I'm on my second mo. of ownership in this used truck. It has developed a loud whining noise coming from the front of the engine when it becomes warm. The belt is dry and cracked and needs replacing.

Lately when starting, the alternator gauge stays below 14 volts until the engine speed increases.

My question concerns the belt first. When they're ready to be changed, do they make noise? Secondly, could the alternator be on it's way out and making the noise?

 

Could be grid heaters drawing it down, but if it is whining sounds like bearings are going out.

 

They are usually pretty durable alternators, but a shorted diode can also cause a whine noise. You can diagnose this by disconnecting the field circuit from the alternator while it is whining. As soon as the alternator stops working, the noise will go away.

 

I'm having the same whine, low volt reading on the guage and the "Check Guages" warning at idle.

I had to drive 140 miles yesterday, truck was fine most of the trip at highway speeds, but it didn't seem to be running as it should. It almost didn't start once after some stop and go driving in town.

I have almost new batteries, cleaned the terminals a few months ago. But I don't remember if I cleaned the crossover battery wire terminals at the time. Belt is tight and doesn't seem to be slipping.

My Smarty read a DTC code P1682 - Charging system voltage too low.

I'm not working right now, money is tight and the wife's car is snowed in and I need the truck to get her to work tomorrow. I just want to be sure before I buy an alternator today. Auto Zone will have it in at 3PM.

Anything else I can check? Or do you guys agree, it's the alternator?

Thank you.

 

Just check the alternator. Find a cheap multimeter. A good charing alternator should be around 14V DC.
or take it off and have autozone/napa/parts store test it.

How much is Autozone getting for an alternator?

 

when testing an alternator, you want an amp clamp, as well as a voltmeter.

Check for voltage present, between 13.9 and 14.5

Amperage output should be checked with all accessories on, and if possible, while the grid heaters are cycling, this will show you the MAX output of the alternator, as the grids cycle.

Otherwise, Amp testing is best done with your amp clamp on the output cable of the alternator, and a load tester hooked to the batteries. Draw the battery voltage down by exactly 1 volt. this will make the alternator charge as hard as it is ever going to.

Good luck

 

Thanks a bunch guys.

I checked it and Auto Zone checked it and we both agreed, it wasn't charging.

I changed it right there in the AZ parking lot. Had it off in about 5 minutes and the new one on in about the same time. But I decided to change that **** serpentine belt while I was in there. Never changed one and the sticker that shows how it goes was gone...that thing kicked my butt. It took about 20 minutes to figure it out.

Their price was $186 for the alternator and $32 for the belt.

 

I'm headed to Autozone in the next couple days to do the same. I tried unsuccessfully to isolate the noise, but it is coming from the front of the engine.

I'll replace the belt, it needs it, and the alternator if it shows bad. One other option if either of those two changes don't eliminate the noise would be to check the bearing in the belt tensioner I suppose. That should be easy enough to check while the belt is off.