DavidEBSmith
Elite Explorer
- Joined
- January 26, 2004
- Messages
- 112
- Reaction score
- 2
- City, State
- Chicago, IL
- Year, Model & Trim Level
- '07 Mountaineer Premier
So, on my 96 Limited, the EATC blower motor speed controller module went out. We lived with the blower fan only working on high for several months. Then it started working again. Then one morning the truck was dead, the battery was dead, and when I hooked up the battery charger, the blower fan came on, even though the ignition was turned off. 
I disconnected the battery, charged it up, and when I reconnected it after a few hours, the blower fan stayed off. My suspicion was that the flaky blower motor speed controller module was the problem, so of course I put off doing anything about it for a couple weeks. Then the truck was dead again.
So I got a new blower motor speed controller module, which comes with a new connector that you have to splice onto the existing wiring. And of course, all 5 of the wires on the connector are white. So I got out my Ford Technical Services Publications CD I got offa eBay to look at the wiring diagram.
According to the CD, the blower motor speed controller module shouldn't be able to turn on the blower fan with the ignition off. The wiring diagram says that power comes from the power distribution box, is switched by a blower motor relay that is controlled by the ignition switch (on in Run), to the blower motor, to the EATC blower motor speed controller, to ground. So there should not be any power to the blower motor with the ignition off.
The blower motor relay is supposed to be in auxiliary relay box #2. Also in there are supposed to be the fog light relay and the windshield washer pump relay, for a total of 3 relays. In auxiliary relay box #2, I have two relays, not 3. Neither was stuck on, and both turn on and off as they're supposed to.
So with the key off, the blower motor relay should not be turned on, and apparently is not turned on. There should be no circuit path from +12 to the blower motor to the blower motor speed controller module (and thence to ground to complete the circuit). So when I pulled the controller module, I checked the wire from the blower motor that should have no power to it. It did. According to the wiring diagram, this is impossible. (However, it would explain why the bad blower motor speed controller module could let the blower fan run with the ignition off).
So my question is, does anybody know how this is really wired? I'm thinking that with EATC, there really is no blower motor relay, that power runs from the power distribution box, to the blower motor, to the blower motor speed controller module, which switches the blower motor on and off at various speeds. This would explain why the auxiliary relay box # 2 is short one relay, and why the blower fan would run with the ignition off and drain the battery (with the bad speed controller in place). It would also mean that the wiring diagram is wrong. Anybody know?
I disconnected the battery, charged it up, and when I reconnected it after a few hours, the blower fan stayed off. My suspicion was that the flaky blower motor speed controller module was the problem, so of course I put off doing anything about it for a couple weeks. Then the truck was dead again.So I got a new blower motor speed controller module, which comes with a new connector that you have to splice onto the existing wiring. And of course, all 5 of the wires on the connector are white. So I got out my Ford Technical Services Publications CD I got offa eBay to look at the wiring diagram.
According to the CD, the blower motor speed controller module shouldn't be able to turn on the blower fan with the ignition off. The wiring diagram says that power comes from the power distribution box, is switched by a blower motor relay that is controlled by the ignition switch (on in Run), to the blower motor, to the EATC blower motor speed controller, to ground. So there should not be any power to the blower motor with the ignition off.
The blower motor relay is supposed to be in auxiliary relay box #2. Also in there are supposed to be the fog light relay and the windshield washer pump relay, for a total of 3 relays. In auxiliary relay box #2, I have two relays, not 3. Neither was stuck on, and both turn on and off as they're supposed to.
So with the key off, the blower motor relay should not be turned on, and apparently is not turned on. There should be no circuit path from +12 to the blower motor to the blower motor speed controller module (and thence to ground to complete the circuit). So when I pulled the controller module, I checked the wire from the blower motor that should have no power to it. It did. According to the wiring diagram, this is impossible. (However, it would explain why the bad blower motor speed controller module could let the blower fan run with the ignition off).
So my question is, does anybody know how this is really wired? I'm thinking that with EATC, there really is no blower motor relay, that power runs from the power distribution box, to the blower motor, to the blower motor speed controller module, which switches the blower motor on and off at various speeds. This would explain why the auxiliary relay box # 2 is short one relay, and why the blower fan would run with the ignition off and drain the battery (with the bad speed controller in place). It would also mean that the wiring diagram is wrong. Anybody know?
