I have a 1997 Blazer 4x4 with an 4.3L auto. I've been having a serious problem with the blazer losing voltage and shutting down all lights power and motor causing me to stall. Once its stalls you can start it back up and the voltage will be at 14volts. When you start driving it began to lose voltage and stalling again. I've test with the heater off, radio off and all same results. It seems to happen more if your running a/c or heater. My gusee is that more volts are being used. I have replaced alternator, battery ground wire from motor to fire wall ignition cylinder with all new OEM parts. Still having this problem. When this dose accrue you have no power at all not even for hazard lights. Hope someone can help me out as I'm at a dead end. I've also had the battery and alternator tested 4 times. The test came back good and started too.

 

Tis the season for bad batteries to cause strange problems. Just sayin'.

 

Sounds like you have some series bad connections, most likely the ground(s) at the battery or at the end of the leads coming from the battery (not always just at the battery posts themselves). Double check those for corrosion and tightness.

 

Did you do the ground from the block to the frame? That will cause havoc on a wiring system also. I see you said you did one from the block to the firewall but the one to the frame is even more important.

 

Thanks for some good info. I have replaced the battery an alternator, had them test in the blazer and off. All test come back reading good at 14.63v, peak was 15.57v. I spent half a day yesterday checking and fixing the grounds. The ground coming from the block goes to the battery then to front brace under battery pan. Should I go ahead and add another ground from the block to the frame?. Also once I do a ECM memory test I do not experience any issues for 50 miles or more. After those miles it began to stall at random with no power to anything. It will start right back up with no problem but could do it again at any point. On the 97 the plug on the alternator I only have one small brown wire goes to this plug. Is this suppose to be the olny wire? The alternator has four metal prongs but plug has only one wire with one metal prong.