This is my 1997 Escort LX; 2.0L SPI engine. The car itself, but not the engine & transmission just flipped 290K today.
Two days ago my alternator went belly up. This was confirmed by my shop & the alternator was replaced. Note for later that my battery light never came on. (The death appeared to me to be quite sudden).
Everything was fine up until today when my battery light came on as I pulled into my driveway. I will bring it back to the shop - but I don't want to bring it back & have them tell me I need new cables or something for $[too much]. So I'm just trying to sort things out.
My battery is all of a few months old (the alternator didn't show bad based on auto parts store tests when I replaced it). The connections are very clean & very tight. The belt & tensioner are good. The alternator pulley is smooth & quiet.
So here's the part that has me confused. When I put a meter on it with the car running hot at idle with everything off it shows about 14.4V at the alternator terminal. At the battery its about 14.25V. If I turn stuff on the voltage fluctuates some. The only thing that really takes it down under 14V is the cooling fan. When the cooling fan comes on it briefly drops down to about 13V but then bounces back up (with the fan still running).
I put my son in the car to rev it & watch the tach. With a bit over 14V on the meter at idle the battery light would be on. He'd rev to just under 2K rpm & the voltage would climb slightly & the light would turn off. There was a "magic" spot at about 1900 rpm where the light would trigger on or off. Yet the voltage always remained in the range of about 14.1-14.5V. There are times when the battery light will remain off at idle, but this seems to have nothing to do with the voltage readings.
I connected my laptop-based scantool and watched the input voltage as read by the scantool & that just confirmed everything I found with the meter in terms of the voltage & fluctuation.
So....I'm not actually sure if the voltage output is supposed to fluctuate as much as it does - but in most respects I'm looking at voltage measurements that don't suggest a problem, yet I have my battery light coming on. Can anyone help me with what is going on?