I think my Alt is taking a crap but im not sure. It drives fine at normal driving conditions but once i stop at a red light my lights dim and it runs slow. I think this is a pretty good indication that its not charging properly . To get it to act properly I just hold the brake while holding it at a steady rev and it stops acting up.

 

did it ever do that before? you know, durring the day it shouldnt do it, your not running any accessories. but at night your running your lights, your heater, your rear defroster (biggest culprit) and your alternator sometimes cant keep up. its a common thing to see on all cars. what amperage is your alternator now?
alternators wont put out full power until like 2000rpm ne ways. mayb you can get a bigger alternator if your worried about it.

 

I've had the car for 5 years and its never done it before. I dont particularly remember if it did it during the day or not. its just most noticably at night of course because of the lights

 

well it could be wearin out. it could even be the cable...if it really bothers you, replace the cable cuz its cheap compared to the alternator, and if your still bothered, replace the alternator with a 105amp alternator...a good qualtiy one too.

 

I have the same problem. I rebuilt the alternator last year and even after that is was still doing the same thing, but not as bad. I also found a loose ground wire that was affecting it also. It still acts up. Sometimes it fine, but other times it still acts up from day to day.

 

question but u don't have underdrive pulley's by chance?

 

Its the original alternator so im hopin its just wearing and i just have stock pulleys. Maybe my battery just isn't charging correctly ? ill check my wires out in the meantime.

 

I have stock pullies.

 

How old is your battery? Just as an alternator wears over time (brushes wear down eventually leading to low current output), a battery can wear out too. Figure 2-3 years on a battery (depending on brand) - less if your in a cold part of the world.

 

I put a new battery, new terminal bolts and still got the same thing. A diode in the alt is prolly going bad.. oh well.

 

could it be a voltage regulator?

 

When I rebuilt my alternator, i replaced my regulator and it seemed to help a bit, but it still acts up.

 

Check the fusible link that runs from the alt to the battery.This just happened to me.I had to replace the line with a 30A inline fuse.

 

does this loose ground or missing ground wire show up as a voltage loss all the time? I'm having the same problem under a load, the alt. checks ok

 

The alt. wouldn't be responsible for making the engine run slow.. How much slower does it run at idle? A high load on the alt. could perhaps make it drop 50-100 rpm, but then something should be getting hot.. I had this happen once but it was the battery, and it got hot.. I don't think a shorted diode would constitute a load on the engine..

 

well the engine isnt really running slow but the car feels like it just wants to stall out.

 

I meant slow as in low rpm at idle, like 300-400 instead of 550-650. But I have a feeling you should be looking at something else, like ignition system, fuel system, faulty sensors, vacuum leaks, and such. Maybe try to get the computer scanned for sensor data. Just a hunch.