94 gmc 1500 low voltage

Asked by Jan 09, 2014 at 06:27 PM about the 1994 GMC Sierra 1500 K1500 SL 4WD Extended Cab SB

Question type: Maintenance & Repair

Starts and idles fine.  Step on brake to put in gear, get low voltage and engine dies, wipers come on also.  I repaired wiper motor circuit board before, so I disconnected the wiring harness to see if it was shorting out here.  Alternator was not charging. Put on a new alternator, charging fine around 15V.  Same symptoms, as soon as you try to move it, the voltage meter goes hard left in to the red and the engine dies.  Battery is healthy.  Where do I start looking for a short circuit that would cause such a quick drain?  Thanks in advance.  fyi I have a faulty shift solenoid...have to rev it up to 2800 rpm in first and let off to shift.  Have not looked at codes yet.

2 Answers


If you are charging 15v that is way to much. Should be 13v normal and no more than 13.8 with a completely dead battery.


You may have a short in the brake light switch or wiring to it. Or a short back at the tail light wiring to the brake lights.

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