Thinking BCM, but want to make sure

[SC Cheesehead]

Was heading home from church this morning and noticed the blower fan was going wide open. Auto temp control was set at 70*, outside air temp was around 50*, but the car was fairly warn inside due to solar heating through the glass.

Tried changing temp settings and fan speed (both via steering wheel and dashboard board) but no response from the changes. Fan speed stayed at high at all auto temp settings, same for ranging the speed controls.

Air temp is cool, but not real cold. Can get the air flow to change from the dash panels to defrost, but not will not shut off.

Checked through EATC and BCM threads, symptoms seem to relate to issues with both. Not adverse to fixing both EATC and BCM if I have to, but would rather attack primary problem first; any thoughts on the best way to proceed?

[MrBluGruv]

I'd try to run the diagnostic from the control unit first, it's been known to at least temporarily cure some wild issues with the A/C system.

I can't recall it off the top of my head though. :(

[tbone]

Try tapping on the bcm.

[fastblackmerc]

I'd try to run the diagnostic from the control unit first, it's been known to at least temporarily cure some wild issues with the A/C system.

I can't recall it off the top of my head though. :(


Try tapping on the bcm.

What they said^^^^^^^^^^^^^^^

Let me know if you still can't get it to work.

[SC Cheesehead]

Hey guys, thanks for the suggesstions, will do.

[Mr. Man]

Probably God's way of punishing you for going to the Church of Dunkin' Donut's

[SC Cheesehead]

Tried tapping on the BCM, no luck.

Blend door's working okay, as air flow will alternate between defroster, dash, and floor vents depending upon settings selected.

Fan won't change from high, even when I push the "off" button (air sure howls, though!)

Gonna go with a replacement on the BCM.

Jim, you want me to send you the old unit for a core?

[fastblackmerc]

Tried tapping on the BCM, no luck.

Blend door's working okay, as air flow will alternate between defroster, dash, and floor vents depending upon settings selected.

Fan won't change from high, even when I push the "off" button (air sure howls, though!)

Gonna go with a replacement on the BCM.

Jim, you want me to send you the old unit for a core?

Sure, send it.

The blend door "blends" the hot & cold air to get the temp you set in the EATC.

If the air changes between the floor, dash and defroster vents then the solenoids in the EATC are working correctly.

[SC Cheesehead]

Sure, send it.

The blend door "blends" the hot & cold air to get the temp you set in the EATC.

If the air changes between the floor, dash and defroster vents then the solenoids in the EATC are working correctly.

Cabin heated up okay this morning, so the EATC appears to be functioning, but no response to changing either the temp or fan settings; fan continues to run on high. I'll let you know status after I get the BCM replaced.

[Blackened300a]

Cabin heated up okay this morning, so the EATC appears to be functioning, but no response to changing either the temp or fan settings; fan continues to run on high. I'll let you know status after I get the BCM replaced.

Good luck, its not fun reaching behind there to replace it.

[SC Cheesehead]

Good luck, its not fun reaching behind there to replace it.

Tell me about it; especially with a big ol' M112 sitting in the way... :(

[SC Cheesehead]

Update.

Not the BCM :shake:

EATC pulled and enroute to fastblackmerc for him to do his magic...:D

[jstevens]

Wow, so the EATC can make the ran run on high. One more thing to keep an eye out for.

[MinnesotaMuscle]

Huh! I have this same problem and was going to blindly pick up a new BCM, but I replaced it once last summer. This is interesting to know as I have been meaning to fix my EATC defrost only issue. I wonder if I should attack the EATC before dropping money on another BCM. Let us know what Jim finds...

Jim - what else can you do with the EATC besides the 0-ring fix??? As I'm sure the o-rings wont cause the fan to stick on high...

[fastblackmerc]

Huh! I have this same problem and was going to blindly pick up a new BCM, but I replaced it once last summer. This is interesting to know as I have been meaning to fix my EATC defrost only issue. I wonder if I should attack the EATC before dropping money on another BCM. Let us know what Jim finds...

Jim - what else can you do with the EATC besides the 0-ring fix??? As I'm sure the o-rings wont cause the fan to stick on high...

The failure of the o-rings might cause the fan to stay on high if there is enough of a vacuum leak.

Enough of a vacuum leak = defrost only, heat only & fan on high.

[CBT]

Good luck, its not fun reaching behind there to replace it.
That's wh....eh, nevermind :D

[SC Cheesehead]

The failure of the o-rings might cause the fan to stay on high if there is enough of a vacuum leak.

Enough of a vacuum leak = defrost only, heat only & fan on high.

RF Overlord, one of our resident electronics wizards (not to mention an all around swell guy) provided me with the following troubleshooting info on the "high fan" issue that has hit several of us.


"Does the fan keep running even when the EATC is turned off or does it turn off with the EATC, but runs only on high when the EATC is on?

If the fan still runs even when the EATC is turned off, then try this: the three control wires from the EATC to the BCM are on C228b, which is the connector closest to the driver's side on the back of the EATC. Try unplugging that...if the fan still runs, it's either the BCM or the wiring from the EATC to the BCM. If it stops, then it's the EATC.

If the fan doesn't stop when you disconnect C228b, then there might also be a short to ground on the wire coming from the BCM to the blower motor itself...that would allow the fan to run at max speed all the time. If you can disconnect the BCM and the fan still runs, then it's the wire from the BCM to the blower that's shorted to ground. Connector C1227 is the plug on the blower motor and Pin 2 is the wire from the BCM. It's a 10AWG OG/RD wire. Unplug it from the blower motor and see if you have very low resistance between that pin and ground. With the BCM connected, that pin should not read completely open as there is a voltage divider resistor internal to the BCM on that wire, but it should not read very low resistance, either. With the BCM unplugged, then that pin 2 on C1227 should read open."

The fan went off when I unplugged C228b, so based on Bob's info, I'm going to replace the EATC with a used unit to see if that resolves the issue. If it does, then I'll have new o-rings installed in the replacement EATC before I button everything back up.

[fastblackmerc]

RF Overlord, one of our resident electronics wizards (not to mention an all around swell guy) provided me with the following troubleshooting info on the "high fan" issue that has hit several of us.


"Does the fan keep running even when the EATC is turned off or does it turn off with the EATC, but runs only on high when the EATC is on?

If the fan still runs even when the EATC is turned off, then try this: the three control wires from the EATC to the BCM are on C228b, which is the connector closest to the driver's side on the back of the EATC. Try unplugging that...if the fan still runs, it's either the BCM or the wiring from the EATC to the BCM. If it stops, then it's the EATC.

If the fan doesn't stop when you disconnect C228b, then there might also be a short to ground on the wire coming from the BCM to the blower motor itself...that would allow the fan to run at max speed all the time. If you can disconnect the BCM and the fan still runs, then it's the wire from the BCM to the blower that's shorted to ground. Connector C1227 is the plug on the blower motor and Pin 2 is the wire from the BCM. It's a 10AWG OG/RD wire. Unplug it from the blower motor and see if you have very low resistance between that pin and ground. With the BCM connected, that pin should not read completely open as there is a voltage divider resistor internal to the BCM on that wire, but it should not read very low resistance, either. With the BCM unplugged, then that pin 2 on C1227 should read open."

The fan went off when I unplugged C228b, so based on Bob's info, I'm going to replace the EATC with a used unit to see if that resolves the issue. If it does, then I'll have new o-rings installed in the replacement EATC before I button everything back up.

Rex, you can just swap out the solenoids from yours to the used unit.

BTW... RoyLPita has one for sale I think.

[SC Cheesehead]

Rex, you can just swap out the solenoids from yours to the used unit.

BTW... RoyLPita has one for sale I think.

Good point... :o -----> ;)

I've got a line on one from another member, but will PM RLP as well, want to get this resolved before KY.

[SC Cheesehead]

Good point... :o -----> ;)

I've got a line on one from another member, but will PM RLP as well, want to get this resolved before KY.

A quick update on my EATC issues. After much wailing and gnashing of teeth, I'm back in business.

A huge THANK YOU to RoyLPita, fastblackmerc, and RF Overlord for their help and support. A couple things to pass along:

1. If you only get air through the defrost vents, problem is the O-rings.

2. If you get air through all the vents, but it's either all hot, or all cold, you're prolly looking at a circuit board issue in the EATC.

3. If you have a fan issue with the fan running at high speed, and not lowering via either the dash or steering wheel switch, or not shutting off when you attempt to power down the EATC, you could have a problem with the BCM, or possibly with the EATC. Before jumping right into replacement of the BCM, pull your EATC out of the dash, with the unit pwered up, remove the male plug closest to you (the black one). If the unit goes off, you have an EATC circuit board issue. If it stays on, you either have a BCM issue or a ground problem. Per RF:

"...[I]f the fan still runs, it's either the BCM or the wiring from the EATC to the BCM.

If the fan doesn't stop when you disconnect C228b, then there might also be a short to ground on the wire coming from the BCM to the blower motor itself...that would allow the fan to run at max speed all the time. If you can disconnect the BCM and the fan still runs, then it's the wire from the BCM to the blower that's shorted to ground. Connector C1227 is the plug on the blower motor and Pin 2 is the wire from the BCM. It's a 10AWG OG/RD wire. Unplug it from the blower motor and see if you have very low resistance between that pin and ground. With the BCM connected, that pin should not read completely open as there is a voltage divider resistor internal to the BCM on that wire, but it should not read very low resistance, either. With the BCM unplugged, then that pin 2 on C1227 should read open."

Thanks alot guys!

http://www.biggestloserresort.com/uploads/images/logo-life-is-good.gif

[Lou]

I have a problem where the fan does not turn on no matter what setting I put it in. I did the EATC tix last year so I know my o-rings are still good.

Where is the BCM located?

[RF Overlord]

It's on the firewall behind the passenger-side head. It's a PITA to access, but it can be done.

[fastblackmerc]

It's on the firewall behind the passenger-side head. It's a PITA to access, but it can be done.

It close to where the heater hoses go into the heater core.

[GreekGod]

...1. If you only get air through the defrost vents, problem is the O-rings"...

I believe the default for BCM failure is defrost on, at high speed only (direct to ground). That's what happened to mine, and the OEM o-rings were fine. As I understand it, the lower speeds are controlled by the BCM pulsing the voltage to the motor.

[SC Cheesehead]

I believe the default for BCM failure is defrost on, at high speed only (direct to ground). That's what happened to mine, and the OEM o-rings were fine. As I understand it, the lower speeds are controlled by the BCM pulsing the voltage to the motor.


Agreed with BCM speed control in general, but there is circuitry within the EATC that will impact speed as well. I had an issue with mine after replacing the o-rings, still ran high fan only, even after switching out the BCM. Switched to a different EATC and fan speed control returned.

[GreekGod]

Agreed with BCM speed control in general, but there is circuitry within the EATC that will impact speed as well. I had an issue with mine after replacing the o-rings, still ran high fan only, even after switching out the BCM. Switched to a different EATC and fan speed control returned.
Someone did a very poor job engineering the whole system, and further proof is that they haven't come up with a fix (other than replacing with replacement modules that are still defective in design & engineering). It would be nice if a smart attorney would come up with a class action lawsuit.

[Lou]

It's on the firewall behind the passenger-side head. It's a PITA to access, but it can be done.


It sure is a PITA to get to. It took me at least 2 hours not counting the trip to the dealer for the new BCM.

Anyway, it works now.

[GreekGod]

It sure is a PITA to get to. It took me at least 2 hours not counting the trip to the dealer for the new BCM.

Anyway, it works now.

Just think, next time you will be able to do it in only one hour!