Welcome to the Corvette Forums at the Corvette Action Center!

Charging question

VetVette

Member
Joined
May 19, 2017
Messages
10
Location
SW Ohio
Corvette
1985 Coupe Dark Bronze Metallic
So a couple weeks ago I bought an 85 with 23,000 miles. Tonight I had the voltage meter on instead of coolant temp. Long story short is that while idling in park, the voltage is fine. But if I'm stopped at a traffic light, I can watch the voltage get lower and lower. Car seems to idle around 600 in park and around 560-570 without the A/C on.

Am I looking at possibly needing a new alternator? Can I adjust the idle a little higher? What are your thoughts? Thanks.
 

LLC5

Well-known member
Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
So a couple weeks ago I bought an 85 with 23,000 miles. Tonight I had the voltage meter on instead of coolant temp. Long story short is that while idling in park, the voltage is fine. But if I'm stopped at a traffic light, I can watch the voltage get lower and lower. Car seems to idle around 600 in park and around 560-570 without the A/C on.

Am I looking at possibly needing a new alternator? Can I adjust the idle a little higher? What are your thoughts? Thanks.




Make sure that the battery cables are clean and tight ,and have your battery properly load tested with a carbon pile tester, not a theoretical electrical tester, if the battery is bad or on it's way out the voltage can be low. But basically you need to perform the voltage test at the battery clamps with a quality voltmeter, gauges are not always accurate.
 

Hot Rod Roy

Well-known member
Joined
Jul 6, 2005
Messages
317
Location
Mission Viejo CA
Corvette
Yellow '84 Coupe
Long story short is that while idling in park, the voltage is fine. But if I'm stopped at a traffic light, I can watch the voltage get lower and lower.

This may be normal as the battery recovers its charge after starting the engine. You say "voltage is fine". What voltage are you seeing? Check the voltage at the battery terminals with an accurate volt meter while the engine is running. Do you see the same voltage decrease? Do you see a different voltage if you test the output of the alternator (alternator red wire to battery neg. post.)? Do you have any extra accessories in the car (i.e. super stereo)?

:w
 

DonB

Well-known member
Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
Make sure the ground cable is making a good connection where it meets the block, too. Also, I Can't remember off hand right now(if the '85 has this), but check for the ground junction at the left, lower, rear of the engine by the trans. and make sure the connections are clean & tight. It may have NO effect on your issue, but it'll cause a ton of freaky things if NOT cared for.

Checking at the battery(or the hot pole on) the alternator it should put out about 13.5 volts when running. If the battery is down or bad the alt. can put out up to around 15VDC.
 
Last edited:

VetVette

Member
Joined
May 19, 2017
Messages
10
Location
SW Ohio
Corvette
1985 Coupe Dark Bronze Metallic
Thanks guys. I meant to check it out some this weekend, but the weather was so nice I had the top off and was cruisin'. Plus I cleaned out the lean to next to the garage to park it under.


Sent from my iPhone using Tapatalk
 

Vettehead Mikey

Well-known member
Joined
Aug 26, 2003
Messages
3,486
Location
Not that far from Ottawa
Corvette
1973 Coupe
So a couple weeks ago I bought an 85 with 23,000 miles. Tonight I had the voltage meter on instead of coolant temp. Long story short is that while idling in park, the voltage is fine. But if I'm stopped at a traffic light, I can watch the voltage get lower and lower. Car seems to idle around 600 in park and around 560-570 without the A/C on.

If you didn't look at the gauge, what other symptoms are there?
 

Bagoftrix

Well-known member
Joined
Jun 19, 2016
Messages
90
Location
Morgan, Utah
Corvette
1990 Bright red coupe
I had the same problem with my 1990. Replaced my alternator and everything works great.
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Top Bottom