low voltage at idle
Le Mans Master
Joined: Sep 2014
Posts: 5,278
Likes: 539
From: Kelowna BC
"My Dad's a TV Repairman"
Joined: Jul 2014
Posts: 471
Likes: 153
From: San Diego
Might as well just go ahead with alternator, battery, belts, pulleys, plugs, wires, coils, ECU, MAF, TPS, CTS and quite possibly the engine wiring harness- Got to be thorough with those daggone electrons running around!
Oh. Experience speaking here. Replace this thing:
Last edited by Fed Up; Aug 31, 2016 at 08:05 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Pro
Joined: Jan 2016
Posts: 519
Likes: 66
From: South Salem NY
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I would add to the HOOPLA but, I am sure that the OP really does have an issue and would like to SOLVE IT.
SO,, here goes.
Please use a volt meter and read the terminals DIRECTLY on the battery when you see the LOW VOLTAGE reading.
The volt meters inside the car (digital & ANALOG) are NOT showing you the actual battery voltage.
They display the voltage on the HOT in RUN & START or HOT in ON and RUN DC buss. That buss comes from the IGNITION SWITCH output! If the ignition switch contacts are dirty/burnt, it can cause a low voltage issue for that buss.
The BATTERY recharge path comes from the large connection on the back of the alternator "BATT TERMINAL" It then goes to the STARTER SOLENOID main terminal and then it goes to the battery POSITIVE Terminal. If the starter solenoid main terminal is dirty/loose or corroded, it can effect charging voltage.
Bill
SO,, here goes.
Please use a volt meter and read the terminals DIRECTLY on the battery when you see the LOW VOLTAGE reading.
The volt meters inside the car (digital & ANALOG) are NOT showing you the actual battery voltage.
They display the voltage on the HOT in RUN & START or HOT in ON and RUN DC buss. That buss comes from the IGNITION SWITCH output! If the ignition switch contacts are dirty/burnt, it can cause a low voltage issue for that buss.
The BATTERY recharge path comes from the large connection on the back of the alternator "BATT TERMINAL" It then goes to the STARTER SOLENOID main terminal and then it goes to the battery POSITIVE Terminal. If the starter solenoid main terminal is dirty/loose or corroded, it can effect charging voltage.
Bill
Drifting
Joined: Jul 2015
Posts: 1,844
Likes: 375
From: San Jose, CA
Thread Starter
4th Gear
Joined: Aug 2016
Posts: 4
Likes: 1
From: Arrington TN
Low voltage at idle #2
2000 vette coupe 59,000 miles: My voltage meter(in the dashboard) would read as low 11.8v at idle with ac and head lights on. I used my hand heald volt meter it read 12v at idle with same loads. I had the alternator checked while on the car at o'rilleys (car was at operation temp) and they said the alternator (GM original)was bad. on 8-30-16 I bought a rebuilt (only kind they sale) altenator from Auto Zone (they had 20% off sale). This replacement AZ rebuilt altenator would read 14.1, engine cold at idle with ac, head lights on. after the engine warmed up to 180 degrees (about 9 miles of driving) the voltags (dashborad gage) would drop to 13.5 at speed 30+mph, but would drop more to 13.1 -12.8 at idle. I then had my origianl GM altenator checked, off the car at AZ, and they said the GM altenator was ok????, Now i am thinking to replace the voltage regulator in my GM original altenator and taking the AZ altenator back for a refund???
Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
If you still have your original alternator, KEEP IT! Do not give it back as core. Plenty of horror stories here, just do a search on the subject.
C5s are very "picky" with alternators and when these are not replaced with the right ones, it causes charging system fault codes.
When your car is showing low voltage, have you checked what voltage you have between the alternator and the battery's positive post? It should be zero or very, very close to it. If it is significant, you probably have a bad contact at the starter or a bad fusible link. The chain is alternator-starter-battery.
C5s are very "picky" with alternators and when these are not replaced with the right ones, it causes charging system fault codes.
When your car is showing low voltage, have you checked what voltage you have between the alternator and the battery's positive post? It should be zero or very, very close to it. If it is significant, you probably have a bad contact at the starter or a bad fusible link. The chain is alternator-starter-battery.
Last edited by GCG; Sep 4, 2016 at 11:35 PM.
