Low voltage? Battery? Alternator?

[Diego0123005]

My 97 c1500 has showed some signs of starting issues. It hesitates a bit and when i start it the voltage sinks down to 9 volts on the gauge. Just today it sat about 30 minutes after my drive home from the store and it wouldnt turn over. It wasnt dead but there wasnt enough voltage to start. 1st picture is around 2k rpms and about 70mph. (For reference that the truck is moving and not idling) 2nd picture is at idle. After i jumped it started right away, voltage went up but then went back down when i removed the cables.

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[CarolinaOBS]

Go to auto zone or somewhere and have them test your battery and alternator, those would be the most likely culprits.

 

[chipskittles]

I would put a multimeter on the battery with the engine running and get the volts. Then read the volts with the engine off. If there's not much of a difference it's most likely your alternator. The summer heat kills them. Make sure you charge the battery fully before starting the vehicle with the new alternator. Alternators aren't made to charge dead batteries, they just maintain them. Does the battery light on the dash come on with the vehicle off and the key in "on" position? If not the bulb could be out and this can cause the alternator to not charge.

 

[Eskimomann209]

Truck running
Disconnect positive cable
She dies yer alt is bad

 

[chipskittles]

Truck running
Disconnect positive cable
She dies yer alt is bad

That's a good way to kill any alternator with a solid state voltage regulator, ie any alternator made in the last 30 years

 

[slowburb]

Sounds like the alternator to me, if the voltage decreased with the engine running after taking off the jumper cables. It's free to have it tested.