system is dug in pretty hard and resistant to change. Just think of all the companies that make small stuff like light bulbs and LED lights. If a car manufacturer pulled the plug on 12V first off they would need someone to build the new stuff and imagine the fall out from the 12v guys who were left behind.
It is coming I was in training classes on the stuff 5 years ago and they said it should be here by now. It just is moving very slowly.
i guess what I am saying is when the GM engineers say it is "working as designed" i get it....... it sucks but I get it
There is one serious problem you run into when you start introducing 36 and 48 Volt systems in vehicles: possibility of electrocution. DC voltage around 35 Volts starts to get hazardous to humans because at this voltage and higher voltages enough potential is available to break down the skin resistance and induce a potentiall lethal current flow through human body. Note that only 50 miliamps (1/20 of an Amp) is required to induce heart fibrillation in some people. This will not happen with 12 Volts or even 24 Volts because this potential is not high enough to break the skin resistance to allow any significant current flow through the body.
You cannot get electrocuted with a 12 Volt battery, no matter how large just by touching both terminals at the same time. However, 10 ordinary car batteries connected in series for the ouput voltage of 120 Volts is a lethal electrocution device that would kill a human instantly if one touched both free terminals at the same time.
Why people do not get electrocuted by touching for exmaple spark plug wire boot when the engine is running, where voltages as high as 20,000 volts are present? It will not hurt you because although the potential is high, there is not enough current available to do any damage. Similarly, static spark voltages are as high as 50,000 Volts, but the current available is negligible, so not hazard. To get electrocuted, you need both the voltage above the required treshold, and high enough curent capcity to induce the lethal curent flow (may be as low as 50 miliamps).
Edited by pm26, 08 January 2014 - 01:44 PM.