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C5 Volts, what is normal?

Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
Long story short, my Dad loaned me one of his Corvettes... 1998 Pace Car, well kept but hardly anything done to it (i.e mostly original) 68k miles.

My wife drove it to work last week and it wouldn't start after work. I jumped it, and changed out the 5 year old AC Delco battery for a new Optima. I fully charged the Optima before installing.

Now I have my eye on the volts... They seem low. On the digital display, turn the key to 'On' and I'm at 11.7. seems fine, start the car, volts slowly go up over 10-ish seconds to 13.8 - 14.0. Put my foot on the brake pedal and I'll get a drop in volts to 13.5... Running to work today, lights on, wipers on, radio on, A/C on it was running about 13.5 while going. At a stop light it dropped as low as 12.8 at one point.

Is this normal? it seem low to me, I'm either over-looking at the volts or the alternator is on it's way out.
 

LLC5

Well-known member
Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
That sounds about right. The volmeter and dic display typically read .5v-.7v lower than actual battery voltage. The alternator is computer controlled, so voltage will vary depending on needed conditions.
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
Long story short, my Dad loaned me one of his Corvettes... 1998 Pace Car, well kept but hardly anything done to it (i.e mostly original) 68k miles.

My wife drove it to work last week and it wouldn't start after work. I jumped it, and changed out the 5 year old AC Delco battery for a new Optima. I fully charged the Optima before installing.

Now I have my eye on the volts... They seem low. On the digital display, turn the key to 'On' and I'm at 11.7. seems fine, start the car, volts slowly go up over 10-ish seconds to 13.8 - 14.0. Put my foot on the brake pedal and I'll get a drop in volts to 13.5... Running to work today, lights on, wipers on, radio on, A/C on it was running about 13.5 while going. At a stop light it dropped as low as 12.8 at one point.

Is this normal? it seem low to me, I'm either over-looking at the volts or the alternator is on it's way out.
Nope!! You either still have a bad battery or Corroded or High Resistance Grounds and or B+ Corroded or High Resistance Power Distribution Center Connections!!:thumb

(Or ALL of the Above!!)
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
Nope!! You either still have a bad battery or Corroded or High Resistance Grounds and or B+ Corroded or High Resistance Power Distribution Center Connections!!:thumb

(Or ALL of the Above!!)

Ok... where do I look?

When this battery was changed about 5 years ago it took out about $3500 worth of stuff. You know the drill: computer, cables, etc.
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
Ok... where do I look?

When this battery was changed about 5 years ago it took out about $3500 worth of stuff. You know the drill: computer, cables, etc.
Well I'd start personally with Testing the NEW Battery!! A New Fully charged battery should be Packing 12.7-13 Volts!! Then move on to ALL ground Locations,Including both ends of Neg bat cable and ground straps from Chassis to Engine and Harness grounds on the rear of engine!!:thumb
After that I'd move on to both ends of Pos Batt cable and the Power distribution center on the top right wheel well in front of the battery!!:thumb Remove them clean them and make sure they are absolutely clean and tight!!:thumb:thumb:thumb
C5 Grounding locations except engine are posted below!!:thumb

Gotta go to work,got a Old K5 Blazer I'm restoring waitin on me,Later!!:thumb

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