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Green96
09-07-2013, 05:02 PM
I just replaced the o-rings in dad's EATC. It was going crazy sending AC to the defrost ports. After the fix everything appeared OK, but I think he still has an issue.

With normal AC on, nothing happens when I select Max AC. No blower speed increase, no blend door change that I can detect.

With the HVAC off, the blower speed increases over normal speed when Max AC is selected and slows back down when I switch to normal AC.

Is this simply a BCM problem? He has a replacement BCM in hand, but has been waiting for his to fail before going to the hassle of installing it.

Where is the recirculation bland door? I would like to watch it while I go from one AC mode to the other.

Any other thoughts? This is on a 2004 GM by the way. Thanks

MyBlackBeasts
09-07-2013, 06:33 PM
I just replaced the o-rings in dad's EATC. It was going crazy sending AC to the defrost ports. After the fix everything appeared OK, but I think he still has an issue.

With normal AC on, nothing happens when I select Max AC. No blower speed increase, no blend door change that I can detect.

With the HVAC off, the blower speed increases over normal speed when Max AC is selected and slows back down when I switch to normal AC.

Is this simply a BCM problem? He has a replacement BCM in hand, but has been waiting for his to fail before going to the hassle of installing it.

Where is the recirculation bland door? I would like to watch it while I go from one AC mode to the other.

Any other thoughts? This is on a 2004 GM by the way. Thanks

The only difference between Max a/c & regular is when set to Max the door for fresh outside air is closed and the cabin air is recirculated thru the evaporater. Max is used to bring the cabin temp down quickly like when car has been parked in the sun for a while. When temp is reduced you are supposed to swith back to normal a/c so you bring in fresh air and don't deplete the oxygen level in the cabin.

Green96
09-07-2013, 06:39 PM
The only difference between Max a/c & regular is when set to Max the door for fresh outside air is closed and the cabin air is recirculated thru the evaporater. Max is used to bring the cabin temp down quickly like when car has been parked in the sun for a while. When temp is reduced you are supposed to swith back to normal a/c so you bring in fresh air and don't deplete the oxygen level in the cabin.

On my mm the blower speeds up when I select Max. It is either internally turning up the blower, or there is less load on the blower when it is in recirc mode allowing it to go faster.

MyBlackBeasts
09-07-2013, 06:43 PM
On my mm the blower speeds up when I select Max. It is either internally turning up the blower, or there is less load on the blower when it is in recirc mode allowing it to go faster.

Yes, it engages high speed.

Hi speed is hi, no difference from high BM speed with normal a/c on high.

It sounds higher because of the change to recirc air but that is just an "audio illusion".

stangracr
09-08-2013, 07:40 PM
If you end up needing a control head I have one that is maybe a year old. Bought new from Ford. $200.00




ed

tbone
09-09-2013, 06:45 PM
My guess is that the EATC is bad. I had to replace mine. The circuit board fried.

clintons4
09-13-2013, 07:10 PM
Mine seems to do the same thing. Its either that or its that damn hot in Houston that the A/C has a hard time keeping up. I don't have anything (another MM) to compare it to. :confused: Pisses me off because my Silverado gets cold enough to hang meat in it.

Green96
09-13-2013, 08:09 PM
I spent a little more time with it last weekend. The recirc door is not moving. It could be the door/door actuator itself, but my money is on the solenoid in the EATC. I bet I did not get that one quite right when I did the repair. I am going to try again soon. I should be able to figure out which one goes to the recirc door.

MyBlackBeasts
09-13-2013, 09:05 PM
I spent a little more time with it last weekend. The recirc door is not moving. It could be the door/door actuator itself, but my money is on the solenoid in the EATC. I bet I did not get that one quite right when I did the repair. I am going to try again soon. I should be able to figure out which one goes to the recirc door.

That sounds very plausible & would be the 1st thing I'd look at.

Good luck! :D