Blower Motor Problems - Testing/diagnosis

[Greg]

So, my blower motor stopped working. I can hear the BCM clicking when turning the fan off and on. Tried hitting the BCM - no luck.

Removed connector from fan. If I hook a ground up to the connector for the Brown/red stripe and then positive to the Red/White stripe the blower works.

I can even connect the Red/white stripe wire to the motor and leave the ground connected separately and the motor works but no speed control.

So, is it the BCM because the ground side is not connected and that is the side that controls the speed? In other words variable resistance from the controller?

Please help

[BAD MERC]

I believe the motor has hot 12 volts all the time and ground is varied. Sounds like the module behind the passenger cam cover, right under the heater core hoses.

[Turbov6Bryan]

Yes, good diagnosis. Blower motor works then the BCM has failed and on yours it is not the high speed relay that normally fails.

I would try and get a ford product.... dorman is crap.

That harness that plugs to the BCM is about 2 foot long after its unplugged, no need to actually remove the BCM if you wanted to test the new part to fix it.
I actually burn thru a few of these on my cars, it is what it is.
And one car the BCM is strapped to the large AC line to test the other ones i have.

Good luck

[fastblackmerc]

Probably the BCM.

[Greg]

Time for a BCM .....

[Mackdombles]

Did you test the resistor pack on the firewall? Maybe I missed that

[fastblackmerc]

Did you test the resistor pack on the firewall? Maybe I missed that

Huh? Resistor pack?

[Mackdombles]

So, my blower motor stopped working. I can hear the BCM clicking when turning the fan off and on. Tried hitting the BCM - no luck.

Removed connector from fan. If I hook a ground up to the connector for the Brown/red stripe and then positive to the Red/White stripe the blower works.

I can even connect the Red/white stripe wire to the motor and leave the ground connected separately and the motor works but no speed control.

So, is it the BCM because the ground side is not connected and that is the side that controls the speed? In other words variable resistance from the controller?

Please help

First,
Turn on the key and the blower control to high.
Then go out and check with a multi meter if the motor has at least 12v to the power wire, and make sure the ground wire has a good ground with little to no resistance to battery ground. If it is missing power, check blower fuse first then wiring. If it has no ground, locate the resistor pack behind the pass head on firewall.
The orange/red stripe wire is the control wire. It will vary in resistance to ground as you change settings on the unit.
If it has an open connection and doesn't supply ground at any setting, check the
Light blue/orange stripe wire. It comes from the hvac system and is the wire that tells the module how much ground to give the motor. It should also vary as you change settings. If it does have signal and varies, it is a bad resistor module.
If It doesn't vary, check the eatc module.
This is a closed system and doesn't run through the bcm.

[Mackdombles]

Huh? Resistor pack?

Yes sir the blower motor resistor pack behind the pass head?
Ford calls it the blower motor speed controller

[Mackdombles]

Bwd part number ru1097 without auto temp and part number ru572 with auto temp.

[Mackdombles]

Fuse 103 is the 40 amp blower fuse. Engine bay fusebox

[Mackdombles]

Or are you guys calling that a BCM.
Acronyms will get you if you go to ford and order a BCM. You will get a body control module. My apologies if this is the module you guys are referring to as a bcm

[Agent2006]

blower resistor is another term. Greg PM me if you need a scan of the wiring diagram for that circuit

[Greg]

I don’t seem to have any ground on the orang/red stripe wire. The fuse is ok.

[Mackdombles]

OK. The etac tells the little resistor module how much ground to show the motor. This is what varies speed. High is a straight ground connection and is activated completely separate from the other speeds. It even has its own wire for input from the eatc. If high doesn't work as well as the other speeds, and you have power at the motor, it almost always is not the resistor pack as even when the business end of the resistor pack goes bad, it only effects low and medium speeds. High should still work.

[Turbov6Bryan]

you can buy a cheapy one at autozone and try it out... like i said the harness is 2 foot long. Just to test it and say you never used it and buy a ford part.

The bcm is common to fail.

As Macdombles said, there is a manual controller bcm and a digital display controller bcm... Order the digital display one (obviously)

Actually having the new BCM in hand will help you figure out how to unplug the sucker, its awkward back there.
Hope your not a lefty.

[Mackdombles]

This module is kind of hard to get to. And if you do buy a module that you plan to use and keep, please do not test the blower speeds for very long with the module out as the reason it is mounted where it is, is because they are resistors, they get very hot. There in the blower ducting to cool them as they work. They go bad often so it's obvious they barely keep cool enough to make it out of warranty. If you use any speeds other than high you will smoke this module in seconds not to mention it will burn you if you hold it while it's on.
And if you do buy a cheap one to take back after you test it, keep in mind the next guy will have either a bad, or severely damaged new out of the box.

[PHHHHTT]

FWIW,
I have over 16 years experience (part time positions) in auto parts sales. Please keep in mind, most parts stores will inform you that if you buy an electrical part and connect it, whether it is a battery or a switch, the part is yours. If it is an item that carries a warranty, I will warranty it out with a new part but the store will not give you cash back on an obviously installed item. Most parts men (or ladies) will examine the contacts for scratches that indicate the part has been connected.
Don't mean to dampen anyone's attempts to repair their vehicle, but don't be surprised if you encounter resistance to return an obviously installed electrical part.

[Joe Walsh]

Not to derail the thread....but resistance/heat sink 'technology' is still being used to control electric motor speeds....???
I think that Edison invented it 100 years ago!

Hasn't any OEM heard of PWM for motor control?

[Mackdombles]

I feel the same way about thermostats

[Turbov6Bryan]

I've had my BCM strapped to the main ac line for 2 years and it's not smoked..

I assume ours IS pwm

[Mackdombles]

I've had my BCM strapped to the main ac line for 2 years and it's not smoked..

I assume ours IS pwm
The auto climate ones aren't the old resistor ones. They don't produce the heat as the others.
Id like to see a brushless motor with a 40 amp esc from the rc world. It would be an easy swap!

[RF Overlord]

Just to be pedantic, because my father was an English teacher, it's not a resistor. I know, I know...a lot of the parts books and sites call it that, but just because they're ignorant, there's no reason we have to be.

It's called a BMSC- Blower Motor Speed Controller module. It works by creating a PWM (Pulse-Width Modulation) signal just like a high-end model train controller, which switches the ground side of the circuit. The EATC sends a signal of 1 to 2 volts to the BMSC which translates that to variable speeds of the blower motor. There is also a relay that bypasses the PWM circuit and connects the blower motor directly to ground, to produce the highest speed.

The resistor pack which is used with manual HVAC controls is exactly that...a circuit with 3 small coils of resistance wire, like in a toaster, that are switched in various combinations to lower the voltage at the blower motor. The high position just bypasses all the coils.

[MyBlackBeasts]

Just to be pedantic, because my father was an English teacher, it's not a resistor. I know, I know...a lot of the parts books and sites call it that, but just because they're ignorant, there's no reason we have to be.

It's called a BMSC- Blower Motor Speed Controller module. It works by creating a PWM (Pulse-Width Modulation) signal just like a high-end model train controller, which switches the ground side of the circuit. The EATC sends a signal of 1 to 2 volts to the BMSC which translates that to variable speeds of the blower motor. There is also a relay that bypasses the PWM circuit and connects the blower motor directly to ground, to produce the highest speed.

The resistor pack which is used with manual HVAC controls is exactly that...a circuit with 3 small coils of resistance wire, like in a toaster, that are switched in various combinations to lower the voltage at the blower motor. The high position just bypasses all the coils.


Yep. Spot on with that info. Couldn't count the number of those old BSC units I've replaced in a couple past lives.

[Turbov6Bryan]

Yep. Spot on with that info. Couldn't count the number of those old BSC units I've replaced in a couple past lives.

What's even funnier is when you're 15 years old and you don't know how that stuff works and you wonder why your fan speed doesn't work so you take the resister pack out and you grab the wires that were just being used and you touch the coil and burned the ever living **** out of your fingers. I may know somebody that did that.

[MyBlackBeasts]

What's even funnier is when you're 15 years old and you don't know how that stuff works and you wonder why your fan speed doesn't work so you take the resister pack out and you grab the wires that were just being used and you touch the coil and burned the ever living **** out of your fingers. I may know somebody that did that.




:rofl::rofl::rofl::rofl::rofl:


Yes, we all have those learning experiences.


It's OK too, if you learn from it but if you do it a 2nd time, well then...

[justbob]

I’ll try just about anything three times.



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[MyBlackBeasts]

I’ll try just about anything three times.



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:lol: Well if you did this 3 times it would have to be the masochist in you coming out!

[Greg]

Update: It was the Blower Control Module

What a pain in the butt to get out. dropped one of the screws and still haven't found it.

Had to take off the heater core hoses.

Another Note: The heat shielding on the blower box was disintegrated. I bought some of the stick on heat shield from Advanced Auto. Will try to get that on there tomorrow.

[justbob]

Update: It was the Blower Control Module

What a pain in the but to get out. dropped one of the screes and still haven'y found it.

Had to take off the heater core hoses.

Another Note: The heat shielding on the blower box was is disintegrated. I bout some of the stick on heat shield from Advanced Auto. Will try to get that on there tomorrow.



I removed all of mine years ago and it still freezes me out of the car.


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