Testing Blower Motor Speed Controller

[ranger2131]

So I have a couple different symptoms. 2006 GM

1) air only works on defrost/floor settings, no air out of vents
2) air only works on highest fan setting- no work on medium to low speeds

For symptom #1 I replaced the solenoid O-rings in EATC head unit. Two of the old ones indeed felt very brittle. However it did not fix the issue.

I decided to move on to symptom #2, hoping that perhaps a bad BMSC was not only messing up the fan speed but also somehow triggering the "emergency mode" and causing symptom #1. It's probably impossible but a guy can hope right? Besides I figured one problem at a time and I already did the most common fix for EATC (got lots of hiss when the vacuum hose cluster was removed from back of unit, fwiw)

Anyway I (finally!) got the old blower motor speed controller out of there. I removed it from it's case out of curiosity and can find no obvious visual flaws. I compared it to pics on this site of some known bad ones, and there is nothing that looks amiss with any solder points. So I was hoping that someone could please tell me a way to test this thing with a multimeter before I go buying a new one? I see 2 large pins (I assume power and ground?) and 3 small pins. Could someone please walk me through measuring the resistance on this thing? Which contacts to touch and what expected resistance values should be? Any help here would be greatly appreciated- speak to me like I'm a 5 yr old would be great ;)


At this point I'm sorta wondering if my EATC head is just bad and causing all the symptoms itself. I figure if the BMSC bench tested ok, along with the o-ring "fix" not doing anythign, then that would be two points to confirm this suspicion of a bad EATC head unit. A new BMSC isn't too costly, but I'd hate to buy one and then discover the old one was fine and wish I could have just put that money into a new EATC head unit.

Also if the BMSC is indeed bad and needs replacing, should I go ahead and replace the blower motor as well despite the fact the old one obviously works? Thanks for any help!

[BLACKMARAUDER04]

Did you run a diagnostics on the EATC unit?
Could be your blend door actuator.

[RF Overlord]

Could be your blend door actuator.Once again: the blend door only controls the temperature of the air, not the amount or direction of flow.

[fastblackmerc]

Once again: the blend door only controls the temperature of the air, not the amount or direction of flow.

I don't know why most people don't get that...

[fastblackmerc]

So I have a couple different symptoms. 2006 GM

1) air only works on defrost/floor settings, no air out of vents
2) air only works on highest fan setting- no work on medium to low speeds

For symptom #1 I replaced the solenoid O-rings in EATC head unit. Two of the old ones indeed felt very brittle. However it did not fix the issue.

I decided to move on to symptom #2, hoping that perhaps a bad BMSC was not only messing up the fan speed but also somehow triggering the "emergency mode" and causing symptom #1. It's probably impossible but a guy can hope right? Besides I figured one problem at a time and I already did the most common fix for EATC (got lots of hiss when the vacuum hose cluster was removed from back of unit, fwiw)

Anyway I (finally!) got the old blower motor speed controller out of there. I removed it from it's case out of curiosity and can find no obvious visual flaws. I compared it to pics on this site of some known bad ones, and there is nothing that looks amiss with any solder points. So I was hoping that someone could please tell me a way to test this thing with a multimeter before I go buying a new one? I see 2 large pins (I assume power and ground?) and 3 small pins. Could someone please walk me through measuring the resistance on this thing? Which contacts to touch and what expected resistance values should be? Any help here would be greatly appreciated- speak to me like I'm a 5 yr old would be great ;)


At this point I'm sorta wondering if my EATC head is just bad and causing all the symptoms itself. I figure if the BMSC bench tested ok, along with the o-ring "fix" not doing anythign, then that would be two points to confirm this suspicion of a bad EATC head unit. A new BMSC isn't too costly, but I'd hate to buy one and then discover the old one was fine and wish I could have just put that money into a new EATC head unit.

Also if the BMSC is indeed bad and needs replacing, should I go ahead and replace the blower motor as well despite the fact the old one obviously works? Thanks for any help!

BMC will not have any affect on the vents.

Vacuum or the lack of will affect the vents.

Did you make sure the o-rings were the proper size, installed correctly with a small amount of silicone dielectric grease, the springs were put back, the pistons are installed in the correct orientation?

Is the red connector from the solenoid panel positioned on the system board connector the right way?

Do you have vacuum at the black hose at the rear of the EATC?

Sometimes the bad solder joints on the BCM are hard to see.

You could have a bad EATC, although it's highly unlikely there are two things wrong with it.

[captain]

Can we ever add to a solution without the.. "once again" or the "why don't you get it" ??
Or the ever useless comment.. "Search is your friend".??
Whats up with that? That has always bugged me about this place. Part of why I don't play here anymore. Kinda takes the fun out of participation. to get your face slapped every time you log on.
Wait for it....Here it comes....

[ranger2131]

BMC will not have any affect on the vents.

Vacuum or the lack of will affect the vents.

Did you make sure the o-rings were the proper size, installed correctly with a small amount of silicone dielectric grease, the springs were put back, the pistons are installed in the correct orientation?

Is the red connector from the solenoid panel positioned on the system board connector the right way?

Do you have vacuum at the black hose at the rear of the EATC?

Sometimes the bad solder joints on the BCM are hard to see.

You could have a bad EATC, although it's highly unlikely there are two things wrong with it.

That is precisely why I'm afraid I have a bad EATC. Couldn't a bad EATC cause both of my symptoms on it's own?

And correct me if I'm wrong but otherwise (meaning EATC is ok) then my two symptoms point to most likely both bad O-rings and a bad BMSC.... so two parts failing at once...correct?

I was all excited replacing the O-rings thinking that would solve the blow on defrost/floor only issue, and then I could go straight forward to replacing the BMSC. But since the O-ring fix didn't do anything so far as I can tell, I'm now afraid the replacement BMSC would be a waste of money. Especially since the old one looks great. I mean the entire part and all the solder points look nearly new, there was no corrosion on the connector, etc.

Does anyone know how to test the BMSC with a multimeter for the proper resistance readings? I cant help but think that is my next logical, most simple step, if only I knew what I was looking for :confused: ? If it bench tests out as good, then that, along with the O-ring not solving symptom #1 dilemna, would likely point me to replace the EATC. Correct?

Thanks for yalls expertise

[Badass_forever]

what car/truck are we talking about here. there are A LOT of 2006 gms that have problems.

[RF Overlord]

what car/truck are we talking about here. there are A LOT of 2006 gms that have problems."GM" is understood on most Panther-platform boards to mean Grand Marquis.

[ranger2131]

yes, grand marquis,

fwiw my 2005 "GM" silverado is what I'm driving to the part store for parts for my '06 grand marquis that sits in the driveway (and has already had the blend door problem fixed a couple yrs ago) ;)

[ranger2131]

BMC will not have any affect on the vents.

Vacuum or the lack of will affect the vents.

Did you make sure the o-rings were the proper size, installed correctly with a small amount of silicone dielectric grease, the springs were put back, the pistons are installed in the correct orientation?

Is the red connector from the solenoid panel positioned on the system board connector the right way?

Do you have vacuum at the black hose at the rear of the EATC?

Sometimes the bad solder joints on the BCM are hard to see.

You could have a bad EATC, although it's highly unlikely there are two things wrong with it.

1) Yes, and afaik on the pistons (I couldn't tell much difference but I'm pretty sure I got them in the same way they came out)

2) I think so. Again, I put everything in the same way it came out, afaik. If I didn't, well, I don't know what it's supposed to look like now ;) Besides, everything works the same way (ie. it didn't fix the problem, but the problem is the same and nothing changed with the function)

3) Yes. I don't know if it's strong enough but it feels ok.

[EMAS]

You can't test a blower control module with an ohm meter per se. The ETAC sends a pulse width modulated signal to the BCM in proportion to the speed it is trying to achieve. That in turn varies the duty cycle of the transistor that controls the fan on the less than high setting. Now you could see if the relay that provides high speed it working but since it works on that setting there really isn't a point. If you can find the wiring diagram and have a multimeter than can read frequency then you can test to see if a signal for less than full speed is being sent to it.

[captain]

do those have a self diagnose ? press this... hold that... presto??

[fastblackmerc]

do those have a self diagnose ? press this... hold that... presto??

Yes the EATC does have a self-test feature. Google it.

[RF Overlord]

Can we ever add to a solution without the.. "once again" or the "why don't you get it" ??
Or the ever useless comment.. "Search is your friend".??
Whats up with that? That has always bugged me about this place. Part of why I don't play here anymore. Kinda takes the fun out of participation. to get your face slapped every time you log on.
Wait for it....Here it comes....The issue is that the same faulty information keeps getting propagated here. Telling people it might be their blend door actuator when it cannot be might lead someone to take that advice at face value and waste a lot of time and/or money pursuing it. Replacing the actuator is not a quick or easy job.

[fastblackmerc]

Googled "ford eatc self test"

Youtube videos:

https://www.youtube.com/watch?v=TV6TVDR0TTA

https://www.youtube.com/watch?v=hAqE-oYnvlQ

Written instructions:

http://www.idmsvcs.com/2vmod/eatcswap/selftest.html

http://www.crownvic.net/ubbthreads/ubbthreads.php?ubb=showflat&Number=2357073

Whew!!! that was hard...

Took all of 0.63 seconds to return 6.840 results.....

[GreekGod]

BMC will not have any affect on the vents.
If I recall correctly ...

I found with the two bad BMC's I have replaced, that lack of vent air was exactly what indicated their failures. Both times, the failure mode meant defrost blown air only.

Have I mis-understood your statement?

==

[fastblackmerc]

There are 3 main parts of the HVAC system (the way I see it)

EATC - controls the vacuum motors to direct the air to the floor, defrost etc. It also controls the air temperature by telling the Blend Door Actuator how much to open or close. It tells the A/C compressor to turn on or off and tells the blower motor how fast to turn.

BCM - Think of it like the old time blower motor resistor.

Blend Door Actuator - controls the temperature of the air entering the cabin.

EATC problems - bad o-rings will cause a vacuum leak sending the HVAC system into fail-safe mode - heat and defrost. You can also have a bad circuit board cause the solenoids not to operate so the air doesn't come out the right vents or may case the blower motor not to work or only work on one speed.

BCM problems - bad solder joint causes the blower motor not to work.

Blend Door Actuator problems - Only hot or cold air.

[fastblackmerc]

If I recall correctly ...

I found with the two bad BMC's I have replaced, that lack of vent air was exactly what indicated their failures. Both times, the failure mode meant defrost blown air only.

Have I mis-understood your statement?

==

A bad BMC will not cause air to only come out the defrost vents. It's only function is to control the power sent to the blower motor. My BMC is on it's way out. I have no air coming out the vents but I can hear the vacuum motors operating.

[GreekGod]

A bad BMC will not cause air to only come out the defrost vents. It's only function is to control the power sent to the blower motor.

When my BMC's failed, all I could get was defrost air, both times. Replacing the BMC's fixed the problem

==

[ranger2131]

When my BMC's failed, all I could get was defrost air, both times. Replacing the BMC's fixed the problem

==

Interesting. I guess maybe it's worth replacing the BMSC just to see?
The alternative is fastblackmerc's last post said a bad circuit board could cause air to operate only on one speed and/or to come out only certain vents. Since I have both of those problems, it's possible a bad EATC could be causing both.

But then the fan only works on high is classic BMSC symptom, and you said your BMSC also messed up which vents were operating.... so it could be causing both too.
Sounds like I'm back to square one, and replacing BMSC is cheapest route to try first if I'm going the shotgun method. Any solid way to diagnose a bad EATC board? (if not I'll probably just buy a new BMSC tomorrow to try anyway)

[GreekGod]

and you said your BMSC also messed up which vents were operating

that's not really what I said at all - Ford designed blower operation failure mode to be defrost only - it is a safety feature, especially for winter driving when it keeps the windshield clear

==

[ranger2131]

that's not really what I said at all - Ford designed blower operation failure mode to be defrost only - it is a safety feature, especially for winter driving when it keeps the windshield clear

==

Same difference. Your BSC failure trigger an emergency mode which only allowed air to come out on defrost, correct? I dont really care what the exact mode of failure is. If the system goes into emergency mode because of a bad BMSC, then the bad BMSC is indeed "causing" the air to only come out of defrost, even if indirectly.

That is a symptom I have, and a symptom that could also be attributed to o-ring failure. Since I replaced o-rings with no joy, this is a potential cause I'm willing to look at. Especially since I also have the high speed only symptom which is apparently more common to BMSC failure.

The only alternative is a bad EATC causing all of it. I hope that is not the case

[ranger2131]

I replaced the BMSC. I now have all my fan speeds back, so it was bad for sure.

Unfortunately (and predictably) the problem of blowing only out of defrost persists. Must still be a vacuum leak somewhere.

[ranger2131]

EATC self test shows 888 and all functions which I assume means no problems. So what's next to attempt to fix the air out of defrost only problem?

[ranger2131]

Did you make sure the o-rings were the proper size, installed correctly with a small amount of silicone dielectric grease, the springs were put back, the pistons are installed in the correct orientation? What is the correct orientation?

Is the red connector from the solenoid panel positioned on the system board connector the right way? What is the right way? Pics anywhere?

Do you have vacuum at the black hose at the rear of the EATC? I started engine and disconnected the vacuum lines at the white connecting harness near the firewall above the passenger footwell. Vacuum seems good from the black hose connection there... is that ok or is there more to test? :confused:

Sometimes the bad solder joints on the BCM are hard to see.

You could have a bad EATC, although it's highly unlikely there are two things wrong with it.

Figured I'd go through this again...

[fastblackmerc]

Figured I'd go through this again...

This is the way the plunger & spring are supposed to be setup
http://i167.photobucket.com/albums/u133/fastblackmerc/MM%20Mods/EATC%20Repair/Assembly.jpg (http://s167.photobucket.com/user/fastblackmerc/media/MM%20Mods/EATC%20Repair/Assembly.jpg.html)

The connector inside should be on all pins and orientated correctly. When I did mine the connector was one pin off and wasn't functioning correctly just like bad o-rings.
http://i167.photobucket.com/albums/u133/fastblackmerc/MM%20Mods/EATC%20Repair/SolenoidConnector.jpg (http://s167.photobucket.com/user/fastblackmerc/media/MM%20Mods/EATC%20Repair/SolenoidConnector.jpg.html)

[ranger2131]

Thanks for the pics! I will check again.

My plunger part is black, not silver, so that would make it easier to get one backwards. I was originally just trying to pull the tops out but the springs came with it and pulled the plungers out, which then fell to the floor on a couple of them. I honestly couldn't tell much difference in the plunger ends because they were black and it wasn't lit up like an operating room when I did it. Will have to check again later.

[ranger2131]

OK so on the plunger it looks like the narrower or lesser diameter "nipple" part goes towards the bottom and the wider "nipple" is at the top going towards the solenoid and encapsulated by the spring? Is that correct?
If so the first one I pulled was definitely oriented wrong and it was indeed much easier to see the difference (wide end vs narrow end) on the silver one in your picture vs my black ones. Your pictured plunger has contrast between the silver body and black nipple. Mine are entirely black plastic of uniform color.

I'm about to check the rest and correct if necessary. I'm hoping beyond hope that this will fix my issues :)

[ranger2131]

Hey it worked! Thanks a ton fastblackmerc!!!!

Two of the plungers were upside down. Put em back in the other way and voila- problem #2 solved. I now have air out of vents and all my fan speeds back.

The BSC was definitely more of a pain b/w the two jobs. Should I go ahead and replace the blower too? I've heard it can cause the BSC to go bad again if you don't.

Now to figure out what to do about my entire dash cluster being out :(. It went out a couple weeks ago, which is what prompted me to finally fix the a/c issues in the first place. This car is just a bundle of joy right sometimes :mad: