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Old 08-24-2015, 11:55 AM   #1
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Car ventilation system

I have a 2008 Mercury Grand Marquis. Does anyone have a diagram of how the venting works? Here is my problem.
First of all, the blend door actuator failed about 2 years ago in full heat mode. It moves back and forth between heating and air conditioning. I took it to a dealer and they told me the actuator is located on top of the vent chamber under the dashboard and hence, since they have to completely dismantle the dashboard to get to it, it would cost $700 to $1000 to fix it.
Since I live in Michigan and need the heater about 9 months of the year and the A/C about 2, I said screw it and lived without the A/C.
So just recently, Iíve noticed that hot/warm air is coming out of the floor vent (and occasionally the defrost vent too). The faster I drive, the more air comes out. This is with the climate system off, so there is no fan running. Apparently there is a damper the moves back and forth between recirc air and outdoor air. I think this damper has failed, or at least is only OCCASIONALLY moving. I had noticed for a few months that whenever I shut the engine off, there was a creaking sound coming from the glove box. I assumed this was the outdoor air damper opening and it would close when the car started back up. It has since stopped, or occasionally I hear the creak, like it is struggling to move.
Is that correct? Does the outdoor air damper automatically open when the car is parked?
And is the outdoor air damper separate from the damper that controls which vent the air comes out of? If I press the defrost/vent/floor buttons the air still moves back and forth and comes out the correct opening, but I can still feel warm air coming out the floor opening regardless of which opening the fan is blowing air out of.
So Iím trying to figure out exactly how many dampers there are, and if the outdoor damper has its own actuator, is it possible to reach it? I canít reach the blend door, but wondering if the outdoor damper is in a different place and is accessible through the glove box? Is it possible to just crank it closed? Is there any reason I need it to be open? When Iím running my heater Iíd rather just recirc the air in the car.
What if I block the air intake vents at the bottom of the windshield? Can that hurt anything?
I miss the old days when we had a lever we could move back and forth on the dash!
Iíd like to get it fixed but if this is a dash tear down like the blend door, itís going to cost a lot!
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Old 08-28-2015, 07:03 AM   #2
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Re: Car ventilation system

Automotive A/C Engineer with:
'99 IH 4700 Toy Hauler
(2) '95 GEO Prizms both maroon
'99 GMC Yukon
'95 Chev 3500, 454 Dually Crew Cab- 145k miles-
Wife's Camel trailer puller.
'94 Astro- 370k miles
'94 Firebird Formula- 5.7L 180k miles- gone-
'92 Chevy Lumina Van 3.8L 264k
'86 GMC S-15 - 2.8L 154k
'87 Buick Park Ave . 187k
'86 Buick Park Ave 3.8L 199k miles- gone
'77 Chevy Vega- 2.5L 175k miles gone but not forgotten
'68 Camaro 396 4 spd RS/SS -72k miles-
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