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Thread: EATC and BCM are fine yet air only blows out vents

  1. #1

    EATC and BCM are fine yet air only blows out vents

    I've read all the threads related to both EATC and BCM. I have a 05 Sport and an 03 MM.

    The 05 sport is having the issues. I swapped out the EATC and problem on Sport persists.

    I can hear the blend door moving when moving from floor to vents to defrost. AC works, Max AC works as it should, getting hot air when set to appropriate temps, airflow control is as it should be in each location. EATC diagnostics comes back clean. But the air flow when set to floor or defrost is coming out the vents. I am getting a mix of floor and vent on heat. and a mix of defrost and vent when on defrost. something isn't fully sealing when the blend door moves or something along those lines.

    Can someone help me narrow this further? Thanks!

  2. #2
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    Quote Originally Posted by DeadVic View Post
    I've read all the threads related to both EATC and BCM. I have a 05 Sport and an 03 MM.

    The 05 sport is having the issues. I swapped out the EATC and problem on Sport persists.

    I can hear the blend door moving when moving from floor to vents to defrost. AC works, Max AC works as it should, getting hot air when set to appropriate temps, airflow control is as it should be in each location. EATC diagnostics comes back clean. But the air flow when set to floor or defrost is coming out the vents. I am getting a mix of floor and vent on heat. and a mix of defrost and vent when on defrost. something isn't fully sealing when the blend door moves or something along those lines.

    Can someone help me narrow this further? Thanks!
    You said you read all the posts, did you replace the o-rings?

    Have you checked for any loose hoses or vacuum leaks?
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  3. #3
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    Sounds like the EATC is controlling vents like it should but the air temperature isn't being controlled properly. Maybe the blend door actuator.
    Thanks to Darrin @ BC Automotive:
    $1800 and it was worse than when he started!

    Brian (FordNut) FPG # 1458 of 7838
    03 MM 300A (Lotsa mods, 130k mi) was 303rwhp/318rwtq N/A
    then 476/410 D1SC ProCharged on stock block
    then 660/555 D1SC PC on 5.3 wet sleeved Teksid alum big bore stroker
    then 365/369 N/A on 5.3 wet sleeved Teksid alum big bore stroker
    Now 751/617 3.4L Whipple on 5.3 Boss5.0 iron big bore stroker

    03 MM 300B Silver (Mostly stock, originally wife's car, 370k mi) FPG # 7053 of 7838 or 49 of 417 SB
    03 MM 300B Silver, Stock, wife's next one, 136k mi FPG # 7134 of 7838 or 89 of 417 SB
    04 MM Silver, Stock, on standby 85k mi, FPG # 1212 of 3214 or 432 of 997 SB
    01 F150 longbed
    01 F150 shortbed
    00 F150 4x4 stepside
    01 F150 4x4 7700
    68 Stang FB (70 351C 4V, 4 wheel discs, project car)

    Mods listed here (some items not current): FordNut's Mods

  4. #4
    Yes, I did change the o rings first. it didn't work. so I then swapped a known working EATC (out of my MM) into the Sport. Sport continues to have same issue with working EATC.

    I have not tested for other vacuum leaks

  5. #5
    Join Date
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    I guess other vacuum leaks are a possibility, check out on the firewall where the vacuum manifold connects to the intake manifold. I got kind of confused by this:

    "airflow control is as it should be in each location..... But the air flow when set to floor or defrost is coming out the vents."
    Thanks to Darrin @ BC Automotive:
    $1800 and it was worse than when he started!

    Brian (FordNut) FPG # 1458 of 7838
    03 MM 300A (Lotsa mods, 130k mi) was 303rwhp/318rwtq N/A
    then 476/410 D1SC ProCharged on stock block
    then 660/555 D1SC PC on 5.3 wet sleeved Teksid alum big bore stroker
    then 365/369 N/A on 5.3 wet sleeved Teksid alum big bore stroker
    Now 751/617 3.4L Whipple on 5.3 Boss5.0 iron big bore stroker

    03 MM 300B Silver (Mostly stock, originally wife's car, 370k mi) FPG # 7053 of 7838 or 49 of 417 SB
    03 MM 300B Silver, Stock, wife's next one, 136k mi FPG # 7134 of 7838 or 89 of 417 SB
    04 MM Silver, Stock, on standby 85k mi, FPG # 1212 of 3214 or 432 of 997 SB
    01 F150 longbed
    01 F150 shortbed
    00 F150 4x4 stepside
    01 F150 4x4 7700
    68 Stang FB (70 351C 4V, 4 wheel discs, project car)

    Mods listed here (some items not current): FordNut's Mods

  6. #6
    Sorry about the confusion. I should have said "AirTEMP control is as it should be in each location. The air flow when set to floor or defrost is coming out the vents".

    I retraced my steps, lubed the orings a bit (did them dry last time) and no change.

    I run the car, run the HVAC, shut the car off and then I can hear a hissing air "leak" under the hood. coming from the area around the intake. Is this normal upon shutting the car off? I don't think it is but am unsure.

    Thanks for your help. I appreciate it.

  7. #7
    Join Date
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    Location
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    I'll take a stab at it...

    The square plastic black box on top of the driver's wheelwell is the vacuum reservoir. If you're hearing hissing from that area, check to be sure it isn't damaged or the hose is cracked. There's also a check valve in the line coming from the intake manifold, but I'm not sure where that's located.

    If your temperature can be regulated properly, but the direction of the air is wrong, the the blend door is fine; it's the "floor/defrost" door and/or the "panel" door vacuum motors and circuits you should be looking at. Those are labelled as vacuum circuits 2, 3, and 4 from the EATC.
    Last edited by RF Overlord; 12-12-2010 at 11:58 AM.
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