Alright guys, I'm on my second blower motor and fourth blower motor resistor since purchasing my 2000 Ex approximately 3 months ago. The fan returns after replacing the resistor but ultimately, fails after 2-3 weeks. What can I test, what can I do? I'm handy enough to build a kit car and this is kicking my butt. If anybody has any other threads where this problem was solved, and/or recommendations for other parts which may cause it to fail, I'm extremely grateful. The weather is changing quickly here in NOVA and being without a reliable heater is a non-starter for the family vehicle.

 

If the resistor is getting somehow wet its going to keep braking check for leaks.

 

So in all the rain we have had I opened the hood and it is bone dry. There's a few drops of water coming from under the fan and a few under the resistor as well. What gives? Where is the water getting in? We are hoping for a break in weather today but if anybody knows where the clog may be before I start throwing time and money at it, I am grateful.

 

Only way to know for sure is to inspect windshield and possibly pull some/or all of the dash out to look for water damage/penetration. Dash is not that hard to get out. You can also drop the glove box easily for access to some things under there. I agree with z31 that you have a short somewhere, possibly caused by water intrusion if you found water dripping. Possibly a windshield seal problem. The resistor is positioned in a place where it is susceptible to moisture anyway (next to the evaporator). They are usually a bit rusty/corroded after a few years.

 

Assuming a manual climate control system....

You probably do not have a short circuit as there isn't one possible that will take out either the blower motor or the resistor.

Before tearing anything apart, it's time to do some evaluation.

What was the specific failure mode for each of the resistors and the motors?

What does that actually mean? The ONLY thing the resistor does is to provide the three lowest speeds. It isn't even in the circuit for HIGH speed, you can unplug the resistor completely and high speed will not change.

When you had the blower out, did you check for airflow restrictions in the evaporator core or for any foreign materials (insulation, critter nests, plastic wrappers or bags, etc?

Have you inspected the blower speed control switch and its connectors?

 

Check for a bad ground. The extra resistance can cause excessive heat, burning out the resistor and eventually the motor.

 

Thanks for the input guys. I pulled the black cowling below the windshield off and inspected the drains there. All looked good, but the intake bow for the fan had standing water around the part I could see. Everything looked okay but as I'm the third owner and there was a significant amount of dead foliage under the passenger side cowling, I think it's probably been taking in water for some time. Pulling the fan and actually looking for the problem, I discovered what was likely a quart or more of standing water in the air intake box. I can only imagine what the spinning wheel was working against, not to mention it was working harder to throw the water into the resistor.

Solution. Without drilling or cutting new holes, the I fresh air intake CANNOT be accessed to reseal it. Caulk would have done the job but Ford blocked off the passenger side with only a small inspection hole. With my dremel I put two 1/8" holes in the bottom of the box and it won't hold a drop now. Not the ideal solution but there isn't a filter on it anyway, and it's a 15 Y/O truck. I'll post if the problem returns but I suspect it won't.

To the first response, thanks for pointing that out. I would not have looked for the seeping in the middle of a storm and can only imagine how much longer I would have chased this.

 

For future reference-

The only ground involved here is the one on the passenger side, just forward of the plug for the cruise servo (right near the vacuum hub solenoid if you have a 4x4). That ground supplies the blower resistor, cruise servo, the under-hood AC sub-harness, the horn, and all passenger side front lights.