Alternator issue

[GeoGoGo]

Hi Everyone,

I am posting regarding what I think is a failing alternator on my 2007 TB LT 4.2 4X4. I have noticed that my volt gauge is reading just over 14 volts at start up. Within a minute or so, the gauge drops down to 11.5 while driving at highway speed. So I fired up Torq and verified that it is output is bouncing between 11.6 and 11.7 volts.

I also have had for the past one month, a kind to rattle. Loud, metallic rattle that was there at idle to about 1000 rpm. It reminded me of the sound that the a/c clutch when it would first engage. I cycled the a/c and they do not seem to be related. I thought it might be a heat shield or something like that.

Last night I noticed that sitting with the truck idling and headlights off. I hit the high beam switch and I noticed the rattle got deeper and louder; with almost a droning sound. I repeated this several times and there is a definite correlation between the high beams and the noise.

Now I am starting to think the rattle I was hearing for a month ago was coming from the alternator. Bad bearing, maybe. Now with what appears to be reduced output for it, that turning on the high beams (with the 6hi mod by the way) put more drain on the alternator, hence getting louder.

So what do you think? The logic seems sound to me. Anyone have any thoughts, ideas, suggestions, or comments I would love to hear them. Thanks everyone and have a great weekend!

Respectfully,
George D.

 

[Capote]

Definitely sounds like a bad bearing to me. I also had my original alternator drop in Voltage like that, but without the bearing noise. It's best to buy a new one before it leaves you stranded. Some places will rebuild alternators, so you could check locally for a place that will.

 

[Mounce]

I personally think the voltage and rattle are separate. The rattle is probably an exhaust component or heat shield or like in my case the ac lines for rear air (you may not have that). The reason the rattle changes with certain load is when the alternator is presented with load it boosts its power/works harder which puts a load on the motor via the belt drive and it drops RPMs a little, thus changing the sound of the rattle.

I notice a slight voltage/idle drop when rolling up the windows, especially more than one at once. Need get out and check around and locate where the noise is actually coming from.

 

[budwich]

unplug the savrc module (at the negative battery pole) and see what the alternators response is. go from there.

 

[Mooseman]

After that, to check the bearing(s), take the belt off and spin each component to check for noise or roughness.

 

[GeoGoGo]

Hi Guys,

Sorry to drag up an old thread but I have some news and I need some advice with this same issue.

I finally broke down and replaced the alternator. The squealing an d grinding had become both frightening and unbearable. Replaced the alternator and belt and it was perfect. Alternator was putting out 15ish volts, when hitting the 6 HI, the voltage would drop to 13.5 for a couple seconds and ramp right back up to 15ish solid aw a rock. Quiet as a mouse peeing on cotton! I couldn't be happier!

Fast forward to the next day. I look down and the voltmeter is reading low again. I fire up torque again and sure enough, it's putting out 11.6. I have had the battery tested at Advance and it tests fine. It has 13 volts and amazed the Advance guy (I know it doesn't take much) by showing 1100 CCA.

I am at a loss here. There are no symptoms of a low voltage condition. It cranks over just as fast as it ever has. If I stress the charging system with the A/C, seat heaters, 6 HI, rear defrosters, power steering cranked to full lock and the voltage stays solidly at 11.6.

Does anyone have any ideas where this problem lies? Any suggestions, ideas, thoughts, opinions, answers from Magic 8 Balls are all greatly appreciated.

On another note, the initial rattling that I thought was a heat shield is the catalyst breaking up in the convertor. I will address that in a separate post; I just wanted to update everyone as I am sure you were all waiting with baited breath!

Thanks, again! Have a great evening!


Respectfully,

George D.

 

[Mooseman]

What are the voltages reported by Torque and/or an actual multi-meter? The gauge can be misleading at times.

 

[GeoGoGo]

Hey Moose!

The voltages are taken from Torque as I don't trust the gauges at all, Thank you, Mooseman!

 

[Mooseman]

Hmmm. Maybe that external voltage thingy is acting up (I don't know its name. It's like a voltage regulator but not). It's on the battery wire. if you unplug it, the internal voltage regulator kicks in and usually just pumps out full voltage.

 

[budwich]

yes as I suggested earlier, unplug the SAVRC module connector. This causes the alternator to output "standard" voltage of ~13.6v. If it doesn't, you likely have an alternator. If it does, then you might look at replacing the SAVRC module / ground wiring.

 

[kickass audio]

There is a fusible link between the alternator and battery. Highly unlikely to burned it out but it's worth a look into with a multimeter to test resistance of the charge wire coming off your alternator. Also just to make sure you don't have someone elses old junk from the parts store check the alternator yourself. I had one that the bearings spit out the back and the whole pulley would wobble up and down by hand when I removed the belt.

I'd take some resistance measurements from the output stud of the alternator to the + battery terminal as well as from the casing on the alternator to the - battery terminal.

While you're checking the resistance of the output wire on the alternator try to wiggle it around and see if it makes the reading jump around. If it does your wire is probably broken or maybe the terminal is not crimped properly and is coming loose. That can cause erratic behavior like you're seeing.

Finally, try to wiggle the turn on connector that goes to the alternator. If you move that does the voltage go up and down at all? Possibly some corrosion or a loose spade connection on it?

 

[GeoGoGo]

Bud,

Is the SAVRC the module that is molded into the negative cable, right up against the battery? So I would unplug that connector that plugs into the side of the alternator? Just trying to get my bearings here.

I am very surprised that I have not run into any issues starting the truck. Albeit, it has not been very cold since this issue started but I would think after several months running with the alternator putting out 11.5 volts, the battery would die. Is my logic incorrect?

Thank you all again! It is greatly appreciated!

 

[Mooseman]

That would be it. My 07 has it and noticed that it keeps voltages lower than what my 02 did. If you unplug that module, not the one going into the alternator, the voltage should jump up.

Although lower than my 02, mine doesn't go to 11.5v.

 

[GeoGoGo]

Awesome. Thanks guys! Looks like I have something to do after work!

 

[Ilikemy3s]

Any updates ?