i have a 2000 durango....my problem is the battery gauge goes to 8 sometimes while driving....i had battery checked and came back good.....took alternator off and had checked came back good at auto zone......bought brand new battery connectors and put them on...followed my ground wire to body and made sure it was tight......In the morning when i start it the gauge goes to center and stays till i turn on heater/radio/lights then it starts to drop to 8 if i turn them off it SOMETIMES goes back up.....right now as i speak the durango is dead...it wont start at all...i had drove it bout 15 min to pick up kids from school and gauge stayed at 8 whole time......i was told there could be bad brushes in alternaor and even thou it was tested and came back good it seeems that was cause sometimes i get lucky and it will go to center and stay even with heat or radio on......please help me i am totally lost!!!

 

sounds like a failing alternator/regulator.

Quite common.

 

I concur. You should be running on the voltage the alt provides. It sounds like you may be "passing" the absolute bare minimums and when you put a load on it...it falls away and the battery is carrying you. I had a 96 Chevy S10 that had an alternator go. I was driving down the road and when I looked down....I was watching the voltage drop. Turned off the radio and the AC ... as I drove the voltage just kept sinking slowly until the battery died just as rolled into the garage. New alt fixed it.

 

Yeah.. my Bronco was opposite - everytime you hit that thing that makes you go faster - the voltage would spike up. Heck I got it up to 18v!

It’s usually the voltage regulator that goes.. but most folk replace the whole unit because most the time it’s built into the alternator but if not, it’s good practice to replace both at the same time as nothing lasts forever and they are cheap.

 

How old is the battery? Life span of a battery is 3 to 5 years. How is the battery being tested? We use the GR8 mopar battery changer/tester for the battery and checking the alternator output.

 

Battery is 2 years old.....battery was tested at auto zone while in vehicle.....as i said last night it died and wouldnt start...this morning i go out an starts up........im thinking its alt. too cause it seems i am running on bare min. and went i put a load on it such as lights or heater it drops......but alt was tested and came back good.....but have read that it has to be checked during the time of the truck failing......is there a way to check alt myself to see if it is?....i already pulled it off once.....

 

Are you having cold temp in your area?

 

yes we are......its been in the 20's lately........just weird that sometimes it will go to 14 and stay and otha times it will drop to 8 an not go back up.......

 

I used to work at autozone, So I know this little "Trick".

"When a customer complains of alt failure with loads on, Test the cars alt with the lights on or what not, See if it fails then. any good ones shouldn't fail. Our duratester will not put a great enough load onto the alt to make it fail in most situations."

^^ That was in my orientation when I started.

So Tell them you wanna do a alt test on car, Then start it, Turn on the defrosters and lights. Then see what happens.

 

Good information, Thank you.