Alternator light came on 16.5 to 17 Volts. Must be a bad Regulator.Can this too high of voltage hurt anything?

 

Take a voltage reading with motor running, directly at the battery and compare readings.

 

Dude the regulators toast yikes yes you can fry the battery not to mention what other electrical gremlins that can occur later. But do a volt check first before you do anything as it could be a faulty gage reading but I sure doubt it

 

You can fry the ECM, radio, cluster, heat/ac controller, spark module, heater fan motor controller, ABS computer, and cook the battery. Either replace the voltage regulator or buy a rebuilt alternator! Don't run the car until you fix this!

 

A bad battery can also cause this. Get your charging system checked out asap.

 

This is not true! The maximum voltage you can ever see from a car lead acid battery is 13.2 volts!!! It is impossible to see 16.5 volts. The 16.5 volts comes from a defective voltage regulator in the alternator!

 

a 100% correct and true statement!

 

Anyone wanna make me a bet?

Read my post again. I said the battery may have caused this I did not say replacing the battery would correct your problem. For the noobies who think they know what they are talking about: Your battery balances out the rectified output of your alternator. If your battery is fried IT IS possible to have voltage spikes exceeding 14volts and in the process damage your voltage regulator and any of the other modules on board as well.

My source? I have seen this fact demonstrated to me at the GM training center by professor Copeman using an oscilloscope.

So tell me: Why am I 100% wrong again and what is your source?

 

All electronic components contain factory compressed smoke...when you let the smoke out there bad!

seriously though I would pop the altinator off and have it checked out,
probably a bad regulator.

 

Here is my source, ....ME. I am an electronic engineer and I understand electronics and how automobile charging systems work. Your battery doesn't do squat when the engine is running and the alternator is working as it was designed to because current only flows into the battery. The alternator is designed to put out 14.7 volts and if you look at the alternator waveform with an oscilloscope as I have, you will see a very small ripple in the alternator output and the bottom of the ripple is way above 13.2 volts (the maximum possible voltage a lead acid battery is capable of) , so all the time the battery is being charged by the alternator and NO current can flow out of the battery! The voltage regulator in the alternator adjusts the armature current to maintain 14.7 volts output no matter what the condition of the battery is. If the battery has several shorted cells, charging current could exceed the current rating of the alternator and the current limit part of the voltage regulator overrides the voltage regulator and drops the alternator output voltage so the output current doesn't exceed the alternator rating. If the battery goes open circuit, the alternator still tries to maintain 14.7 volts and the only way voltage spikes can occur is for the car electrical system to have a very high inductance component. While there are inductive components in the electrical system they don't have high inductance and the resistive load would damp any spikes due to alternator ripple across any inductive load. The OP has an alternator with a defective voltage regulator and his ECM detected this and turned on his battery symbol light on his dash to alert him that his alternator has low/no output or too high output. Professor Copeman needs some more schooling , OR, his oscilloscope needs to be repaired!

 

Oh, so you were born with this knowledge? No books or teachers?

If you did we wouldn't be having this debate. I don't care if you work for NASA, nobody is right all the time and this time you are wrong. By the way.......Didn't one of their Space Shuttles blow up on it's own? Don't they understand how to build rockets?

False. The amount of field current allowed to pass through the regulator to the rotor, or field coil, is controlled by the voltage feedback from the battery

False

Many add ons including Racetronix Fuel pumps are fed directly from the alternator output.

False

Ever heard someone smack their flywheel with their starter while the cars running? That's a series circuit. Current flowed out of the battery while it was being charged to the starter

False

The regulator has two inputs and one output. The inputs are the field current supply and the control voltage input, and the output is the field current to the rotor. The regulator uses the control voltage input to control the amount of field current input that is allow to pass through to the rotor winding. If the battery voltage drops, the regulator senses this, by means of the connection to the battery, and allows more of the field current input to reach the rotor, which increases the magnetic field strength, which ultimately increases the voltage output of the alternator.

False. Thats backwards. See my quote above. As battery output decreases, Alternator output increases. This is why every manufacturer of alternators out there ask you to NEVER unplug the battery while the cars running.

Yes we all agree his regulator is faulty, assuming its not false readings at or to the gauge. The question is why did it fail. The battery CAN effect the output of a voltage regulator. I know this in theory AND it happened to my very own Vette. Voltage was high on the gauge, lights going on and off on the DIC like a bad UFO movie...changed the battery all was good.


I agree a faulty oscilloscope may be to blame and someone does need more schooling.

.......but it's not Mr Copeman.

 

1. Sure I read books about electronics and became an amateur radio operator and built my own equipment long before I went to college and got a BSEE.
2. I'm not right all the time, but I am right about the claims I made in my previous post.
3. You are dead wrong! Field current is supplied by the alternator because the alternator is the only device supplying current to the car electrical system when the engine is running. You can easily prove this to yourself by drawing the Thevenin equivalent circuit of the battery connected to the Thevenin equivalent circuit of the remainder of the car electrical system. This circuit shows you that current flows only from the alternator into the battery!
4. Add on fuel pumps connected to the battery are also connected to the alternator output and ALL power to the car electrical circuit is supplied by the alternator. See my answer #3.
5. The engine has to run before the alternator can spin fast enough to generate 14.7 volts. The main function of the battery is to provide the energy to the starter!
6. Look at the circuit diagram for any car with an alternator or even a d.c. generator. The alternator output goes directly to the battery and the voltage regulator power comes from the ignition switch which is connected to the battery. No current comes from the battery when the engine is running, ALL of the car electical current requirements come from the alternator. Also, see my answer #3.
7. Again, you are dead wrong. When the engine is running, there is no battery output, current is flowing into the battery from the alternator. If the battery is shorted, then the alternator output will initially be determined by Ohms law, I = E/R , I = 14.7v/(battery resistance in ohms). This current can exceed the alternator rating and the alternator is protected by the current limit circuit which is part of the voltage regulator.
8. Mr. Copeman may have shown voltage spikes going higher than 14 volts on an oscilloscope, greatly depending on the battery condition. I would like to hear Mr. Copeman's explanation as I have never seen spikes of this amplitude. I am prepaired to acknowlege this possibility, but everything else I have said Mr. Copeman will also back up.

 

This is pointless so I will remind you of this. I have actually done it and proven this theory. My car's gauge showed more than 14.2volts as well and I had remembered the FACT that the battery lends a hand in the output of the alternator. I immediately changed the battery and all was good.

Anyone who knows anything about alternators on modern cars knows to NEVER disconnect the battery while the engine is running due to huge voltage spikes that can damage electronics. This is more proof that what I say is true. If the alternator could regulate the voltage properly and not exceed 14.2volts without the load of the battery then this statement would be false.

You can't have it both ways. ......or are you saying that you won't see excessive voltage with the battery disconnected?

 

There will likely be a voltage spike when you disconnect the battery with a running engine for this reason. You will have suddenly reduced the current load on the alternator, namely, the battery charging current and the voltage regulator cannot instantly correct the output voltage. So you will have a voltage spike and the regulator will quickly reduce the output voltage to 14.7 volts. Unless the battery was badly discharged and the charging current was high, the drop in current will be relatively small and the voltage spike will also be small and not dangerous. All of the circuits in your car have protection against overvoltage and voltage spikes because they are common.
It is impossible for current to flow out of the battery when the alternator is charging the battery and current is flowing into the battery! How you can know the opposite of the laws of physics is known only to you !
I have owned 10 cars in my lifetime and I have owned the factory service manual for 7 of those cars and read them all. There was no warning in any of those 7 manuals to not disconnect the battery with the engine running. By the way, when you shut your engine off, the ignition switch disconnects the battery from the rest of the cars electrical system which has the alternator still connected and turning. Explain how you aren't supposed to disconnect the battery when that is what you do everytime you turn the ignition off?
I currently have the service manual and the electrical diagnosis service manual supplement from GM for my 87 Corvette and it does not say to disconnect the battery with the engine running anywhere in either manual.

Oh yeah, if you want to see a really high voltage spike on your cars 12v system, hook up your oscilloscope across the battery and start the engine. When the starter motor kicks out, you are going to be in for the surprise of your life!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!

 

Wow you are just a fountain of misinformation aren't you. If this was true then why are PCM failures so common when giving people a boost?

That's old school thinking You would be suprised how many things we have learned since 1987. Not only have I read 50 times as many service manuals that you have, but I have spoken to the people that wrote those books and they sent their rep to teach us that a battery can cause your regulator to fail and damage many electrical components through over voltage.

The battery, alternator and starter are all one big series circuit that are always connected to each other in any position of the ignition switch. The engine shuts off and while the alternator still spins for a bit, the battery is still connected to the alternator and still is assisting in keeping the regulator alive and working properly. The battery relative to the alternator is never disconnected.



By the way, there are circuits still active with the igntion in the off position. We call those "Hot at all times"

It also doesn't say hit the alternator with a sledge hammer to free up and carbon tracking on the coil windings yet we know that's not a proper procedure.

 

http://www.bmwmotorsports.org/pdf/BM...20-%202003.pdf
Taken from page 160 of the BMW X5 Owners manual and I quote:

Do not disconnect the battery when the engine is running. If you do so, the ensuing voltage surge will damage the vehicle's onboard electronics

 

Boy did I screw up
The old school guy that I am when my son told me the voltmeter was low the first thing that I did was to start it, pull the negative cable, and see if the it died.
When it did I replaced the alternator (knowing that the regulator in integrated).

In this case it seems that i did no damage because that was the problem. I could of cooked some elctronics components if it wasn't the problem and i should know better.
I have to remember that cars today are much easier to break than when I was hot-rodding 20+ years ago.

 

I know what you mean!!! Things were much simpler before computers etc. Now the best (safer) thing is a test with a digital volt meter.

 

Partial Quote from Vette Threat
The battery, alternator and starter are all one big series circuit that are always connected to each other in any position of the ignition switch. The engine shuts off and while the alternator still spins for a bit, the battery is still connected to the alternator and still is assisting in keeping the regulator alive and working properly. The battery relative to the alternator is never disconnected.
________________________________________ ____________________

You clearly have a poor understanding of automobile electronics because the battery, alternator,and starter are NOT one big series circuit !!!!!!!!!!!!!!!!!! The battery, alternator and starter are connected in PARALLEL. You don't know what you are talking about!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!Fur thermore, when you shut the ignition switch off in a C4 , the power to the voltage regulator is turned off from one of the three contacts in the ignition switch. Again, you don't know what you are talking about!!!!!!!!!!!!!!!!!!!!!!!!!!
I have been on the Corvette Forum for 6 years almost every day and I have never read anyone posting that jumping their battery or disconnecting their battery damaged their computer. Car computers have an MOV (metal oxide varistor) on the 12v power line to protect them from voltage transients and they also have a voltage regulator that provides additional spike protection, the cluster also has a MOV for spike protection and a voltage regulator. So does the radio, in fact all sensitive electronics in your car was designed to deal with the normal voltage spikes that occur across the battery. All inductive circuits in your car, motors, spark coil, injectors, solenoids, ALL of them produce a voltage spike when they are turned off.

Go to any car dealer or independant car repair department, they all have a big battery charger cart that has a switch position to start a car with a dead battery, and guess what, the battery clips have to be connected and disconnect from the car battery. There is a voltage transient when you connect a battery too, but I doubt you know that. Even the car manufacturer has to connect the battery for the first time!!!!!

Vette Threat, you are just another poster that thinks they understand how cars work (but don't) and in this case their electronics. You don't want to read or hear about how they really work, you are right and everyone else in the world is wrong, your mind is made up !!!!!!!!!!!!!!!!!!!!!! Damn the facts and the laws of physics.
Somewhere on the internet there must be site for people like you who only partially understand anything but want to argue that they are right, why don't you find it and argue with them, you aren't appreciated here and you do not add anything to C4 tech.

 

Having been in the battery business for awhile some years ago, I have indeed seen a defective battery cause overcharging to this extent, that is wide open and unregulated charging. Not common but indeed possible. Batteries can cause some bizarre problems. Had I not witnessed it first hand a couple of times, I'd likely be in agreement with the naysayers. Trust me on this one, folks.

BTW, I didn't just sell batteries and install them. We did full, starting and charging system service including diagnosis, component replacement, wiring and whatever else was necessary to fix the problem.