Hey guys, so that 2004 FX4 I've got is at it again /sigh.

The blower motor randomly stopped working the other day ago while my wife was driving. I checked what I believe to be the right fuses (113 IIRC and a few others), relays (06) and other basic tests. I haven't checked the power going to the blower just yet but will if I can get it into a garage.

Any advice would be helpful, the heat was already crap in the truck due to a sticking thermostat that needs replacing too. We are somewhat lucky in that we don't have -30*F temps right now and are closer to 20*F..... so we can manage. She is unfortunately driving around with the kids in the truck too, so I want to get this fixed before it becomes a safety issue once it gets colder.

The blower doesn't work on any level and I can hear the blend door and other things switching from the panel when I change them on the console. This is not the climate control, just turn *****. Is it possible for the resistor to be bad and have it not blow on any setting. The typical failure mode is to have the speed only work on full speed if the resistor is blown from what I've seen.

 

No.

See attachment for schematic. Check fuses F13 & F116 in the under dash fuse box. Check for power from the relay at the blower motor terminal 1. If present, check for voltage at terminal 2. If terminal 2 is zero volts, check continuity between terminal 2 and ground. If good, replace the blower motor.

 

Thanks for the schematic ProjectSHO, I tested and it was good. Went to AutoZone and picked up a replacement and fired right up. I didn't realize how "easy" it was to remove and replace the blower motor. Tested the old one in store also with a 12v battery and it was shot. Surprised as it is a Seimen's brand, which generally aren't cheap or junk.

Wasn't sure if the resistor can fail in such a magnificent manner that all power does not pass on to the blower? I'm guessing if so that it would be rare. But good to know generally that isn't a thing for future reference.

Family and I are just happy to have it working again. Again, thanks for the info.

 

It would be so rare as to be impossible, as high speed bypasses the resistor completely (see schematic).

Happy to help, glad it worked out!

 

Thanks for letting us know what the problem was. projectSHO89 is one of the most knowledgeable forum members!!!