Car has very high voltage

I bought my 1994 Chevrolet Corsica brand new and it has no modifications. The car is well taken care of, has a 6 cylinder engine with 155,000 miles, is in excellent condition and has never given me any problems until now.

For the past few months the vehicle's electrical system intermittently surges from 12 volts to 19 volts (according to my voltmeter) at random times. When it surges up, a red light on the instrument panel that is shaped like a battery comes on. When it drops back down to 12 volts the light goes out.

When it surges up, my headlights get very bright and my heater blower speeds up. I have replaced 4 headlight bulbs in as many months but nothing else has blown out.

Sometimes the power surges up and down every few seconds, while at other times I can drive for hours without it surging at all. I have never smelled anything burning, nor have any of the fuses been warm to the touch when I touched them.

It does surge more often at high RPM than low. However, it sometimes doesn't seem to be affected by RPM. Sometimes it is fine until I accelerate at which time it surges, while at other times it doesn't surge at all when I accelerate.

I cannot find a pattern to this in regards to hitting bumps in the road, temperature and humidity, etc. The only item of auxiliary equipment in the car is a police scanner and I have verified that it is properly connected to the vehicle's electrical system. None of these seem to be the cause.

Due to the fact that I am worried that the car will become damaged, I have installed a brand new battery, alternator (that contains an internal voltage regulator), and battery cables. I have made a visual inspection of the many wires and cables under the hood and they all appear to be sound and in good condition.

Will someone in this newsgroup please give me some advice on what to look for? Thank you for the assistance.

Reply to
J
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I bought my 1994 Chevrolet Corsica brand new and it has no modifications. The car is well taken care of, has a 6 cylinder engine with 155,000 miles, is in excellent condition and has never given me any problems until now.

For the past few months the vehicle's electrical system intermittently surges from 12 volts to 19 volts (according to my voltmeter) at random times. When it surges up, a red light on the instrument panel that is shaped like a battery comes on. When it drops back down to 12 volts the light goes out.

When it surges up, my headlights get very bright and my heater blower speeds up. I have replaced 4 headlight bulbs in as many months but nothing else has blown out.

Sometimes the power surges up and down every few seconds, while at other times I can drive for hours without it surging at all. I have never smelled anything burning, nor have any of the fuses been warm to the touch when I touched them.

It does surge more often at high RPM than low. However, it sometimes doesn't seem to be affected by RPM. Sometimes it is fine until I accelerate at which time it surges, while at other times it doesn't surge at all when I accelerate.

I cannot find a pattern to this in regards to hitting bumps in the road, temperature and humidity, etc. The only item of auxiliary equipment in the car is a police scanner and I have verified that it is properly connected to the vehicle's electrical system. None of these seem to be the cause.

Due to the fact that I am worried that the car will become damaged, I have installed a brand new battery, alternator (that contains an internal voltage regulator), and battery cables. I have made a visual inspection of the many wires and cables under the hood and they all appear to be sound and in good condition.

Will someone in this newsgroup please give me some advice on what to look for? Thank you for the assistance.

Reply to
J

Check the ground strap from the engine to the chassis and the ground connection for the battery. Check the wiring connection on the alternator for any loose/corroded areas.

Reply to
Steve W.

The problem is with the voltage regulator. If you have changed the alternator and (internal) regulator, start looking for bad ground connections on the alternator or engine block. If the regulator does not have a good ground reference it will not work right.

--scott

Reply to
Scott Dorsey

You have a bad voltage regulator.

This is very very *very* basic stuff. You should have brought the car in for service as you're too clueless to be doing any repair yourself.

Reply to
AZ Nomad

If you have already replaced the battery and internally regulated alternator, then you need to look for a bad or corroded connection. It is a must that all power and ground connections be clean and tight. You should not wait to take care of this as an overvoltage can take out your electronics like the PCM in short order and, can cost you a lot of money. If you are not familiar with how to chase electrical circuits for faults, you should seek the services of a professional or a knowledgeable friend or relative.

Lugnut

Reply to
lugnut

A corroded connection can only lower the voltage.

If the alternator's output is restricted to 14.4V, no method of poorly connecting the alternator can result in a car's electrical system going over

14.4V.

I suppose if you disconnected the alternator's ground and connected it to the battery's positive post then you could get over 14.4V but I seriously doubt this is occuring.

Reply to
AZ Nomad

By any chance does your Corsica have an electric windshield heater? I once worked on this wierd system where the alternater would be switched over to the windshield and cranked up to as much as 70 volts. That may have just been a Ford thing, though. Late 80's or early 90's I think.

Otherwise I concur with others about checking all connections in your battery and charging circuit, especially ground straps.

Excessive output voltage is generally caused by a bad voltage regulator, or specifically the alternator's field terminal shorted to the battery positive circuit. I'm not sure if your alternator has an external field terminal.

You might check inside the alternator connector(s) or the wiring harness for visible shorts, stray wire strands, broken insulation, etc.

--Dave

J wrote:

Reply to
Dave Allured

And you have already replaced the alternator? If so it must be a problem with the field wire(s) which would be the smaller wires coming off the alternator.

You should not be driving the car in this condition. 19V will cook the electronics and if it gets the computer that pretty much means a one way trip to the junk yard for a car of that age.

Steve B.

Reply to
Steve B.

The OP said he had already replaced the alternator, which has an internal regulator and it still has the problem.

Reply to
Ashton Crusher

I find that really hard to believe -- two defective alternators.

He probably paid somebody to do it and they reinstalled the original alternator after it worked ok for a few minutes.

Reply to
AZ Nomad

Feel free to correct me if I'm wrong about this, but isn't it possible that a bad connection is causing the *regulator* to be seeing low voltage and that it is allowing the alternator to deliver higher voltages until it reads what it thinks is the proper voltage?

Pete

Reply to
ratatouillerat

I posted bad advice, sorry. This part may be wrong:

"Excessive output voltage is ... caused by ... specifically the alternator's field terminal shorted to the battery positive circuit".

No, it depends on the alternator. In some the field current is regulated by adjusting the field terminal current to positive, in others it's to ground. In some it's more complicated than either.

In any case it is possible that some kind of external short to any of the external alternator terminals *might* increase the field current and cause excessive output voltage. That is something that you *might* find by inspection if you are lucky.

It is also possible that you got a second defective voltage regulator in the replacement alternator, though that seems unlikely as Nomad pointed out.

It is possible to test the alternator with only the positive and ground connected to the car, but you must know exactly how to rig the other terminals for this to be safe, and this depends on the circuit.

At this point I think you should either find a complete diagram for your specific alternator circuit, carefully measure all terminals and understand the results, or else get experienced assistance.

--Dave

Dave Allured wrote:

Reply to
Dave Allured

Only a bad connnection internal to the alternator can do that.

If the alternator's ground isn't connected then it won't charge.

Reply to
AZ Nomad

One thing I didn't mention is that a few months ago my power steering line sprang a leak and heavily sprayed part of the engine compartment with fluid. Now that that has occurred to me, I wonder if some power steering fluid may have leeched into an electrical connector and is affecting the voltage regulator/alternator.The power steering leak was in the area between the engine and the firewall and there was very little in that area that did not get sprayed with fluid.

There is a harness coming out of the alternator that I believe has 4 wires. When I unplug it, the alternator stops supplying electrical current to the vehicle.

Thank you to all who have responded.

modifications.

Reply to
J

Not likely.

And please quit top posting and learn to trim what you quote.

?backwards everything reading like people think you do Or

Reply to
AZ Nomad

J wrote: (1994 Chevrolet Corsica 6 Cyl 155k)

For the past few months the electrical system intermittently surges from 12V to 19V (according to my voltmeter) at random times. When it surges, a red light on the instrument panel that is shaped like a battery comes on. When it drops back down to 12V the light goes out. During a surge the headlights get very bright and the heater blower speeds up. I have replaced 4 headlight bulbs in 4 months but nothing else has blown out.

Sometimes it surges up and down every few seconds, other times I can drive for hours without it surging at all. I have never smelled anything burning, nor have any fuses been warm to the touch. It does surge more often at high RPM than low. However, it sometimes doesn't seem to be affected by RPM. Sometimes it is fine until I accelerate at which time it surges, while at other times it doesn't surge at all when I accelerate.

I can not find any pattern to this such as to hitting bumps in the road, changing temperature and humidity, etc. I am worried that the car will become damaged, so I have installed a new battery, a new alternator (that contains an internal voltage regulator), and new battery cables. All of the wires and cables under the hood that are visible appear to be sound and in good condition. Can someone please suggest what to look for? __________________________________________________________________

You didn't say whether the new battery/alternator/cables made any difference, so the problem must have remained. If so, I would suspect:

Defective Control Module. Some alternators are controlled by a remote voltage regulator in an electronic module. Your post stressed that the new alternator has an internal regulator, suggesting that the old alternator did not. If so, consider replacing the defective module and installing an original equipment alternator in the car. First, try taking the module connector on and off a few times, to improve the connection.

Defective Voltage Regulator. This will cause surging, but you replaced the alternator with a new one which presumably has a good regulator. If the old alternator had a remote regulator, that regulator should be wired out of the circuit. Take the new alternator back to the parts store and have it tested.

Defective Ground Connection. A correctly regulated alternator has a peak output of about 14.5V, relative to its own ground. A bad ground connection between the regulator and the battery will cause a voltage drop to appear across the bad connection, and the regulator will add 14.5V to the spurious voltage drop. Recheck all ground connections, especially battery to block and block to chassis. Connect a wire from the alternator housing directly to the battery negative post. If this good ground solves the problem, it will confirm that there is a bad ground connection somewhere.

Good luck.

Rodan.

Reply to
Rodan

Have you actually tested at this connector to see if the proper voltages are there when they should be?

One of the wires in that connector is a voltage sensing circuit, if that circuit is open, the alternator will output too high of voltage.

Some CS series alternators have internal voltage sensing, according to the wiring diagrams, your Corsica has the external sensing circuit, protected by 2 fuse links between the alternator and battery positive. I bet one of those fuse links is open.

Reply to
aarcuda69062

There is no way the car is designed to blow out it's electrical system because of an open fuseable link.

Reply to
AZ Nomad

"Designed to blow out its electrical?"

Cars aren't "designed" to go in the ditch when a tie rod end breaks, yet they do.

Have you looked at the charging system wiring diagram for this car?

It's obvious where he should be looking.

Reply to
aarcuda69062

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