1993 GMC Sierra will not idel and will stall

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

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

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

JDL

MECHANIC
16,098 POSTS

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