Charging problems

[eagle6]

my 1994 coupe is showing 14.5 to 15.0 on the voltmeter al the time. Is this normal or does anybody have any ideas as to what is going on or what should I check? What is the normal volt metter reading for my gauge suppose to read?

 

[Robertwav1]

My 93 reads around 14.1 or 14.2 - Calibration of the digital volt meter could be slightly off. Question is...has it always read this way? Do you have any problems electrically? Are you going through batteries often? If you are in doubt, places like sears will do a diagnostic on the charging system for about $20. Good Luck!

 

[eagle6]

I had the battery replaced a year ago at the dealership with the best one they make for that year.

 

[theadmiral94]

Our 94 shows 14.1 - 14.5, but I am replacing the alternator (all lights have a subtle flicker -- diagnosis is the rectifier in the alternator), so I'm not sure if it is correct or not, might have the new one in next week, so if it is different, I can advise.

Have you put a volt-meter on the battery to see if it matches the dash display?

What is the static voltage of the battery (after sitting for 4-6 hours)? A fully charged battery should be 12.6+, (12.4 is 75%discharged, 12.2 = 50%, etc). If the battery is not holding its charge or is being discharged overnight, and you are not driving the car alot, it might need a higher voltage while it is trying to recharge the battery.

Also, have you checked that the battery cables are tight and the that the connectors on the back of the alternator are tight? A loose wire or corroded battery cable could cause the alternator to 'sense' the wrong voltage, causing it to raise the voltage, possibly to the readings you are seeing.

 

[jpanek]

I had a very erratic volts display eventually followed by a no-start. Both cured by wire-brushing the battery terminals and cable ends.

Also, an AC ripple much greater than 0.1 VAC on top of the DC output of the alternator is a good sign of alternator failure.

 

[eagle6]

with just the the key turned on what voltage reading should I get as far as voltage I found it was a little weak starting today?

 

[theadmiral94]

The voltage displayed on the dash gauge display appears to be equal the the battery voltage (based on a quick test on our 94 just a minute or so ago).

So, the desired voltage would be 12.6 (indicating a 100% charged battery). 12.4 is 75%, 12.2 is 50%, etc.

Unfortunately, I can't tell you what would cause a weak start as ours is on jack stands and has a 2-amp charger on it, so right now it is reading 12.8 volts.

P.S. I've noticed if a car battery is drained dead two or more times, it seems to really shorten its life. Also, I've heard of 'bad' batteries, so just because yours is only a year or so old, it could still be bad. What is it's standing voltage, after being disconnected from the car for say 24 hours?

By the way, did you try cleaning the terminals (per jpanek), and checking the other end of the cable (if possible) to make sure everything is tight (including the cables connections on the back of the alternator while you have the terminals disconnected)?

 

[eagle6]

Charging Problems Maybe

I went over everything and finally replaced the starter which was drawing a little and charged the battery good last week. So far it has been charging at 14.9 at start up but has leveled off to 14.1 - 14.3 during normal driving. so far no problems keep your fingers crossed.

 

[eagle6]

Alternator is reading 15.1 vlts at startup and fluctuates between 14.8 and 14.1 while driving any ideas at all?

 

[Train_Engineer]

I have had two instances this year with my 94 with rapidly changing voltage such as described. It turned out both times that the positive battery cable was badly corroded. The second time (September), I also discovered that the positive terminal on the battery was leaking acid, contributing to the corrosion. Second battery in two years that has done that.

Suggest cleaning cables at the battery. You should get around 14.4 volts charging when clean.

Tom