Ron U.S.M.C.

The car needed a jump the other day .
Nothing but a fast click,click,click.
It started within second when jumping it and
all the battery needed was a little topping off with a charger.


I took it down to my local auto parts store and had them hook up there testing device and the battery even though it had a full charge was listed as bad. The alternator tested fine.



The car seems to start ok but the little volt gage with the battery on it used to read just above the 13 on the middle line and now it reads below it.
I’m going to replace the battery but why is the gage off ?

gt4373

How Old Is The Battery.

LiquidBlue

In the old days, that gauge indicated alternator charge value, if I recall correctly, you could have a dead battery, and the gauge would still read good. But if you had a good battery, and a bad alternator, the gauge would be off. Is it possible you're alternator test needs redone? Also in the old days, there used to be a separate regulator that regulated the alternator charge to the battery. You would need to test both. Is the regulator built into the alternator on these cars?

I did a quick Google (1990 Firebird Voltage Regulator was the term I searched) and found several threads on this subject here at TGO. Some good ideas here, which include making sure belts are tight, cables connections are clean, and the quick auto store tests sometimes not that accurate. Also, what occurs when you put your car under load, stereo on blasting, lights on, a/c on, does voltage drop a bunch? More signs of something wrong with your charging system.

naf

iTrader: (7)

Batteries are tested by a load tester. The battery can read 12 volts, but still not have enough power to provide that voltage under load.

The gage reads system voltage. With the engine off it will read battery voltage, which should be around 12-12.5 V. With the engine running and the alternator charging it should read 13-13.5 V. Our alternators will need to see some rpm's before they actually start charging, usually around 1300ish. So a fresh start that hasn't exceeded that rpm level will still show battery voltage at the gage.

A standard test of the alternator is to read battery voltage with a meter, engine off. Then read battery voltage with engine on, alternator charging. Should see the above voltage readings. Too high or too low with alternator charging is bad. This is more a definitive 'bad' test for the alternator though, as it can fail and still provide good voltage readings.

Best to have the alternator checked. A failing/weak alternator could cause battery failure.

If you haven't replaced the battery yet, check your gage readings afterwards. Should be back to what is normal for your car.

Ron U.S.M.C.

Thank guys.


Battery is old = 6 years


The only way to get to the red wire on the alternator is to pierce the wire with the tip of the multi tester. The rubber boot covering the actual terminal is hard and the rear of it is against the front side of the valve cover.


I'm not going to mess with it.


Instead I used the battery terminals.


With the car off the battery read 12.42 v (with a full charge) and again with the car running in open loop. (idling pretty fast) and it tested 14.63 v.


The gage in the car is now reading above the 13v line where it usually is.


I'm going to run the car like it is for a while (I spent all my money or Christmas presents).
until I get paid again.




Thank again guys.....

naf

iTrader: (7)

reading charging voltage at the battery is perfectly fine.

Sounds like everything is good, but keep an eye on it. 14.6 might be a smidge high.

xmas=fun

Beeman

Why is the gauge off??? First of all the vehicle is old, sorry it's the truth. the wiring in the car is old too. The gauge has been working and is tired. The ground connections for the instrument cluster might have a poor connection. To prove anything you have to back probe the wires feeding the gauge.

sofakingdom

iTrader: (1)

Most likely there's a bad connection somewhere; batt cable end most likely. Check both ends of both cables and also the end of the charging wire at the big red post on the alt. (No excuses about the boot... just do it)

cardo0

Here in the Nevada desert 4 years is normal for lead acid battery life. I have at least 2 of these batt testers and love'm: http://www.harborfreight.com/100-amp...ter-61747.html. I can load test the batt, measure its voltage and check the alt charge voltage all in less than a minute.

If your in dash gauge is responding then close is good enough - never knew a stock voltage gauge that was accurate. Not worth the effort to replace usually unless u have the dash out for something else.

Just connect that batt tester and measure the voltage. The flip the test switch and see what it reads for batt capacity - it even has colors for good or weak. Then start the engine and see how the alt is charging - should have 13-14volts. Thats it. U now know what batt voltage is and what it can do. U know the alt output volts to and it cant charge a 13.2volt lead acid batt with less than 13.2 volts.

Hope this helps.

Ron U.S.M.C.

The battery in the car now that I tested with a multi tester would not start the car again today. Cranked a little and then click,click,click.
I just put a new battery in tonight and it started right up. I will see how it acts tomorrow.


I have a Harbor Freight down the street so that tool is on my list.




I lived in Laughlin NV working as a Bartender for a lot of years. I drove a 1970 Chevy Blazer with the top off almost year round.
The places I took that truck in the desert were both breathtakingly beautiful and terrifying at the same time.
I miss it a lot

cardo0

Yea a multi meter does not "load test" the batt. U need a load tester for that and u could probably borrow from the local parts store that has a tool loaner policy. Or they might just do that at the store if u bring them the batt.

Kinda funny as i miss the So Cal beaches and ocean. Its mostly hot or cold here. This fall lasted like a week before it got cold.

Take care Ron and hope this helps.

Ron U.S.M.C.

Well I put this battery in the car and maybe its my imagination but it actually feels like its running stronger. The gage is just above the middle 13v mark and it starts nice a strong.


= http://www.walmart.com/ip/Everstart-...ttery/16782711


I'm not sure but I think I might be getting that tool mentioned above for Christmas.


Thanks guys

NINÅ