Buzzing noise, increases with RPM when fan on

I've had an increasing buzzing/humming/whirling noise the past few weeks. The sound/frequency increases with the RPM and drops to almost nothing when I depress the clutch.

The sound is only there when the blower fan is on. Turning the AC on or off does not affect it.

I can't pinpoint where the sound is coming from. It's more less from the center vents, but could be the glovebox area.

I'm thinking it's the blower fan, but would that be affected by RPM? I'm planning on getting the alternator tested, but is there anything else I should check?

Around the time the noise started I had a little trouble starting it now and then. I would just get a loud clicking for a couple seconds before the engine would start to turn over, then it'd start up fine. This was more likely to occur when the truck had been driven recently, never for the first start in the morning. The clock also reset itself once during this time.

There has been a record amount of rain this month as well, so water could have gotten somewhere that it normally doesn't.

I've got a '95 V6 5MT 4x4, ~260k miles.

Thanks for any insight.

 

Possibly an alternator failing or bad connection at your battery, have you checked charging voltage?

 

this sounds like a grounding issue to me. There is one strap on the back of the P/S cylinder head that goes to the firewall, a second that goes from the negative battery cable to the inner D/S fender and the large one from the negative battery cable to the engine block. The cable ends could be corroded, the wires frayed or acid has crept into the harness. There are a few posts on this forum related to the replacement of these grounds. If these grounds are not clean and secure the amperage from starting the motor is going to take the path of least resistance... sometimes it is NOT through what you want it to be, like the accelerator cable.

They might be related but then again the noise in the fan could be something as simple a leaf is in the squirrel cage. 3 - 10mm bolts and 5 minutes to R & R the blower motor housing to take a look.

 

Update:

I tested the alternator and it is okay. The battery is going bad though.

For now the noise has gone away, but a new one's started in the wheel well, so my focus is on that for the time being.

 

I would remove and check the blower motor for leaves and such.

Since the problem is intermittent, one thing you could do is disconnect the fan's power connector, preferably just after you've been hearing the noise. Then drive around for a few days and see if the noise returns.