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=-]

Originally Posted by 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.

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=-]

Originally Posted by 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.

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]

Originally Posted by -=Jeff=-

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=-]

Originally Posted by Dynomite

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]

Originally Posted by Dynomite

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.

Originally Posted by -=Jeff=-

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]

Originally Posted by GOLDCYLON

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 Get a battery load test