1993 Corvette high voltage
Thread Starter
5th Gear
Joined: Dec 2012
Posts: 5
Likes: 0
1993 Corvette high voltage
My 1993 Corvette C4 is having a problem where the voltage is running high. Battery light is either blinking or solid on, and voltage meter is usually between 15 and 18 volts. Check engine and Check Guages lights also turn on with this issue. The problem started yesterday.
I replaced the alternator today and there was no change at all to the problem. Any idea what else could be causing this other than the alternator?
I got the water pump changed last week, and the car likely overheated when that failed, if that helps.
I replaced the alternator today and there was no change at all to the problem. Any idea what else could be causing this other than the alternator?
I got the water pump changed last week, and the car likely overheated when that failed, if that helps.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
Here are some things you should verify.
With the engine off is the Battery voltage normal?
At the alternator case there is the large Red Battery
cable. There is also a small Red wire on the plug
that plugs into the alternator regulator. Verify the
plug connection for the Red wire is good at the regulator.
Both of these Red wires are fusible links A and B and go
to the #1 Fuse Block shown in the diagram.
Make sure the wires show no signs of burn marks or melting and are making a good connection.. They are bolted together at the fuse block with another Red cable which goes to the Battery.
For the Check Gauges light I've included a page from
the service manual that indicates what can cause that
light to come on.
If the Service Engine Soon Light came on when the engine
was running, you need to pull the code by using a paper
clip or piece of wire and short pin A to Pin G.
Turn the ignition On and the codes will be displayed
in the Dash Cluster Digital LCD.
Module 1 is CCM
Module 4 is ECM
Module 9 is ABS/ASR
Diag connector located above drivers right knee pin out
looks like below.
[F|E|D|C|B|A]
[G|H|J|K|L|M]
With the engine off is the Battery voltage normal?
At the alternator case there is the large Red Battery
cable. There is also a small Red wire on the plug
that plugs into the alternator regulator. Verify the
plug connection for the Red wire is good at the regulator.
Both of these Red wires are fusible links A and B and go
to the #1 Fuse Block shown in the diagram.
Make sure the wires show no signs of burn marks or melting and are making a good connection.. They are bolted together at the fuse block with another Red cable which goes to the Battery.
For the Check Gauges light I've included a page from
the service manual that indicates what can cause that
light to come on.
If the Service Engine Soon Light came on when the engine
was running, you need to pull the code by using a paper
clip or piece of wire and short pin A to Pin G.
Turn the ignition On and the codes will be displayed
in the Dash Cluster Digital LCD.
Module 1 is CCM
Module 4 is ECM
Module 9 is ABS/ASR
Diag connector located above drivers right knee pin out
looks like below.
[F|E|D|C|B|A]
[G|H|J|K|L|M]
Last edited by Hooked on Vettes; Dec 3, 2012 at 01:19 AM.
Thread Starter
5th Gear
Joined: Dec 2012
Posts: 5
Likes: 0
Thanks Hooked, I'll give that all a try.
With the engine off the voltage indicator appears normal, at a little under the middle (like 11 or so volts I believe)
With the engine off the voltage indicator appears normal, at a little under the middle (like 11 or so volts I believe)
Last edited by stix213; Dec 3, 2012 at 01:36 AM.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
Many of the ground wires are bolted to a driver side
engine to transmission bell housing bolt.
Look at the negative terminal of your battery. It splits
into two Black wires. Follow the two wires. One wire goes
to the chassis/frame and one Black wire goes to the engine block.
The Alternator ground is the Alternator case which is bolted
to the Alternator Bracket which is bolted to the engine block.
If you have a ohm meter verify you have zero resistance
from the Alternator case to the negative terminal of the
battery.
Did the Alternator problem occur after the water pump
was installed?
The Alternator regulator compares the voltage
of the Large red wire with the Small red wire. The regulator
then determines what voltage the Alternator should output
to keep the battery charged. If something is wrong with the
Small red wire such as a bad connection it could cause
your problem.
You can also damage a replacement Alternator if you run
it long enough at maximum output if the original problem
wasn't fixed.
Most auto part stores will check the Alternator for free.
engine to transmission bell housing bolt.
Look at the negative terminal of your battery. It splits
into two Black wires. Follow the two wires. One wire goes
to the chassis/frame and one Black wire goes to the engine block.
The Alternator ground is the Alternator case which is bolted
to the Alternator Bracket which is bolted to the engine block.
If you have a ohm meter verify you have zero resistance
from the Alternator case to the negative terminal of the
battery.
Did the Alternator problem occur after the water pump
was installed?
The Alternator regulator compares the voltage
of the Large red wire with the Small red wire. The regulator
then determines what voltage the Alternator should output
to keep the battery charged. If something is wrong with the
Small red wire such as a bad connection it could cause
your problem.
You can also damage a replacement Alternator if you run
it long enough at maximum output if the original problem
wasn't fixed.
Most auto part stores will check the Alternator for free.
Last edited by Hooked on Vettes; Dec 3, 2012 at 09:18 AM.
Thread Starter
5th Gear
Joined: Dec 2012
Posts: 5
Likes: 0
Yes the problem did start to occur after the water pump was replaced, but not immediately. I had a local shop replace the pump, and I drove it home without this problem. The car sat for a week on the street (I have a long commute so usually drive a commuter car on week days), then I started it up and that's when all the warning lights + high voltage on the gauge started. So I can't say that the shop did something that caused it because it was fine on the drive home.
I'll do the ohm meter test when I get home. Thanks again.
I'll do the ohm meter test when I get home. Thanks again.
Drifting
Joined: Sep 2003
Posts: 1,363
Likes: 7
From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
check the battery
If the battery doesn't 'push back' voltage against the alternator's output, it could cause the alternator to run too high a voltage.
11 volts suggests a bad battery/dead cell.
A battery that has 'rested' for a few hours, should show following voltages:
12.66 = fully charged
12.4 = 75%
12.2 = 50%
12.0 = 25%
Less than above suggests a bad battery...
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Thread Starter
5th Gear
Joined: Dec 2012
Posts: 5
Likes: 0
Hey thanks a bunch to anyone who posted. The two wires that are going from the alternator to behind the battery are corroded to hell right near the end, and the one that appears to be going to the voltage regulator has a break since when I disconnect it the end just flops around held only by the insulation. Looks like the regulator couldn't read the current charge system voltage so was just maxing out the alternator output or something I guess. So about $1 or so in wire and I think I'm back in business. 
I'll keep an eye on that battery after I fix this wiring and if it doesn't liven back up I'll look at replacing it.
I'll keep an eye on that battery after I fix this wiring and if it doesn't liven back up I'll look at replacing it.