1993 GMC Sierra will not idel and will stall

Tiny
CAPER33
  • MEMBER
  • 1993 GMC SIERRA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Hi there, The truck will idel ok at first and then stall. Expeially if you turn the radio, wipers lights or heater on or put the break on. If I have the truck unstarted and turn the lights on, they are very very dim.I had the altenator checked and its perfect. If I was driving it, I will have to floor the truck so it wont stall and then come to a stop sign, it will stall again, Can you please tell me what the problem would be
Wednesday, November 11th, 2009 AT 1:36 PM

3 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Welcome to the forum. I'd have to make sure the battery has a full charge and the connections are good. Was the alternator tested on or off the vehicle? If the alternator was tested off the vehicle, it is possible the alternator may be ok, maybe problem with wiring circuit to or from the alternator?
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Wednesday, November 11th, 2009 AT 1:49 PM
Tiny
CAPER33
  • MEMBER
  • 2 POSTS
Hi there, its a brand new batter with a full charge to it, yes the alternator was tested off the truck
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Wednesday, November 11th, 2009 AT 1:58 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS


https://www.2carpros.com/forum/automotive_pictures/170934_gmc_alternator_1.jpg



The above is wiring circuit for alternator. If you turn on headlites with engine off, that is battery voltage. Use a digital multimeter across battery posts, everything turned off. 12.6 volts is considered a full charge. Start the vehicle, take second reading across battery posts, the second reading should be higher than the first, if it isn't, the alternator isn't charging for some reason. you can also take a reading at alternator bat terminal, same deal.
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Wednesday, November 11th, 2009 AT 2:34 PM

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