So another round of possible issues on my baby. 2001 Silverado, 4x4, 4.8L reg cab 1500.

I have a feeling my alternators going but want to be sure before I go out and get a new one.

I've recently redid both the serpentine and ac belts since they were both stock (19 years old) and one of them was squealing intermittently (turned out to be the ac belt)

Ive had for awhile now if you hit "up" on the power windows the headlights and dash lights will dim while the buttons depressed then return to normal once the windows fully close or you release the buttons.

In addition, there seems to be a high pitched whine coming over the speakers that raises in pitch as the rpms increase. This whine occurs even with the stereo power set off. Press the accelerator (even when in park or neutral) and the pitch increases, release and it decreases. The whine has been happening for awhile as well, long before I did the belts.

The last thing that occurred recently was I went to start the truck, it started fine, then suddenly stalled out. I did have the blowers set to 5 with ac on. A couple start attempts like this resulted in a stall. When I switched off the blowers it started fine.

The plugs and wires are original which I plan to replace as well but I dont think they are the full culprit.

I would guess the age of the wires has their resistance higher and the age of the plugs has them not firing properly (there is some engine shudder when idling) but I have a feeling the alternator cant supply enough power to run everything and overcome the age of the wires anymore and is dying out.

Side note: She only has about 160,000km on her but the alternator plugs and wires are 19 years old original parts.

I've read unhooking the pos lead on the battery and seeing if she dies is a test but I've also read that's not a good thing to do.

I'm guessing time has taken its toll on it and shes about done.

Thoughts?

 

Check voltage at battery with meter to see what alternator is producing. I assume volt meter is 14+ on dash?
I think alternator is ok, would be suspicious you need to clean some grounds.

 

Anything that "old" is going to need replacement parts, your call, replace parts, or get rid of it. If you have a voltmeter, check the output voltage with load, i.e. headlights on, ect. Hose's, wires ect. age. My DD is a 96 Lumina, so there you go.

 

Yes dash shows 14ish volts.

Watched a couple vids on checking and did as you said, results:

Truck off: 12.40
Truck on all accessories off: 14.43
Truck on a/c and fan at max, headlights on, stereo on: 14.37

One of the vids suggested revving to 1500 rpm and testing, snagged a person to do this:

All accessories off @1500ish rpm: 14.37
All accessories same as above on @1500rpm: 14.26

Guessing it's not the alternator.

So the dimming of dash and headlights while using windows, the whine, and the stall....thoughts?


Edit: side note I forgot to mention, and this has been happening for awhile as well...

When I'm raising the windows and the headlights dim (while raising), the blower also noticeably slows in speed until the buttons are released.

You can have the windows completly rolled up and hit up again on them as well and the dash and headlights will dim briefly and the blower will slow down.

The stall I'm guessing with everything running is it's just an overload on the system and while the alternator is sending all the correct power the old plugs and wires dont fire properly so it doesnt keep the engine running due to age and resistance.

 

+1 on checking your grounds - especially the small wire off the negative battery cable that goes to the body. If it gets dirty/corroded where it attaches to the body, funny things can happen. Simple to clean - remove bolt, take small wire brush, sand paper, etc., clean both the area around body hole and the ring terminal. Also check the engine end of the negative battery cable where it bolts to the engine - oils can get between the cable terminal and the block and decrease conductivity - clean as needed.

You might want to take your negative battery cable completely off and see how much resistance there is between terminals to make sure the cable has not degraded over time. Be sure and flex the cable and watch the ohm meter. Ohm meter reading should not move. If it does, then you have a bad cable.

A little dimming of the head lights is normal when you run the power windows. A lot of dimming is not. If it still does this after you have cleaned the battery grounds, then have you battery checked to make sure it does not have a cell going bad. If the battery tests OK, then you might want to consider new power window motor/regulator assemblies since the current ones appear to be pulling too much current when they are active

Good luck!.