HVAC air only comes out of the defroster

[Black Machine]

I have a 03 Merc Marauder. Over the winter I noticed that if I had the heat on in my car coming through the dash vents that under acceleration the air would stop coming the vents and come out of the defroster. This issue has gotten progressively worse to the point that now the A/C is only coming out through the defroster and floor. Is this a malfunction blend door motor?:confused:

[Logizyme]

I'm also getting the same issue. I suspect it may be the fault of the ETAC O-rings that are always talked about, but I've never familiarized myself with the issue.

[Bluerauder]

I have a 03 Merc Marauder. Over the winter I noticed that if I had the heat on in my car coming through the dash vents that under acceleration the air would stop coming the vents and come out of the defroster. This issue has gotten progressively worse to the point that now the A/C is only coming out through the defroster and floor. Is this a malfunction blend door motor?:confused:

This is a classic indication of the EATC O-Ring problem. I had the same symptoms under acceleration. 03mmmonroe replaced my O-Rings at MV9 in Hershey, PA. Was back to operating properly after the fix. Took only 20 minutes in the hotel parking lot .... but Russ has lots of experience replacing the O-Rings. That was in October 2011 and I haven't had a problem since then.

[fastblackmerc]

I have a 03 Merc Marauder. Over the winter I noticed that if I had the heat on in my car coming through the dash vents that under acceleration the air would stop coming the vents and come out of the defroster. This issue has gotten progressively worse to the point that now the A/C is only coming out through the defroster and floor. Is this a malfunction blend door motor?:confused:


I'm also getting the same issue. I suspect it may be the fault of the ETAC O-rings that are always talked about, but I've never familiarized myself with the issue.

Your EATC(s) need to be repaired.

I can repair it and upgrade the button and fan lights to LEDs.

PM me.

[RF Overlord]

Is this a malfunction blend door motor?This bears repeating:

The ONLY function of the blend door is to regulate the amount of heat or cold. It has NOTHING to do with which vents the air comes out of.

[justbob]

What oil is recommended for the blend door? 4w10 or 3w55? So confused. [emoji20]





















Had to. [emoji13]


Builder Of Badassery

[fastblackmerc]

This bears repeating:

The ONLY function of the blend door is to regulate the amount of heat or cold. It has NOTHING to do with which vents the air comes out of.

The blend door regulates the air temperature as called for by the EATC. If you only getting hot or cold air the blend door actuator needs to be replaced.

The EATC controls the fan speed, temperature, and where the air comes out... floor, vents, defrost or a combination of them. If the air comes out the defrost ONLY, your EATC needs to be repaired

If the fan doesn't work or doesn't change speed as required you probably need the BCM.

[Marauderman]

The blend door regulates the air temperature as called for by the EATC. If you only getting hot or cold air the blend door actuator needs to be replaced.

The EATC controls the fan speed, temperature, and where the air comes out... floor, vents, defrost or a combination of them. If the air comes out the defrost ONLY, your EATC needs to be repaired

If the fan doesn't work or doesn't change speed as required you probably need the BCM.

I will drive 3 hrs for him to fix anything and drive back 3 hrs. ( and done it several times btw) so I know it is fixed right--todays situations with this car requires it....know this man well....carry on Bro.............

[Logizyme]

Mine is actually mostly just blowing on the floor.