How old is the battery? Does it have removable caps as to stick a hydrometer in them? Just curious as to the varying charging rates you have.

 

generally, a shop will check the battery. If it passes they will check the alternator output. if its no good they will check the field voltage signal from the ecm. it that's good...they will replace the alternator.

 

I have two AGM batteries, so they are completely sealed and are not the typical lead acid batteries. They varying charging rates was new information for me. I know that my 07 Tahoe has some type of charging program that will only charge the battery when its below a certain voltgage to help save fuel, if I'm not mistaken.

Thanks tech2!

Just an update, just as I expected the alternator delivery was delayed till tomorrow. At first thing this morning it says it was out on the truck for delivery, but 2 hours into my drive home, it says it was delayed. I dont know why, the roads were fine, clear and mostly dry.

 

Bad alternator; I was amazed how the pulley bearing felt, it was still buttery smooth after 12 years and ~263K miles...

The new alternator in place, I wish it would stay clean like that, lol.

Charging voltage from altenator, on a cold start...

Charging voltage from alternator after engine was warmed up.
Hi all, just finished the install earlier this afternoon. Removal went fairly smooth, until I tried to use a screw driver as a pry bar to free the bad alternator. Then I remembered I have a ball joint seperator and used that as a pry bar. Then the next hard part was getting in the new alternator as it is a tight fit. Once I started to get it seated, there was no way pounding it with my hand would have gotten it seated the rest of the way, so I used a rubber mallet. I hope its safe to tap in the alternator in with the rubber mallet, I know there may be some sensitive electronics built into the alternator.

Next hard part for me was getting the bolt holes lined up properly so the bolts would bite down on the threads of the alternator mounts. It was alot of tapping and prying back up, but I finally got the bolts tightened down.
Then I just buttoned everything up. Started up the car, and first good sign was the battery light and service battery charging system were not on. But the charging voltage was reading high for a few minutes, then it seemed to go back to a normal range after the car warmed up.

I drove it about 10 miles and all seems fine so far. *fingers crossed*

Thank for anyone who offered advice and technical support!

 

I would've ground the alternator a tad narrower to get it to fit. I've had to do similar on bottom shock absorber ends. Sad.

 

if you continue to experience any issues, don't hesitate to replace the negative ground cable and the positive cable from battery to mega-fuse / Starter, I had all kinds of random dead battery issues that were all due to a bad neg cable that looked perfectly fine and even would ohm out okay as long as you didn't move the cable...

 

Even if I had a grinder I don't think that thought would have ever occurred to me! lol! Thanks for tip!

Thanks for the tip in2pro! That's an odd issue, but I'l glad I'm aware of it now. So just an update, car has been driving fine, and no more alternator issues at all!

Now lets see what goes bad next on my Tahoe....

 

A bench grinder is a really handy tool. I've also sharpened stuff such as mower blades, ground down box wrenches for more access, etc. Just be sure to ALWAYS wear safety glasses and watch your hands using this.

 

no grinding required.

the alternator has sliding threaded bushings that wedge tight when its installed...that's how its designed. next time...place the alternator on a bench....thread the bolt into the alternator and support the ear of the alternator...tap the bolt with a hammer to slide the bushing back...and the alternator will slide into place.

 

Hello I know this is un related .I dont Kno how to start a new thread