Howdy!

I have an issue with my 7.3 2001 Ex front AC Blower. it has two speeds, low and warp 9... I have changed the blower motor relay out twice (one junk yard and one new) and tried two different junk yard switches with no avail... Am I missing anything, or do i change the blower motor next?

 

Sounds like the blower is working just fine.
The blower would normally run at high speed without the speed limiting resistors.
Are your controls mechanical or electronic?
You'll probably need to troubleshoot the speed control circuit next.
Here's some info on typical control circuits - Blower motor resistor: how it works, symptoms, problems

 

98% probability is that it's the resistor pack. It almost always is the resistor when a manual system is installed (EATC doesn't appear to have been available on the 01 Exc) and the blower only works on high speed. It's so common it's included in the FAQs I wrote back in 2009. See link below.

 

Sorry about the lack of detail... yes.. it is the manual AC controls, and i have changed the resister pack twice now (one used, one new) and the wiring harness looks ok.. What else could it be?

 

Make sure there are no lose pins in the back of the plug to the resistor.

 

Clarify the symptom: High-speed only, no other speeds work? That's a resistor pack (or its connector) problem.

There are only THREE possibilities for a loss of fan speeds: 1) See above 2) Defective fan speed switch, or 3) Defective connector at one of the above or a wiring harness fault in between those components.

The blower motor cannot cause this set of symptoms.

A defective switch or its connector is what is usually behind the loss of one or two out of the four speeds. Have you pulled the connector off the fan speed switch and examined it for heat damage?

 

Here's the thing, A bad blower motor can cause other problems. What's a bad blower motor? It's one where the bearings/bushings have worn out. What does that do? It causes more friction on the motor to work harder to spin. How does the motor work harder? Well at lower RPM and constant voltage, the blowers resistance is lower and will pull more current. This should first cause the thermally protected fuse link in the blower resistor to blow and thus the blower resister needs replacing.

Next, as the motor is trying to spin and consuming more current the resistors run hotter and the wiring connectors get hotter because the blower is passing more current. Thus ,as had been said elsewhere, the weakness of the wiring connectors and plugs is the time developed corrosion that creates more resistance that heats connectors and plugs contacts. The hotter the contacts the more oxidation buildup on the contacts causing more resistance in the contacts that create more heat until the connection opens and stops passing current.

The faster the motor spins, the higher the motor resistance. If you could measure the current easily, there is a current table for the different motor speeds in the ford service manual.

Now, here's another problem I'm working on right now. I need a replacement resistor. But it's hard to find one locally for my model and year. But, while they all look the same there is no reference to the difference between model years. How much of a difference is there between similar looking resistors in 1990 and 2000? the connector looks identical.

For my diagnostics, I checked the voltage at the relay up front first, verify the relay worked. It was good. Then voltage to the fan motor. No voltage. Is there a fusible link? I tapped the wires directly with the pen test light point screwdriver which cuts into the insulation well. I thought the relay but just verified it was working. That lead me to the connector. The connector plug wires for the blower motor were fried. Cause, the blower motor bearings/bushings were shot. I was able to bypass and power the blower motor and found it to make a horrible noise. Motor good but bushings shot. I also at this moment checked the resistor and found that open before pulling it out. The test light should light up the connection to the motor if the resistor pack is working and you have the test light wired to 12v. to verify this the light lit up when fan switch was on high.