New alternator, flickering lights

[Timc9516]

Ok so i have a 2003 yukon xl 1500 denali
backstory time. Sunday i had to go to the store so I remote started my truck and when I got in it I seen battery not charging message on the dashing the battery light so I did a short test drive and it started charging again. So I kept going I went to the store did my shopping and when I came out I remote started the truck and it was charging fine. The next day I remote start my truck before leaving for work and when I got in it it said service stability, abs, brake, battery light, and when I cleared service stability it said battery not charging so I reved it up and it started charging. So I went to work and scanned it and I had p1637 generator l terminal circuit and 2 communication codes(which I figured was because of the low battery from not charging) also I checked the generator duty % and it was bouncing from 5% to 98%. So after work I started up and it wasn't charging again so I checked the brown wire at the plug and had 10v unplugged and 1.2 plugged in. Checked the stud and had battery voltage. I reved it up again and it started charging. I went to leave for work this morning and when I started it it said battery not charging so I reved it and it didn't charge so I did a short test drive and it still didn't charge. I don't live far from the shop so I drove to work and it didn't charge at all. So I ordered a reman alternator and put it in after work.

So here's where my question comes in. After changing the alternator and charging the battery every light on the truck flickers at a slow pace at idle and speeds up when you give it gas. My first thought was bad reman so I took it back to advance and had them test it and it tested good so I cleaned the ground and hot at the alternator and the battery and I tested the battery and it read good. I was still getting the flickering so I bought a belt because the old one was starting to crack. And its still doing it. So any idea what the problem could be. I don't have the money to load the parts Canon. And to be honest I'm stumped. I work on school buses and they don't have all these fancy circuits for the alternator

 

[OR VietVet]

The alternator may test good and show charging but I would bet the regulator is failing. There is a difference between rebuilt alternators and reman alternators. A rebuilt, in my old shop days, was an old alternator that is a core that has components tested and replace or repair what is bad and clean it up and sell it as a rebuilt alternator. A reman alternator is a gutted old used alternator case that is cleaned up and has new components throughout the case. I can't believe that if you told the parts guy what the new alternator was doing, he/she did not swap it out for another one. Get an AC Delco/GM alternator and call it good. Did you have to swap pulleys when you installed the new alternator or did it come with a pulley on it and did you check to make sure was the same size pulley? Make sure the stud(s) sticking out the back and the plug in's are tight and don't move around.

 

[Doubeleive]

I would exchange the alternator just to rule it out, it could be spiking millivolts, which I just went thru the same thing, mine was sending 18v millivolt spikes and making the ignition reboot affecting the cluster and radio, other times the cluster and tail lights would flicker, did some really weird stuff, replaced the alternator problem solved.

 

[OR VietVet]

I should mention also that the cables at the battery need to be checked for tight and clean and corrosion buildup under the insulation.

 

[Timc9516]

Definitely a reman. And it did come with a pulley but I compared them side by side and they were exactly the same. Also I already went through the battery terminals. I always pull the insulation off just to be safe. I'll try and see if they will swap it out tomorrow

 

[Tonyrodz]

Definitely a reman. And it did come with a pulley but I compared them side by side and they were exactly the same. Also I already went through the battery terminals. I always pull the insulation off just to be safe. I'll try and see if they will swap it out tomorrow

Tell them you want it exchanged--don't ask.

 

[Timc9516]

Also I should add there where two options for alternators a 105 amp and a 145 amp. I figured the denali would have the 145 amp being its almost fully loaded. I wasn't sure how to check. So I went with the 145 and it looked correct. Whats the chance I was wrong and thats my problem?

 

[Tonyrodz]

Also I should add there where two options for alternators a 105 amp and a 145 amp. I figured the denali would have the 145 amp being its almost fully loaded. I wasn't sure how to check. So I went with the 145 and it looked correct. Whats the chance I was wrong and thats my problem?

Gotta check your rpos in your glove box. It'll tell you which you have.
EDIT--Here's mine from my 03 Tahoe--
Mine is just an LS.

 

[OR VietVet]

Yep, the 145 amp is the KG3 rpo code and the 105 amp alt is K68. I also believe that the flickering may be caused by a failing/failed diode trio. But who knows for sure because sometimes when I think too much I think myself right out of the correct answer. either way, as @Tonyrodz says, tell them you want another alternator and do not ask for one.

 

[Joseph Garcia]

You may also want to check all of the grounds in the engine compartment, to be sure that they are clean and tightly connected.