Battery or Alternator?

[rfiltz]

I replaced the alternator on my 92 MTX last Dec, been running fine since. Today (as I'm planning on taking a long trip tomorrow) my BATT light comes on. Checked with voltmeter and my battery shows 12.33 V at rest. When running the meter reads about 12.07 V both between the terminals and when I check directly on the alternator post.

I'm thinking bad alternator again, but could it be the battery? I thought the Alt was supposed to read like 13.7-14.7 V when car's running?

The only thing different this time is the battery light seems to stay on no matter what. Last time it was on at idle and then flickered off as the engine speed came up.

 

[Ishodu]

Sounds like the ALT again, I hope its under warranty. Also make sure to charge your battery to a voltage of 12.6 before installing a new alt.

 

[HopefulSHO]

I thought the Alt was supposed to read like 13.7-14.7 V when car's running?

It is Sounds like your alt. took a dump

 

[rfiltz]

Thanks, that's what it was, after only 5 mos on the car! Damn Carquest! The first unit I got from them proved bad out of the box (after I had installed it since they don't do testing). This time I took the new one (was under warranty) to Advance and it tested OK (so far). If this one goes, I will bite the bullet and go elsewhere.

Battery tested OK but low, so I bought a 10A charger and it good to go. Car's zipped up now and all's well, even with lights, AC, radio, radar, and a power inverter running. Voltage dropped to around 13.5-7 at idle, but quickly went up to 14.4 when revving. Only lost a day on my Memorial Day trip.

 

[Ishodu]

Good to hear your back on the road, voltage sounds good too.