alternator replaced - still issues
 

Hi everyone

I got the battery and brake lights on, and I replaced the alternator as voltage at idle was below 12V at the battery.
With the new alternator there were no lights, but the car died later that day with drained battery.
I put a different charged battery and measured the voltage at the battery - it was again below 12V with the new alternator

What puzzle me is that there is no warning lights - no battery+brake lights!?
I checked the two fuses - 120A and the 7.5 (battery/alt) - they were fine.
I also measured the resistance (connectivity) from alt battery-terminal to battery plus - was ~1Ohm
The resistance from alternator casing to battey-minus also shows good connectivity

Any ideas what might be wrong - if it is defective alternator - why the battery+brake lights are not showing up ?

Have you checked your grounds? My old battery cable became loose even if it was tightened all the way just by design the thing lost clamping power by being tightened too many times over the years and eventually led to dead batteries. The ground points on the engine and chassis build up with corrosion and need sanded/cleaned up over time as well too.
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If battery is good, alternatorais good, all your connections are good, fuses are good, next guess would be ignition switch but I'm betting the problem is somewhere with a corroded or insufficiently tight of a connection

Are your gauges working? There's a 7.5 amp fuse that keeps the gauges from working AND a perfectly fine alternator from charging the battery. When replacing the alternator, there's something in the area that shorts out after driving or maybe even right away that pops the fuse.

After charging completely my battery I went to work on this issue a bit more.

So I put the battery in the car -

• measured 13.0V(engine off) as it was just coming off the charger.
• Checked all the combinations between the alternator and battery (engine off) - got the same battery voltage within 0.02V -no obvious issues with the connections (ground and battery voltage routes)
• fuses were checked the previous day
• Turned the ignition on (engine off) - all lights were on including the battery light was on - good, the bulb is not burnt.
• Turned the engine on - voltage at battery was 15.0V - a bit high, but at-least it is charging.

Drove the car a couple of miles, let it sit for an hour and problem is back - no charging!

• battery is at 12.33V
• ignition on (engine off) - all lights are on EXCEPT the battery light
• engine ON - voltage at 12.0V - battery+brake lights are NOT illuminated

SM says "Damaged IC regulator,replace" when - ignition on, engine off, the battery light is off, and the bulb&fuse are OK.
Is that the voltage regulator in the alternator ?