How can I tell if my front ac blower is out or the resistor is out? Back works fine.

The fan was coming on sometimes and stopping. Now it will not come on at all.

I am getting prices on replacement and its like $500 for something I can do in my yard in ten min.

I just dont know how to tell which part to buy.

I have attached a picture of the plug that plugs into my blower motor. It has black marks on it. What does that mean?

2009 Expedition EB 4x4

Side note. Sometimes when AC does run I get a smell that smells like a new float. You know the smell. Like you are going to the lake and oh **** you forgot your float you stop buy a new one and it has that smell.

 

Usually,,,,,,,,,, if the resistor is out to lunch you will still get hi speed.
If the blower motor itself has gone into retirement, you get nothing anytime + if it has been overheating due to excessive current flow, that generates heat and the baking begins. Everybody's perception of "smell" is different and , well anyway , sometimes it fries itself or components,
or if bad enough will cause the fuse to open.

If the motor was pulling excessive current thru the resistor it can cook that part also.

 

I was worried there!! ,, if it smells like burning tennis shoes much more of a concern
Hard to tell on the blower connector, but looks more dirty, than baked..

Auto temp control will have the blower control module, manual temp control will have the blower resistor. The common failure like Hanky mentioned (when equipped with a resistor) is the thermal protector (looks like a diode) across the heat piles goes open, and the dead give away is the fan only works on high mode. So,, with EATC, a blower module and of course the HVAC module. The blower itself can easily be proven just adding in fuse protected voltage for motor run.