Loud noise from under the hood when HVAC Fan is on

08 Tacoma V6
When I turn the fan speed from Off to any one of the speed settings I am getting a VERY loud medium pitch whine from under the hood. I am using heat not A/C.

This may be related or not, but a few weeks ago I started seeing the A/C light flash. I bought a new A/C relay after reading a few posts here, but haven't gotten around to putting that in yet.

Any suggestions would be much appreciated.

 

Does it do it on Floor, Vent, and Bi-vent (floor+vent)
If you are on Heat and ANY Defrost setting then the A/C is On. Even if you didn’t turn it on.

 

Great question. Ok, just went out and checked. It only makes the noise when the selector is on one of the defrost settings.

 

I’m no A/C guy. @Jimmyh is A/C guy around here.

I just knew the A/C works in defrost.
So, I am going with we’ve narrowed it down to the A/C System.
Leaning further towards a compressor issue. But like I said, I have limited knowledge of the AC System.

 

I would venture to guess that the problem is with the AC Compressor Clutch or the belt slipping. Cross your fingers as they are relatively easy to replace.

That being said it could still be the compressor, but usually when it goes it goes all at once.

Have a look at the A/C Clutch and belt while switching the AC on and off.

The blinking LED only says that the compressor is not turning the correct RPM when the AC is on.