did i hurt my alternator?

[vash]

i commuted to work today. went to lunch and friggen left my lights on for about 1.5 hours. turned the key, car started fine. when i got home (half day @ work), went in and got changed for the gym. now my red alt light is on! maybe i wasted my alt, by making it recharge my battery? it is putting out 12.38V, measured at the battery@900rpm. light stays on at all RPM's. tranny ground cable, good and tight, clean wires at the battery and connections tight. connections at the starter are greasy but tight. i need to order a fan pulley wrench from pelican to get to the innards. but is it alt rebuild time?

damn when it rains, it pours. balky tranny shifting and now the "big red eye of death!"

[SpeedracerIndy]

Maybe it's your battery, not the alternator. Why don't you have the battery tested just to rule it out. Around here all of the big name parts places will test the battery for free, most will even do it wile the battery is still in the car (disconnected of course).

[kqw]

I agree, Battery probably is not fully charged.

[vash]

bummer, my battery is showing 12.68V. new interstate. i am gonna check the connections behind the alt, this morning.

[Early_S_Man]

Cliff,

Try cleaning the regulator Faston terminals and plug [9% pickling vinegar, distilled water, & 91% isopropyl alcohol] ... and remove the suppressor, if still so equipped, that has short cable to regulator, rectangular aluminum body that the cable from alternator plugs into ...

[Hendog]

Your battery may still be bad at 12.68 volts. Automotive electrical systems operate at 13.8 volts, we just call it 12 volts. If your battery cannot attain a high enough level, it may be dragging the alternator down and perhaps even damaging it in the end.

[ischmitz]

A good way of testing if the alternator is charging is this:

Measure the battery voltage with the engine not running but the ignition turned to RUN. You should anywhere from 13.8 Volts (fully charged battery) to something in the low 12 volts.

Now start the engine and measure again with the engine running at around 2000 RPM:

1. Voltage lower than without running engine means you are running entirely off the battery. Every additional load (head lights, high beams) will further drag the voltage down by some 10th of a volt. It is amazing how far you can get on a fully charged battery. Your car might run several hours.

2. Voltage ever so slightly higher means that you alternator or charging circuit or battery has issues. It could mean one or more of the rectifier diodes are damaged. It could be a short in the battery. The alternator does not put out enough power to really drag up your battery voltage to above 13.8 volts. If your alternator light is on you sure have some problem.

3. Voltage way high (>15 votls) means your regulator is toast and you will cook your battery to death.

4. Voltage in the low 14 volts means the alternator is putting out the correct voltage. You still could have a dead battery (internal resistance went high) that won't hold much charge.

to rule out the battery you can have it tested (mostly free of charge) at Sears or Kragen out of the car. This is the only sure way to estimate how much capacity the battery has left and what its condition is.

Cheers,
Ingo

[vash]

thanks, after exhausting most options (the free ones), i took the alt out and had it tested. it was bad. actually looking at it at the shop, it was really crusty and required alot of work. rebuilt and looking sweet. now i am just waiting for my fan and housing to get back from the powdercoater. pictures later!

cliff
p.s. ingo, nice stuff.

[stlrj]

Get your battery charged before you do anything else. A low battery could act as load just as headlamps and fool you into thinking you have a bad alternator.

Cheers,

Joe

[RoninLB]

Originally posted by vash
.
pictures later!

how about a pic of the noise suppressor that Warren mentioned?
I think there's a few different ones?

[vash]

ronin, here is a picture from my 75 car when warren first explained it to me. the noise suppressor is highlighted with my flashlight.
my SC looks very similar

[RoninLB]

thx.. looks like the one I pulled.