Item Posts    Sort Order

My 1986 corvette just started showing 15-17 volt on the dash sometimes

 
C4SROCK
I love my Chevy Chevette!
Posts: 3
Joined: 10/09
Posted: 10/14/09 04:31 PM

My 1986 corvette just started showing 15-17 volts on the dash sometimes, only when it runs for a while it would go from 13.5 to 17 volts and then back to 13.5-13.9 in park with everything on and 12.9 under load or in drive.I checked the battery and the alternator with a multimeter and it read 14 volts all day long. The dash lights do get brighter when it hits the 15-17 and flickers a little. I checked the codes and there was a 53 high voltage that came up but the check engine light has not stayed on. could there be a issue? could this do any damage? also whould cold weather hurt the digital dash? let me know what u think. thanks  Cool  

Post Reply
waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 10/14/09 08:13 PM

with your digital volt meter... set it to 20 volts scale..   with the engine running and the head lights on..   measure between the battery negative and the engine block...

you should have less than 0.05 volts...

between the negative battery post and a chassis ground... less than 0.02 volts is what you should see...

this test takes about 2 minutes to do.. and will tell you if you have bad ground wires or dirty terminals... this is a voltage drop test..   it can only be done with current running through the wires..

if there is a difference in ground..   you will see a voltage on the meter..  

you might also want to make sure that your battery cables are totally clean..

when the grounds get intermittent .. things can blow up...

measure the voltage at the battery its self.. see if you can monitor any spikes ...

if the terminals get dirty  come loose...  the alternator has no plate for the current to go .. and the voltage builds up...

it is also possible that the alternator or voltage regulator is on its way out..  

Post Reply
Air_John
V-6 Camaros rule!
Posts: 26
Joined: 08/09
Posted: 03/27/10 12:36 PM

Had the same problem on a 1993 Corvette. We found that the wire from the alternator to the battery had burned through near the fuseable link behind the battery. The link did not blow and there was only a few strands of wire still in tact. Testing the wire with an ohm meter showed the wire to be good between the alternator and battery but the wire was not able to handle any amps so then the alternator kept rising the voltage up. We repaired the wire and everything worked properly.  Laugh  

Post Reply
brileyman
I love my Chevy Chevette!
Posts: 1
Joined: 07/11
Posted: 07/14/11 12:59 PM

My 1986 Corvette with the digital dash has the same issue. I read 15 - 17 volts upon start up, and will then black out the dash lights when it hits 17 volts  for 5 minutes and then come back on and show 13.7 volts and stay like that until I turn the car off, then it begins all over again.  I changed the Alternator with Voltage Reg and that didn't fix it. I cleaned the battery cables and then checked the voltage between the neg battery cable and chassis ground and got .01 volts (Normal). The check engine light does not turn on.

Did you ever find the problem with your car?  

Post Reply
waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 07/14/11 04:25 PM

you can test your car your self if you have a digital volt meter...    digital volt meters start at 8 bucks and you generally never need to spend more than about 20 bucks for one...


you will want to print this....  its easy to do.. takes about 5 minutes or less to run the test...

open hood...   turn digital volt meter to 20 volts DC setting..

engine off .. turn on headlights for ONE minute then turn them off

test between the positive battery post and the negative battery post....

12.65 is a fully charged battery
12.45 is a 3/4 charged battery
12.25 is a half charged battery

post what you get...   you really should do the tests with a battery above 12.4 volts after you remove the surface charge..


now... start the engine and turn the headlights on....

1.  test between the positive battery post and the negative battery post...   14.1 to 14.7 volts is expected..

2.  test between the Negative battery post and the engine block...   0.04 volts is expected..

3.. test between the negative battery post and the body of the car..  0.02 volts is expected..

4. test between the engine block and the firewall of the car...     0.02 volts is expected

depending on the digital volt meter.. you might have to change the setting to 2 volts DC for tests 2, 3, 4...

please post what results you get...    

why such small voltage expected on the 2, 3, 4 tests...  

the ground side of the electrical system needs to be fully connected ...  electrons flow from negative to positive...

if you have a dirty connection.. a loose connection..   when the circuit has a load on it .. (engine running, headlights on)  if there is a restriction/resistance between the various parts of the car..   you will be able to measure the slight difference as 0.02 or 0.04 volts DC...   if you get more than that..  and i have run across cars that have 8.5 volts on test #4..  you will easily be able to isolate the problem..

there are a few more tests that i normally run...   like from the output terminal on the back or side of the alternator to the positive battery post...  this might have 0.25 to 0.50...  thats a quarter volt to half a volt..  why so much on that circuit..  there is a lot of current flowing through that wire... more than almost any other in the car...  

Post Reply
waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 07/14/11 04:36 PM

i am also expecting to find that your alternator back looks like this..



the lower right corner is the wiring diagram for the charging system

0900C1528008fda1

you will want to figure out where fusible link B and C is...  and clean those ring terminals with a stainless steel wire brush from the hardware or paint store..   wooden handle versions have stiffer bristles usually...

there could be corrosion problems where the fusible links are bolted...  

Post Reply
clberger
I love my Chevy Chevette!
Posts: 1
Joined: 09/13
Posted: 09/07/13 01:01 PM

Hi there, I'm having the exact problem on my 1986.  Did you ever find the fix?
Thanks, Craig  

Post Reply
waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/07/13 02:01 PM

Icon Quoteclberger:
Hi there, I'm having the exact problem on my 1986.  Did you ever find the fix?
Thanks, Craig


they never came back.. but i gave them proper diagnostics to find the issue..

follow the voltage drop test above...

its simple..

then measure alternator output terminal to the battery positive terminal and post that number also..

there are a bunch of connections that will need to be cleaned...

and you could still have a bad alternator.. but this test really works...


this is a JPG image so it should be easily printed..

this is the first set of tests that have to be verified before going on as if there is a problem here. you could waste a LOT of time chasing other issues and still come back to these...

~~~~~~~~~~~~~~~~~~

VOLTAGE Drop Testing


~~~~~~~~~~~~~~~~~~~~~~~  

Post Reply
waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/07/13 02:06 PM

add test 5...  engine running.. headlight on..

positive battery post to the alternator output terminal..

0.07 volts DC max..


you will also want to check from this terminal block behind the battery tray to the positive battery terminal. less than 0.1 volts..

and from the alternator output stud to this terminal stud.. less than 0.1 volts


88 C4 Terminalblockbehindbattery Zpsc49dc171



please post results by number and i can decipher them..


craig... if you have problems.. do come back and ask.. i do drop thru these forums several times a day to check for active posts...


89 C4 L98engineharness Zpsdd58462a  

Post Reply
TO TOP