Alternator or Battery???

[-=Jeff=-]

how do you know which it is?

I know my battery is about 5 years old and is an Optima red top, I always keep it on a Battery tender..

I am thinking the Alternator might be going

Also it looks like the LT1/4 Alternator which is a 140A will work in place of the 124A.. I did that on my 89, I think that might be a good route to go..

any thoughts??

[Dynomite]

If you have NO DEAD cells in the battery and your alternator is putting out 13.5 - 14.5 volts when engine is running (just put a volt meter on battery terminals) it seems neither is an issue, however, a battery as it ages will have less capability to hold a charge so I would say time for new battery.

You might just set battery on shelf and see if it looses charge or it only looses charge when installed. The latter case may be some kind of excessive power drain in electrical system with switch off. 124 amp should be good enough unless you have added electrical components drawing high amperage which I can offer no excuse for my 200 amp alternator.

[-=Jeff=-]

If you have NO DEAD cells in the battery and your alternator is putting out 13.5 - 14.5 volts when engine is running (just put a volt meter on battery terminals) it seems neither is an issue, however, a battery as it ages will have less capability to hold a charge so I would say time for new battery. You might just set battery on shelf and see if it looses charge or it only looses charge when installed. The latter case may be some kind of excessive power drain in electrical system with switch off.

Car idling, with lights on: 13.0v at Battery using DMM

I did notice the Voltmeter in the car fluctuates more, usually sits about mid way most of the time, but sometimes lately at idle it drops lower

I will probably swap the Alt first, then the battery, unless there is a definitive test I could run without taking the battery in to test it

EDIT: I should also add, the light do dim at idle, quite noticeable too

[Dynomite]

Seems to me that if you have 13 volts at idle with lights on and prolly 13.5 - 14.5 volts at higher rpms with lights off.....I would say battery.

But you did not say what your symptoms were...I assume your battery goes dead overnight or some such but that is not possible being on a tender unless it just is not charging up...have you tested each cell with a specific gravity tester? And then with battery on bench testing specific gravity in each cell to make sure it holds a charge over night with tender not connected? Each cell of a charged battery should float 4 of those little colored balls in the specific gravity tester.

My experience with alternators is that they go FAST....loosing all output at once and not loosing a bit of voltage output over time. A battery on the other hand can get bad S L O W E L Y.

[-=Jeff=-]

Seems to me that if you have 13 volts at idle with lights on and prolly 13.5 - 14.5 volts at higher rpms with lights off.....I would say battery.

But you did not say what your symptoms were...I assume your battery goes dead overnight or some such but that is not possible being on a tender unless it just is not charging up...have you tested each cell with a specific gravity tester? And then with battery on bench testing specific gravity in each cell to make sure it holds a charge over night with tender not connected? Each cell of a charged battery should float 4 of those little colored balls in the specific gravity tester.

My experience with alternators is that they go FAST....loosing all output at once and not loosing a bit of voltage output over time. A battery on the other hand can get bad S L O W E L Y.

just noticed the voltage on the gauge int he car is reading lower then normal at times.. I might just get the battery tested. no other real sypmtom other the odd ( lower) readings on the OEM gauge

You might be right as the battery is 5 years old now

[GOLDCYLON]

Drive the car to Autozone and have them load test the battery. You will find out quick Jeff if its an internal short.

[Dynomite]

just noticed the voltage on the gauge int he car is reading lower then normal at times.. I might just get the battery tested. no other real sypmtom other the odd ( lower) readings on the OEM gauge

You might be right as the battery is 5 years old now

I am not sure if you have a sealed (no maintenance) battery...but you can get the little specific gravity tester at any local auto parts store for a couple bucks. Or WallyMart will be happy to test the battery for you.

Have the battery tested after it has been tended on a bench to eliminate the possibility of an electrical issue in your ZR1 with ignition switch off if you are testing by specific gravity. You may think you are tending the battery installed but it is draining as fast as you are tending.

[-=Jeff=-]

I am not sure if you have a sealed (no maintenance) battery...but you can get the little specific gravity tester at any local auto parts store for a couple bucks. Or WallyMart will be happy to test the battery for you.

Have the battery tested after it has been tended on a bench to eliminate the possibility of an electrical issue in your ZR1 with ignition switch off if you are testing by specific gravity. You may think you are tending the battery installed but it is draining as fast as you are tending.

right but every other car I have had with a no maintenance battery like clock work.. 4.5 to 5 years.. battery is done

I doubt it is an internal issue on my Z.. I just noticed it, but I have not driven the car in a couple weeks either. Again, I do know my Optima is 5 years old might even be 6 years. I will get it tested and go from there. When I was working on the windows this past couple months I drained the battery once or twice ( not to dead) but down to maybe 9-10 volts ( guessing)

only thing I noticed was the OEM gauge reading

[GOLDCYLON]

I am not sure if you have a sealed (no maintenance) battery...but you can get the little specific gravity tester at any local auto parts store for a couple bucks. Or WallyMart will be happy to test the battery for you.

Have the battery tested after it has been tended on a bench to eliminate the possibility of an electrical issue in your ZR1 with ignition switch off if you are testing by specific gravity. You may think you are tending the battery installed but it is draining as fast as you are tending.

I know my battery is about 5 years old and is an Optima red top, I always keep it on a Battery tender..



Im pretty sure all the Optimas are sealed so he wont be able to go cell to cell to check the specific gravity

[Dynomite]

Im pretty sure all the Optimas are sealed so he wont be able to go cell to cell to check the specific gravity

Your advice is BEST :thumbsup: Get a battery load test ;)

[tomtom72]

I thought that the Optima's were "gel-cells"? How do you do a S-G test on a gel electrolyte?:redface:

My gold top A/Zone battery is just starting to yield the same symptoms as yours. Mine is 4.5 yrs old. I had to look up my receipt as I forgot how old it was exactly.

Your test of the alternator's output seems to be well within the specs. A load test would be best. I would suspect that if you can't recall exactly how old the battery is, that it is 5 or 5+ yrs old.....usually we remember spending big doe and getting short changed....that it is past it's prime. just my two cents.:redface:

This was told to me by an Interstate rep a looooong time ago, so fwiw. Usually the electrolyte only has so much life. The reaction due to the charge/discharge cycle creates salt which collects at the bottom of the case and eventually reaches the bottom of the plates and thus creates a short across two plates. The better the salt connection, the better the short. The longer the posted life of the battery, the bigger the space from the bottom of the case to the bottom of the plates. Taken together these two circumstances kill the battery's ability to hold a charge and have output. I don't know if this applies to a Gel-Cell type battery with spiral plates, but the chemical reactions that take place have to be analogous and the "plates" still have to be suspended for it to be a battery.

:cheers:
Tom

[-=Jeff=-]

Yeah I figure a battery is a good start.. then if needed I will swap the Alt.

So what is the recommended Battery. I don't need to have a NCRS Correct battery

[-=Jeff=-]

Oh, I will probably run the car with the AC Compressor on and check the Voltage too..

that is when I noticed it yesterday with the gauge as I was running Defrost

[tomtom72]

That's how I check mine...kind of. I don't have a load tester either. I usually start the car and let it recover then I turn stuff on progressively and take a V reading after each accessory is on. :dontknow:

My gold top was expensive, almost $80.00(?) when new. It didn't fit without me doing some trimming to the part of the case that forms the holder for the built in strap. It stuck out too far and I couldn't get the gill panel to sit right. So, I give the A/Z battery a C+ in the value dept. To be fair it lives in an abusive environment. The car is only used about 5k miles a yr., and that is hard on a battery.

I just don't know what other brand I have confidence in to tell another person to buy. I may just do a price comparo of 5 yr batteries and try something in the middle of the price range of all the brand name ones???

:cheers:
Tom

[gbrtng]

Yeah I figure a battery is a good start.. then if needed I will swap the Alt.

So what is the recommended Battery. I don't need to have a NCRS Correct battery

WalMart's are guaranteed for 3 years free replacement - made by Johnson Controls just like the current ACDelcos, but better warrantee.

[Dynomite]

WalMart's are guaranteed for 3 years free replacement - made by Johnson Controls just like the current ACDelcos, but better warrantee.

I like WalMart's guarantee......and any WalMart will replace a battery.
Do you know which WalMart battery FITS without modifications?

[Ccmano]

WalMart's are guaranteed for 3 years free replacement - made by Johnson Controls just like the current ACDelcos, but better warrantee.

:iamwithst that's what I did... as for your battery, get it checked, there is no other way to know. A battery can have good voltage and still be bad.
H
:cheers:

[batchman]

How many miles on the car?

I don't know GMs charging setup but my experience has been as you run up miles, alternator brushes will wear and give less output at idle/low rpm. A car with an idiot light will show this first as a low glow at idle. The last several I've had to worry about were at 120-150k miles or so.

The other popular alt failure is in regulation, which is often integrated into the alt, which will be a sudden total failure.

Good luck,
- Jeff

[-=Jeff=-]

How many miles on the car?

I don't know GMs charging setup but my experience has been as you run up miles, alternator brushes will wear and give less output at idle/low rpm. A car with an idiot light will show this first as a low glow at idle. The last several I've had to worry about were at 120-150k miles or so.

The other popular alt failure is in regulation, which is often integrated into the alt, which will be a sudden total failure.

Good luck,
- Jeff
63K miles

[gbrtng]

:iamwithst that's what I did... as for your battery, get it checked, there is no other way to know. A battery can have good voltage and still be bad.
H
:cheers:

My local WalMart has a hand-held tester which is hooked to the battery terminals and in about two minutes a thermal paper printout gives the battery analysis. I'm guessing it does a load test at about 20 amps and watches the voltage drop over time. The test is done in the vehicle with the battery terminals connected. If the test says fail, replace battery you get a new one if the original Wally battery is newer than 3 years - no charge.

And the C4 uses a group 72 battery - just get one with enough cold cranking amps.

[dbriana]

I had to replace my alternator around 36k.

[-=Jeff=-]

Okay did some testing but the motor was freshly started and not warmed up during these measurements.

Also I have an aftermarket Stereo with an amp..

Here is what I got using my DMM connected to the battery:

Key on: 12.5v
Starting: 10.5v

Following are while running:

No Extra Acc: 14.7
Headlights On: 14.68
A/C & Lights: 14.6
A/C & Lights and Radio: 14.0v

same as above while watching A/C Compressor cycle on: 13.5v

Shouldn't the Alt hold the charge? or is it all owed to fall, Granted I need to redot he tests after it is warm too..

these were all done at idle, although I did increase the idle spedd a bit to see if thee was any change and there as not

[Paul Workman]

Jeff,

It appears you don't have any shorted cells, and the the alt and regulator are working OK. (The 1 volt drop with the compressor on may be within the normal voltage drop across the wiring between the alt and the battery. In any case, the alt appears to be working normally.)

You can go to Wally World (or perhaps AutoZone) and have them load test the battery. If the battery is 5-6 years old, it will not likely hold voltage under a load test (usually about 150 to 200 amperes over 10 seconds is a common test). Usually, if the voltage drops much below 10 volts after 10 seconds, the battery is in that twilight area. But, if it is at or below 8 volts after 10 seconds, the battery is kaput!

Wally World will put it on their machine which will bring the battery up to full charge first (for proper testing), and then load it to see if it will hold the voltage in the "green" zone - a pretty good test.:thumbsup:

Hope this helps.

P.