Hi Everyone was digging around and couldn't find a answer so I am here asking for any hope if possible. I have a 2000 Pontiac Firebird WS6. I replaced the battery red top optimum battery and also replaced the alternator with a brand new AC delco 102 amps. I checked the grounds as well. After the car warms up and I have accessories such as a/c, rear defrost etc. when I am idling at a traffic light in drive the voltage on my battery dips lower to about 10 volts sometimes lower where the vehicle wants to turn off. I had both the Battery and Alternator checked. Alternator passed and battery passed as a good battery but not getting enough volts. Has anybody ran into this issue in the past? If so what was the cause? I am stuck by people giving me different answers but want to make sure I have it right.

Cheers everybody

 

With your multi meter set to volts you should be seeing 12.7 or higher on the battery and with the engine running you should be seeing 13.7 volts on the multi-meter. I'm not sure if its advisable to disconnect the battery from the running engine or not like in the old days but that's how to test to see if your alternator was good or not. You may have poor connections +/- or a faulty alternator, battery or both.

 

make sure your exciter wire is plugged back in as well or at least fully connected

 

I agree; if the battery and alternator both checked out as being good, then the exciter wire connection might possibly be marginal (this wire or connector is often damaged during alternator swaps). Having said that, it's also still possible to have an issue with the battery or alternator even if they tested as good. Sometimes issues with the alternator won't present during a typical test as they are not subjected to the same level of heat. Also, the newer Optima batteries seem to mostly be junk now, based on many reported issues by members here in the last few years, so I wouldn't necessarily trust those either.

 

My battery tested at 12.4 but wouldn't turn the car over so I just dropped about $200 for an Optima.