I turned on my heat this morning and, as usually, it was really loud. It makes a rattling whenever it's on and it doesn't blow very much even on high. Finally this morning it almost completely stopped blowing and it got even louder, but get this, it only happened under 45 mph. When I'm slowing down it gets louder and louder and even makes the whole truck vibrate. When it did this I turned it off until I started accelerating again, and sure enough it went back to "normal" around 50 mph. This is rather odd to me considering it only does this under 45, and it is especially loud and shaky at a dead stop. It sounds like exhaust drone with Flowmaster 40s. I dunno if you've heard them on these beasts, but they drone like CRAZY inside the cab.

Should I just replace the blower motor or could it be something else?

 

Have you checked to make sure there isn't debris caught in the blower motor wheel causing it to be unbalanced and restricting the airflow?
That would be the first thing I would check before ordering anything.

 

I have not, and in fact I don't know how. I'm sure I can find another post with a write up, however.

If it's been like that for a long time is it possible it has damaged the blower?

Even if it's dead, I won't need to order one. I have a whole parts truck and the one in it is probably good.

 

Mine was full of old insulation.

 

Here are the set of instructions which I used last year to clean out the debris:

Australian Land Rover Owners

 

Sweet, I'll get to hopping on it in the next couple days hopefully.

 

My blower has that same vibrating sound/feeling. The vibes/droning sound surfaced out of the blue; ironically it didn't vibrate at all over the summer.

It's worth mentioning that my alternator took a crap. Maybe, the deficient power output is levying a power strain on the blower motor? You mentioned your vibrations disappear when you increase engine speed...Hmm? How's your alternator output?

My new Bosch alternator arrives Wednesday I guess I'll find out then if my theory holds water or if end up having to call Paul Grant for a blower motor.

 

Looks like I got to it quicker than the next couple days; I tore it apart, cleaned out a ton of leaves, and oiled the motor. Seems to be working great now!