Hey guys I have a small problem. My alternator doesn't seem to be charging properly. I think it may be a little low on amperage, but I want your opinions.

Today, I went to start the car, it hadn't been driven since Sunday. It wouldn't start right up. I know the heat is causing the main relay, etc....this is the first time is has done that this summer. So, while I was trying to crank it, the battery ended up dead after just a minute. My car alarm probably draws a bit of juice when car is off (bright flashing light, remote monitoring, etc) but all else seems fine when I tested for parasitic draw.

The battery is also ruled out. I have a red top Optima, less than 6 months old. Will hold an excellent charge. No corrosion, no leaks, etc.

So, I charged up the battery and all is well. Now that battery is charged the car could probably sit for 2 weeks (I did that once back when I was doing paint prep, alarm on and all).

Question is (after all the background).....do I need to pick up a better alternator? The current one is the original one from the factory, 177k miles ago. I hope that this would allow the battery to get an ample charge. The current alternator passes all alternator tests on my charger as well as at autozone BTW.

 

how many amps output is the alternator putting out ??

if you are positive that there is NO parasitic draw ,, then the only way the battey would get discharged is if ,, you accidentally left some component on. battery will not hold the charge or the altrrnator not charging properly

I have seen alternators test ok intermittently many many times ,, so when you do a charging system test make sure you test it sevaral times and at different times

by the way what did you get when you did the parasitic draw?? how many amps?? how did you do the test for parasitic draw ??

Do not mean to offend you with my questions i just want to make sure you are doing it correctly and know what the amps draw should be ,, if you get a draw of more than .030 amps ,, you got a draw in the system that eventually will kill the battery ..

 

It has been a little while since I did it.....I don't have my meter anymore (it was a $500 Fluke, company owned). I put it inline on the ground side. I don't really remember what it was reading. I will check it ASAP. I may not be able to get a new meter and do it before I go to shop to get bumper painted and installed.

If it isn't too hard, can you give me a quick rundown on your recommended way to check for draw??? You won't offend me with questions....I am just an amateur, but my knowledge of electronics is pretty high, I am currently working on Electrical Engineering in school.

 

there is a write up on our DIY section .. chk for battery draw and you got it hooked up ok,, in line with the neg cable . cable off the battery post .
when you do it, give it a few minutes for electrical system to stabilize before you do the testing. make sure everyhting is shut off ..

 

Another thing to check is system voltage when it's running. Measuring parasitic current when the car's parked doesn't really say anything about the capacity of the alternator.

The one time when the alternator SHOULD have the most difficulty keeping up with demand, is idling with all possible loads turned on. You could even check this with a cheap voltmeter, here's your test...

Go for a drive so it's warmed up, let it idle with everything turned off.
Measure system voltage, easiest place is at battery posts. Should be 13v to 13.5v depending on the accuracy of your meter.

Now turn on everything you can find. Headlights, stereo, rearwindow defogger, ventilation blower, jumper your fan switch so the radiator fans run, whatever else you can imagine.

How much does the voltage decrease with all that stuff turned on? When you compare loaded & unloaded using the same meter, you sorta work around the issue of the meter's accuracy. That's the test for whether the alternator is putting out OK. If it can keep up at idle, it should be fine.

 

Ok, I am finally going to dig this thread back up.......as I finally found time to work on it.

I had the alternator tested at Autozone today, it was bad. The gauges were going crazy as well as other things while it was being tested. Should I just replace or have it rebuilt?? I would like to make it have a little more amperage if I can.

I will post later once I get it installed, hopefully everything is fixed but there may still be another problem.

 

i/d go with a Honda or Bosch alternator ......

 

Got the alternator in, seems to work ok. I don't know if my battery problem is solved yet, and I don't have time to look at it this afternoon.....so that will have to wait for a bit.

 

Just another thing....this may not be related. It seems that the car was running sluggish for the past couple weeks, now it is not after replacement of the alternator. That is the only thing I have done to the car.

Is it possible??