You are correct based off of the information I am looking at. There is a blower motor in the back.
Not knowing your level of mechanic ability is hard to say if you are able or not. I feel, general basic knowledge is okay for this. It seems to be removing the interior trim panels and locating the blower motor.
There may be something hitting the fan or it may have come loose.....the squire cage part
Me, I would first remove the panels and get to it to see what was the matter. It may be something very simply.
If you do have to replace the fan, I have attached two different OEM parts/prices for you. Boy, it had to be the rear............that one is a little more pricy than the front.
I would definitely check auto part stores. But then again, you may get in there and see you don't need anything.
I have also attached a TSB on the subject of hearing noises back there. The noise you describe doesn't look like this, but wanted you to review for yourself.
I have also attached a pic of the blower.
A/C - Rear A/C Hoot/Whistle Noise
HOOT OR WHISTLE NOISE FROM REAR A/C
This article supersedes TSB 05-21-1 to add a production fix date.
Some 2005-2006 Expedition/Navigator vehicles built before 1/30/2006 may exhibit a hoot or whistle noise inside the passenger compartment, coming from the rear auxiliary A/C system. The noise will most likely be heard by the customer when driving the vehicle with the interior cooled down, the rear A/C off, front A/C on, and the blower fan on the low speed setting.
Replace the thermostatic expansion valve (TXV), located near the rear auxiliary A/C housing, following the Workshop Manual procedure (Removal And Installation: Thermostatic Expansion Valve). The procedure can be found in Section 412-03B of the 2005 MY Workshop Manual, or Section 412-02 of the 2006 MY Workshop Manual.
Thursday, December 18th, 2008 AT 2:27 PM