genestoy

I noticed something yesterday that I had not seen before and was wondering is anybody knows why this happened. We just returned from a 1500 mile trip and all was well. I drove the Yukon the day after we returned and noticed the amp guage was at about 10-11 volts (halfway between the first mark and the 14 volt mark). This continued until I stopped. The Yukon was off for about 3 hours then started again and the guage went to a little past the 14 volt mark, then soon went back to the 10-11 volt area. The Yukon sat overnight and I just drove it about 2 miles and it is back to the 14+ volt mark area. We are going on another extended trip soon and am a little concerned about this. I know it is under warrenty but just wanted to see if anybody has had similar experiences and what might be the cause.
Thanks

73shark

The alternator basically shuts down when it's determined that it's not needed. I've noticed the same thing and Dave explained this awhile back. It's kind of scary for us old guys. []

genestoy

Thanks for the quick reply. I kind of thought that might be the case but never noticed that before. Like you said it was kind of scary and I thought that something was wrong. Everything seemed to be working fine though.

loulblades

First off, you are referring to the voltmeter.

I have been through this before.

First check all your connections(clean and tighten). Chassis ground etc. (do the cheap stuff first)

After that it's either the battery or alternator (of course we are assuming that the meter is good) not keeping up. If you have a multimeter, check the voltage yourself. Since it came back after sitting awhile this kinda points to the alt (the battery is recovering) but then again that is not definite.

Take it to your local auto parts place and have them do a load test.

If the batteryis badand it totally craps out, you will most likely need to replace both alt and battery. In the 5 years or so that I have owned my Tahoe, I have gone through 3 or 4 alts (2 in 1 weekend) and at least 3 batteries (the best battery at wallyworld is still a cheap battery). No more cheap alts or batteries for me.

One other thing, if this is an old Delco battery (not sure the years) there was an issue of theterminal rotting inside the battery.

genestoy

I guess you didn't notice my sig. I have a 07 Yukon with 10,000 miles, virtually new. Everything is tight and I did check with a digital voltmeter, but of course right now it is above the 14 volts. They made many changes in the new Yukons and Tahoes so that is why I asked the question. My two previous Yukons had only one battery replacement each in the 3 yrs I owned them (common here in AZ) and have never replaced an alternator.

loulblades

Yes I didn't notice that you had an '07. Guess I thought I was in another forum that is related to my year.

No matter what year, I still would be concerned if the voltage went to 10 volts.

BMoTahoe

73shark is right on the money. With all of the technology built into the new Hoes and Kons (cute, huh) the alternator actually knows when it's not needed. The pulley still turns, but the benerator doesn't put out. Do this, sit parked for about 20 minutes with the engine running and the radio playing (or better yet, if you have a nav'dvd combo, with a movie playing) and watch the volt meter. It will fluctuate between 10-14 volts as the alternator senses the drop in batery power. It's normal and a built in function.

e

2nd, the on/off thingy.you can also notice this cycling sitting in traffic at night. You can see the lights pluse when the Alternator turns off/on. I have not noticed that big of a drop in voltage when this happens looking at the guage.
A drop from 14 to 12 on the guage would not be that noticeable orbring to muchattention to itselfbut going from 14 to 10 is a different story.
I would meter the battery right after turning the truck off. Leave it set overnightand check the voltage at the battery before starting it. If its under 12v I would bring the battery to have it checked out.......

BMoTahoe

On/of thingy ?

e

Alternator turning on/off.....