After being concerned that my regulator on the 78 Pace Car was going bad (the car was charging near the red zone on the gauge) I had my alternator rebuilt by a local shop. They did not find anything wrong with it other than the bearing, but I had them rebuild it anyway.

After starting the car cold the alternator is charging at 14.5 volts and the battery is about 14.3 (the door was open when I checked the battery) and the little brown wire running to the alternator plug in was at 14.4 as well.

These readings are with everything off (lights, heater and such). All other electrical items on the car work and the alternator reading does drop back a little when you turn stuff on, but then goes back to the 14.5 volts when its turned off. I did rev the car to 2500 rpms and the charge rates when uop to 14.8- but never higher.

Now my question- is this charging rate too high? Is it going to overpower my 12 volt battery?

Thanks!
Dan

 

14 anything is too high. It shouldn't read above 13.8. don't run it again untill it's rebuilt correctly. it needs to go back, or your batt will go boom.

 

RONG information.....the normal is 14.7 for a heavy charge on the battery just after it's been discharged or setting a while, or starting the car, depending on how much it's been flat/discharged, is the length of time that voltage stays at 14.7 ......long as it's not over 14.8, it's fine...

but when battery is fully charged, the voltage should relax to 13.3-13.8 or so, THAT is true.....

when you crank, the voltage at the battery terminals should NEVER dip below 10.5 volts....if it does, you have a bad/flat battery....

 

Thanks for chiming in now,, i guess it takes a "rong" answer to get you to share your wisdom. I stand by my answer. Charing is too high,, that's the reason for the red indicator.

 

Lets look at it this way,, while the battery may be able to "take" 14.8V, for a short period of time,,it's going to be eating charge at a great rate. If the reg is set to trip the alt on at 14.5V, the alt is going to be going full bore all the time, it IS OVER CHARGING, the electrical engieenrs at GM made the gauge correctly. Have the rebuilder set the charge point to 13.6-8 V. that way it won't kill your battery. Now THAT is correct.

 

I beleive my couple of Fluke DVM's I have had over some 50 years of messing with cars....

and the great consistency of response I get over a whole fleet of examples, running across brands and nations....

what I said is correct....

CASE CLOSED.....

 

As a battery is discharged the sulfur in the battery collects on the plates. The more sulfur on the plates; the higher the alternator charge rate will go. This chemical reaction is slowed down with weak or worn plates in the battery. Charging a battery is reversing this chemical process and puts the sulfur back into solution in the electrolyte. If you charge a very weak battery on a battery charger the voltage rate may go as high as 18 volts. If put in a car; it will go dead because the alternator will only go up to 14.8 volts (just before the red line) and not be able to reverse the sulfur back into the electrolyte. That's why they call it a "VOLTAGE REGULATOR". If the meter goes "INTO" the red zone , then your voltage regulator is no good and bad things can happen. If you put a new battery in your car you will see the voltage stay at around 13.8-14.2 volts.
For those who disagree; read up on the theory of operation of an alternator and battery life. It might save you a lot of money on unnecessary rebuilds. I don't mean to offend, just inform.

 

Bad Voltage reg. case closed.

 

BUT it can and will go to the 14.7 region upon first starting, which is what I am saying, and as the battery comes back, relaxes to 13.4 or so....

that rate/time it stays at 14+ depends on the battery, both condition and discharge ...

I think semantics is getting in the way here....

 

MRVETTE your correct. It will start at max voltage(14.8) and as the battery charges the voltage regulator drops off and all is normal. REDZR seems to have a sulfated battery. It stays at a high voltage but it's only putting out low amperage because the battery is slow to accept the charge. A 1978 car has a sealed non adjustable voltage regulator that stops at around 14.8 volts.

Time to call it a day.

 

Ok- I do not know if it helps, but I will add a few items since the battery is coming into the discussion. While the alternator was off I hooked the battery up and tested the voltage. I left the battery connected to see if there were any items draining it. The battery stayed between 12.24 and 12.27 for a 48 hour period, which led me to believe that I did not have a current drain somewhere due to a bad ground. I attributed the variance to the fact that I had the door open when testing the battery.

Would a sulfinated battery allow this?

The only think I have done to the car was to change the heater control panel (reroutes the airflow among the vents) and I went back and checked all of the connections on that and even unhooked the electrical connections to see if one of those switches were bad- but it appears not.

When I first purchased the car a few months ago, the charging needle was always a little to the right of the center mark and would dip below it with several of the accessories on. But all of the sudden its changed.

Am I worried about nothing?

Dan

 

Yes....


your car is fine.

 

Every Auto I`ve ever worked on, over the years, has a charge of 14.2-14.8v. If working correctly!!!!!!!

 

normal charge is 13.6-14.4 for all 12 volt systems.....A consistent high voltage charge can blow bulbs and damage accessories...check the acid level in the battery with an abnormal charging...you already had the alternator checked and it was found to be ok...

 

Dan I'm glad to see that you viewed everyones advice and made the correct decision. So now you've gained a bit of knowledge about the relationship between batteries & charging systems. Your charging rate will stay around 14.2 until the battery gets worn and then it will start to climb toward 14.8. Good Luck & Enjoy the Holidays.
Steve

 

I had a high charge rate problem with my previous '81. I put new alternator on no change,new battery no change. I was in rush to take trip and did not take the time to properly troubleshoot. Then my dad suggested poor ground at engine. I put a jumper cable from the engine to frame.....no more problem. So I added a new ground cable work fine ever since.14.5V or so is ok.Just my 2 cents

 

These people are still wrong. the alt has no idea what the sulfur state on the plates of the batt are, it just monitors the voltage on it's brown wire, and shuts on and off from that. 14.8 is too high, 14.4 is too high. V-reg is bad. check your other cars and see if they put out the same. they won't. that's it.

 

I believe that you are misinformed like others have said. Being in the 14 volt range when the car is first started and been sitting for a while is normal. My alternator charges at about 14.4-14.6 volts when first started and settles in the 13.6-13.8 volts range once it has been running for a while. As for the battery blowing up that observation is also wrong. My current battery with the above readings is 11 years old (that's right, 11 years, installed in 1998 (Kirkland/Costco battery, BTW) and still starts the car every time after sitting for weeks at a time. Where does some of this "advice" come from?

 

The alternator voltage regulator is going to attempt to provide what it thinks the battery needs. If it senses low battery charge [for whatever reason], it will try raising the voltage to correct that problem. As mentioned, when the battery voltage raises to a proper level, the regulator will then 'relax' and drop the voltage back. When the car is running and the battery is fully charged, battery voltage should be in the mid-13 volt range. Now, if the alternator can provide 14+ volts, the regulator may be just fine...unless it is fixed at that voltage and can no longer regulate properly.

My point here is that other problems with the electrical system [than just the battery] can cause the alternator to 'sense' a low battery condition and force it to ouput a higher voltage. In such case, the alternator would not be the problem. So, I think all responses on this thread are correct...but each response is assuming some different issue that might be wrong with the electrical system.

Proper action of the alternator is to charge at a higher voltage immediately following some significant level of battery discharge (i.e. starting the car, having headlights and/or radio on when engine not running, etc.). But, that higher charging voltage should slowly, but steadily, drop until it gets back to mid-13 voltage where it should stay while the engine is running. With engine off, an undamaged battery will almost always measure 12.0-12.4 volts...whether it can hold a charge or not. If you put a load on that battery, voltage on the bad one will 'drop like a rock', but the good one will try to stay near 12 volts and gradually drop voltage as it drains its charge.

Hopefully, the alternator change was necessary and the regulator was the primary cause for your problem. If you watch your voltmeter in the next few days and the meter responds as described above, you are 'good to go'. If the voltage level persists at a high voltage condition, you need to find WHY the alternator thinks the battery is not charged up [either because it isn't or because the proper signal is not getting back to the alternator].

 

Yes, these guys are correct. 14.5 or so is ok at start-up, but after a short whille it should taper off to 13-13.8V. Either bad regulator,possibly diode or grounding issue.