First time poster, long time Tahoe owner needs help please

[offthehook67]

99 Tahoe w/5.7 ltr 4wd and 141,000 miles

Last week I noticed my (dummy) battery light kinda blinking on after starting the truck. My first thought was the battery was going bad.

I took out my volt meter and tested it running to see if it was getting a charge from the alternator. While running I was getting over 14 volts. So I am thinking battery again. Test without running and it was quickly dropping below 12 volts.

To verify my thoughts I ran to Auto Zone and had them test the battery. They did it with the vehicle turned off and came up with the same conclusion (Bad battery)

So I purchase a new one, go home and install it. Go to start the truck and "Click" notta nothing. I go back around the front and give the terminal connections a little more tightening. (side posts) Try again and it started but seemed like a tough start/turn over of engine. So being a new battery with a 11/14 sticker on it I pull the truck out of the garage and park in driveway. The next day I go to run errands around 2pm and again "Click"

I am like "Really"

So I put the old battery back in and still "Click" notta. Grab my charger and set to cold assist. Go to start and still "Click" give it another minute and try again and it started with of course the battery light on.

I run back over to Auto Zone and they check the alternator this time. Putting out just over 14 volts as when I did the test myself. I have the battery I bought in the truck so he tests that new battery. Shows it has a 54% charge.

I exchange the battery and head home. Install the new one (again) and this time it starts right away but again the (dummy) battery light is on. WTH? scratching my head. Well I still had the errands to run so I head out and within say 5-8 minutes of driving the light goes off. Hmmmm I think to myself....

So yesterday morning I start it again and sure enough the battery light is on. Well crap ola! Well I was heading deer hunting for the morning with my dad and he pulls up. I shut off my truck and leave.

Last night after being back home for a few hours from hunting I decide to run out. I fire up my truck and again of course the light is on. I drive it for roughly 5-7 minutes and it went out.

So this morning I run a test. I test it with my volt meter before I started it. Reading was 12.30 ish volts. I start the truck and yes, battery light is on. I test again with it running and I got a reading of 14.36 volts.

Now before you send all the ideas my way keep in mind I have made sure that not one accessory was left turned on to draw amperage. ie radio, fan, interior lighting etc etc. I have triple checked that over and over the past few days.

In the back of my mind I am wondering if the alternator is fooling me so to speak? Have never had this issue before. Or I am thinking the starter could be the cause due to the "Click" but I am leaning more towards the alternator even though it says it is putting out over 14 volts.

Any and all help is appreciated as this one has me going

Thanks in advance.

 

[tahoe.mkIII]

bad battery?i had gotten a brand new, defective die hard battery once. it would take a charge and voltage would drop very slowly when the engine was off.checked everything else, thinking that the brand new battery was ok.it wasn't.got it load tested. had a bad cell...so assuming you know that the battery is ok id suggest you check the starter(if you tap the starter with a hammer will it start?).or maybe a bad ground/connection somewhere?the starter ground strap can get rather crusty.

 

[MarkD51]

I'm no electrical expert, and hate when odd shit like this happens.

I would check and suspect any-all wiring and connections to and from alternator, battery, and starter.

On my own Tahoe once had loose connections at the starter fooling me into thinking my starter was going.

Was getting the click-click, went underneath to see what would be involved for me to sap out a starter, and the connections were very loose, and looked dirty as well. A wire brush, some contact cleaner spray and wrenches solved that problem.

Things get filthy down there quickly, and with vibration also a possible bad connection occurs. For sure wouldn't hurt cleaning starter terminals, and all other connections. An ohm meter here and there might be of use?

That sometimes a cable or wire might look OK, but have a short or bad connection due to corrosion. Check the battery cables, and ground wiring.

Other suspects might be a starter going?

As well, do check as you say, any possible parasitic issues, sometimes a light somewhere such as an underhood light, glove box light might be staying on somehow. They can be foolers.

Hope you get this issue solved, do keep us all posted.
Mark

 

[99Vortec]

If you replaced the battery, and initially got a "Click" from the starter, then I would lean towards a starter/wiring problem and NOT an alternator problem.

Good Luck.

 

[livingez_123]

could have a bad Diode in the alt