i think my alternator is shot..... that sucks... so i was lookin and see that its all the way at the bottom of the engine.. are these hard to get at??? i have done many in the past but they have always been on the top of the engine or close to that... any help?

 

Yeah, get a lift and do it from the bottom.
And don't buy one of those BS lifetime Autozone / pepboys/ (insert major chain name here) units they are junk.
I've had much better luck on units with 2 year warranties or brand new ones from a reputable supplier.
I'm considered a reputable supplier.

 

i think i may have a weak alternator. the engine has been making a whining/whirring sound. the dealer said it was nothing but that is because they dont drive it every day. any thoughts on what this may be?

 

Might be bad bearings in the alt or ac compressor or power steering pump. Pop the hood and see where the whining is coming from.

~Alex

 

just to throw it out there.....i have been thinking my alternator has been going bad for a little while....it would cut out on me randomly while driving, and sometimes not start die.

anyways, long story short, i checked the battery terminals (AGAIN, because i had already checked them,) and my positive termal was fairly snug, but movable......and with a bit of corrosion between the post and terminal connector, it seemed to be enough to cut off the voltage in curves, or bumpy roads....

an old trick to test the alternator used to be to unplug the battery and see if the car stays running. if it stayed running, alty was good, and if not, then alty was bad. BUT on most newer (late 80's +) computerized cars, i do believe that this is not always the case. I believe that if you were to unplug the battery, it would shock the system enough to kill the car, or even bog the car down to where the engine kills itself.....thus giving you a bad diagnosis.

any thoughts?

 

Without knowing the exact design of the voltage regulator I would have to say that it is very bad practice to disconnect the batt with the engine running and the alt spinning - it can be and most likely is a surefire way of either damaging the alt or the car's electronics - there is no "trick" to measuring the wellbeing of the alt - start the vehicle, switch on all loads you can and measure the output voltage of the alt's terminal on the alt itself (not on the batt) - if at 3000rpm+ you measure around 13.8V to 14.5V the alt can supply the load - if at idle you still measure something higher than about 12.8V the alt is most likely OK.

One final test before pronouncing the alt OK though - stick a sensitive current meter (about 2mA range) in the line between the batt and the alt's output terminal with the engine and ignition off - you do not want to see any current more than 0.5mA flowing there.Mechanically its not able to exert enough torque on the motor to kill it, and if electrically it is able to kill the car (most likely) its evidence enough that it should not be attempted at all.

 

In my experiences with many different make/model cars,it does not hurt the electrical systems at all when you disconnect a battery terminal to check for a bad alty...The trick is to never reconnect the terminal back while the car is still running,the spike up in voltage/amperage will be on reconnect,not disconnect..

 

the 'trick' was for use on older cars, and was common practice at one point.

i was speaking of the voltage difference causing the engine to fail electrically. and in another case, come close to failing electrically, yet not completely....allowing the engine to bog down so far that the engine kills itself mechanically.
























see what i did there?

 

are you sure it's coming from the alternator?
there are several other items on the motor that can whine as well.
use a stethoscope type device (or a long screwdriver with the handle end at your ear) to touch each piece to hear where the noise is originating.

 

I have had one of the diodes go short in my alternator, surprisingly it still seemed to be working ok (14V on the battery under load at about 2k RPM), but it would struggle to maintain charge at idle.
The symptom was a bad whining noise which varied with engine RPM, sounded exactly like a bad/dry bearing, it was very noticeable, even inside the car. I removed the alternator expecting to replace bearings, but found they were ok. I then went searching and found the shorted diode. I replaced the diode pack and fixed the noise. It now also maintains 13.8V at idle with accessories on.

Easiest way to track down noises like you are having is to remove the drive belts one at a time until the noise goes away. (** don't run the engine too long with the water pump belt removed**).

As for removing the battery cable with the engine running, it *probably* won't cause any major problems to your ECU, car ECUs are a lot more robust than most people give them credit for, but it if does fail, they are $$$ to replace. Therefore it isn't something I would suggest trying. Also, more sensitive items like car stereos may not survive!!