Yesterday, on freeway, car started surging, cutting out, after about 5 minutes, I noticed tach and speedo at zero, voltmeter at about 10. Limped home barely, pulled battery and cleaned terminals, charged all night. Started OK this morning, by about noon, voltage was down to 12, car was hard starting, recharged, went to store and bought new battery (Autozone told me battey had dead cell). Installed, started fine; after about 2 hours, going down again (hard starting, lower reading on idiot gauge) , seemed like standard symptoms of bad alt. Here's where I'm getting confused.
Voltmeter on battery posts at idle is 13.85, steady, no change when you up the RPM. This is with the fan running on high. If my alt was OK, what should this reading be?
When i had toe original failure, my "air bag" light came on, and is still on. Assuming I can get the charging system fixed, can I clear this light?
I appreciate any and all help.
Dale - '94 GT