Low sounding whine that gets louder with the headlights on

I started hearing a low sounding whine coming from the front. When I turn the headlights on it gets louder. Alternator?

 

Engine on? AC on or off?

 

Engine on, as off.

 

Ac off. When I turn the headlights on the noise gets louder.

 

So it’s doing it with the engine on and off? That would not be the alternator sounds more like it could be a relay not fully engaging causing a buzz. Find the relay for the headlights and see if that’s the location of the noise. If so replace it.

 

Sometimes no noise at all, other times loud as hell

 

No, only when the truck is on. There is no buzzing sound its a very low whining sound.

 

Low as in deep hum sound

 

Pop the hood and try to find the noise. Can’t help much more without being there.

 

First impression is belt and alternator. When electrical load is introduced, the alternator works harder and also creates more drag/resistance on the belt. If example, if your widows are up and you hit the up button again, the motors draw and sometimes your idle will get lower. Diagnosing "noise" in a forum is a little tricky haha. I would start with checking the belt and alternator first and go from there. If the belt is old, it wouldn't hurt to replace it but a deep hum would suggest to me a bearing etc. issue in the Alt. Does the hum sound change with engine RPM?

 

Ha! Just got back from buying belts yes the belt was worn an yes it does change the sound goes away. So I'm looking at the gen. I have to go threw two belts just to take that one off I'm thinking just go ahead and replace all the belts?

 

Wouldn't hurt to replace them all if you are already there. Keep the old ones for emergency in the car somewhere. With the sound going away with RPM, we know can assume it is related to rotation. Once the belt is off, wiggle the Alt pulley and see if there is any movement. Because it is a "hum" vs a "squeal" I am still leaning to bearings or brushes in Alternator. Also, when the belts are off, check the tensioner for play as well. I am not thinking the tensioner is making the noise but since you are already there, it would be worth changing if it is worn. Let us know what you find.

 

Yes I will and so much for the info.