Need Help - Electrical Issue

jtupper · June 13, 2012

About a year ago we started hearing engine noise coming through one of the rear left speakers on the wife's 08 Yukon XL. It's that high pitched whine that goes up and down with RPM's. It was happening intermittently and would go away do it wasn't really high on the prority list. Well, a few weeks ago we noticed that it got louder and was coming from both sides, still intermittently though. I'm thinking it's a grounding issue.

We went on vacation to Destin last week and while we were there, I noticed that the a/c would kind of cut out for just a second, so I'm thinking the a/c might be getting ready to go. Later, I noticed that the stereo system would just turn off randomly and turn back on. I also noticed that the truck sort of stalled for a split second when this happened, but not to the point that you had to restart the truck. I was kind of worried about getting stuck on the side of the road on the way home. At any rate, we made it home without issue. The stereo system has turned off a few times since then, but I haven't noticed the "stall" that came with it in Destin.

As for the a/c, a few months ago the a/c belt broke for no reason. When I replaced it, I was wondering if I have a slugging issue going on with the compressor. I had a 00 Tahoe that had this happen, but not with only 70k on the clock. It's possible the a/c and stereo could be unrelated, but it's a big conicidence that it's happening together.

Obviously, I'm out of warranty, exept for powertrain. I really don't want to give the dealer a blank check to spend hours on end chasing a problem I can't duplicate on demand.

I don't even know where to begin. Anyone have any ideas?

scooby5121 · June 13, 2012

Just for the A/C , when the gas is low the unit will shut down.

Have it topped off by purchasing the kit to recharge the A/C.

Scooby

waumo1 · June 13, 2012

Our 2002 Yukon had a several ground straps on underneath on the exhaust etc. I would take these all loose clean the connections and reinstall. Also the ground wires going to the body/chassis. In particular if there is a ground wire from the PCM.

Gurrzt · June 14, 2012

Usually the high pitch whine through the speakers going up and down with the rpm would indicate a bad spark plug wire shielding.

jtupper · June 14, 2012

I will look into the ground straps.

I did some more searching last night and found where a few other people had this problem (alternator whine). Some stated the dealer replaced the alternator under warranty and it fixed the problem, something about a diode in it that goes bad. Some also stated that it did not fix the problem. others stated the dealer replaced the head unit.

Here are my thoughts about the alternator...if it is something to do with that a) wouldn't I have charging issues? b) couldn't I take it down to the local parts house and have the alternator checked?

I did have to replace the battery late last year, but that hardly seemed out of the ordinary for a 3 yr old vehicle (at the time).

jtupper · June 26, 2012

The saga continues...

Things have progressively gotten worse. Now when we go out out to start it, sometimes it won't start. By not start, I mean it has no power and won't turn over like the battery is dead. If you wait about 5 minutes, it will start up. The battery was replaced less than 10k miles ago.

Some other things we have noticed is that when you turn of the car, sometimes the radio turns off immediately instead of when you open the door. You can start it back up immediately and turn it back off and the radio will stay on until you open the door. I have also noticed that a lot of times when I get in the car after a short drive to the store or something, all of the a/c controls will be set at 74°, including the rear air. The fan settings will be at their lowest settings and will be set to the floor and vents. The last issue is that all of the vents will blow cold air except the two driver's vents. They will blast hot air until you turn the car off and back on again. Sometimes that doesn't fix it immediately.

I located a few of the ground straps and all seems okay.

I really need a direction to go in here. Any help is appreciated. Could it be as simple as a defective battery?

waumo1 · June 26, 2012

"Could it be as simple as a defective battery?"

Yes it can be a battery with an internal bad connection. I can also be a bad connection external to the battery. We had a 1994 Buick that would randomly stall while driving, not start and then slightly later start normally, the radio clock would reset, etc. Ultimately it turned out to a bad connection on the jumper post where the battery and other positive leads connected. The factory had used the wrong nut (where you couldn't see it) so even though the nut was tight the connection was loose. I found it by tapping around in the engine bay with a rubber mallet and I saw the underhood light blink. This was after about 5 years of no success finding it.

jtupper · June 27, 2012

It seems I may have figured out the problem. Something just kept telling me to check the battery. It turns out that the positive battery terminal was just a little bit loose. You couldn't tell by looking at it but I was able to move it back and forth to the point that I was able to remove it by hand. The battery posts are slightly tapered and the terminal wasn'r seated all the way against the bottom of the post. Personally, I think the design of these termonals is weak. There just isn't much room to really camp down on the post with it. Anyway, we'll see how that works and if it resloves the problem.

One thing that is still nagging at me is the fact that the radio would just turn off and on sometimes while driving. Even if the battery was losing connection, once the vehicle is running the alternator should power everything, right?

Are there things in these newer vehicles that are still powered by the battery even with the motor running?

VT_Z71 · June 29, 2012

Dude I had the exact same (electrical power) issues a few months back. After a couple of dealer trips and misdiagnosis, it was finally determined to be a crimped/hyper extended positive battery cable which they replaced under my extended warranty. I believe first couple of years of the GMT-900s had issues with this, might even be a TSB. I know GM redesigned the positive battery cable in the most recent years to fix the issue.

Also, like you I sometimes get the noise from my rear speakers only, although its more 'digital' sounding than alternator whine. The pitch does change with engine RPMs. Seemed to happen more frequently when I had the battery/electrical issue, now its a pretty rare occurance. Anyway, here is what i've found works for me. Whenever that noise starts, reach your arm back behind your center console and turn the RAS (Rear Audio System) on then off. That always worked for me, and so did just lightly pressing on the face of the RAS unit itself in which the noise immediately disappears. I've checked all the connections, they are all good. I think its just something funky inside the unit itself that every so often decides to cause interference.

Hope this helps.