I have a 2000 LT 4x4 Blazer with 106K on it and lately I have notice the following problem.

When I start the blazer the charging gage inside the vech shows the needle a little on the discharge side (Never has done this before) and sometimes it is straight up on gage or a little over (Where it use to be). And I have notice the gage getting worse as I start the blazer a couple of times in a row. I can hear the Alt making the whiring noise for awhile. When I put my muti-meter on the battery while running it starts off at around the 14.7 votes and starts dropping to around 14.3. the Alt starts around 14.8 while running and drops to around the same as the Bat, maybe a tick higher. So all appears to be good in that respect, however the gage in the blazer is not reflective of that and it appears that the charge is getting worse as time goes and repeated starts. (Mind you I always let the blazer run until the alt stops making it whiring noise).

Now after this is done I put the battery on a charger and it takes about 20-30 mintues at a deep charging cycle 12 volts to bring the battery back up to stuff. When I touch the wires on the charger they are hot, real hot, never had that problem before either.

There is something going on here and I just can't put my finger on it. The battery is about 3 yrs old, it is the delco yellow top kind. I live in AZ and I know thats about the life of a battery here in the desert with the summer heat. But my muti-meter just isn't showing that or the Alt...( and its about 3 yrs old also).

I have repeated these steps at least 4 or 5 times trying to find the problem. Bad gage? Battery going? Alt going? I really don't want to just part change to "Slove" the problem but rather find the problem...Any ideas?

Thanks

 

mine started making the whirring noises about December, but the voltages were good (14.8 to 14.3)
I bought a used alternator from the local salvage yard the bearings were a lot quieter that the one I had they both are identical and same amps, but this used on run about 14.5 to 13.4 volts, so I swapped out the voltage regulators and the used one went to 14.8 to 14.3, new voltage regulators are available at most of the parts store $31.99 (I am too cheap to buy a new one) (special note they are soldered on) I don't know if this helps any.

no another note I got the used alternator for $50 (105 amp) Delphi, my battery is about 18 months old and is much larger than what is called for on a blazer. but was trading off cars and the one in the blazer was 4 years old. it's a Wal-Mart battery so it might be the best move I made, but it made sense when I was swapping them, I may still need a new battery before the summer is done.

 

The easiest thing to do right now is to take the battery in to parts store to have it checked. 2 different stores would be better.
I cant explain why your dash gauge shows different than what your see on the DVM, except that it indicates what the Engine computer sees and communicates to the cluster through the data link. So.. it COULD be a bad indicator.

Resolve that by having AZ put a scan tool on it and read out the charging voltage data directly. If it shows correctly, there you have it.

 

Thanks all for your info...I will continue to watch the votage and see where it takes me, after I have the battery tested..With just me (Wife is house bound with a broken leg and a bad break, both bones about where your shin bone is. She fell off a ladder inside the house and her leg hit the coffee table. She now has a plate and 8 screws in her left leg. AAAAAAAAND...Just got her back out of the hospital, the wound got infeced and they had to open the leg up again..its been fun, its been real, but not real fun!) Anyhow I can't test it under a load because of the wife or I might be able to see if the battery is going bad...

Thanks Again