before i pull the alternator

[Crunchy]

OK four or so months ago the battery on the wife's Navigator died.  I suspected the alternator at first because I had replaced it five or so years ago.  I pulled the alternator (*^($@! and had it checked at Schucks.  They said it tested fine.  I didnt have complete confidence in the new guy running the test.  So I put it back in and bought a new battery (Sears Platium Diehard).  Four months or so later the new battery is now dying.  I charged it today for several hours and she fired right up.  Wife went out for a drive and on the way home the car was dying.  Sounds to me that the alternator isnt charging the battery.  Other ideas before I pulled that sucker out again?  The battery terminal connections are good.

[Heredoggydoggy]

Sounds more like a Voltage Regulator problem.... 

[Skyvalhunter]

you should be able to disconnect the postive  on the battery and the car should run off the alternator. if it dies your alternator is bad.

[Bradyfc]

you should be able to disconnect the postive  on the battery and the car should run off the alternator. if it dies your alternator is bad.

if you do that you take a chance of blowing the diodes in the alternator.

[Skyvalhunter]

Well then you make a suggestion then since you know so much. Meet: You are ignoring this user.

[coachcw]

not a good idea to pull battery cable running , can cause a high voltage issue. through a volt meter across the battery running you should see 14.1 to 14.5 volts then turn on head lamps and heater if voltage drops bellow 13.9 you have a aleternator problem . also verifiy votage at battery vs aternator battery post , they should be within a coupe tenths . most alternators are internally regulated nowdays .

[Crunchy]

Looks like I am going to have to pull the alternator and get it checked again, if (more than likely) it has an internal regulator 

[Bradyfc]

Well then you make a suggestion then!!!!!

i was just trying to save the the guy the extra headache no need taking it personal 

[coachcw]

some thimes when you pull an alternator and check it it will work , like a short brush or connection . run that voltage test if its at battery voltage give the at a tap with a hammer and see if it starts charging.

[huntnphool]

Just check the output of the alternator, on the output post and at the battery with a multimeter. When at the battery check both the battery post as well as the cable connector itself. Test output without any accessories running and then with headlights and heater, wipers etc, for any drop under load. If the alternator/regulator is bad it will be obvious.

[jackelope]

What do you mean when you say the car was dying?
Usually an alternator goes south, battery light comes on, volt gauge drops(if equipped), car runs off the battery till the battery is dead then the car stalls and will not restart. It will have no battery power.
When you say... the car was dying, I think... the car was stalling. An alternator, in my experience, won't cause a car to stall multiple times while driving.

[woowoo]

Sell it, buy a Chevy, and quit going to Schmucks!    Serious though, check the alt. output with a meter.   

[Mudman]

If the alt. you bought 5 years ago was a schmucks.  If so its a concern.

[Crunchy]

Well I made quick work of pulling the alternator and took it to autozone.  They tested it and its fine.  The test they ran also checked the voltage regulator and rectifier?  Anyways they ran it three times and passed all three.  So just finished slapping that sucker back in.  I am going to clean up the battery connections while the battery charges overnight.  See if that may have been it.  If not I am out of ideas.

[Crunchy]

What do you mean when you say the car was dying?
Usually an alternator goes south, battery light comes on, volt gauge drops(if equipped), car runs off the battery till the battery is dead then the car stalls and will not restart. It will have no battery power.
When you say... the car was dying, I think... the car was stalling. An alternator, in my experience, won't cause a car to stall multiple times while driving.

Yes it was stalling and the lights were dimming.  the wife limped it home.  The the battery light came on as well.   I charged it the first time and the battery light went off when it was fully charged.  it was back on when she got home.  The positive terminal connector did not look great.  I will either clean it up or replace it tomorrow.