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I have a 87 new yorker and the a/c works but when you give it gas from a light the a/c goes to the floor but comes back to the vents, I had this problem on older chryslers and it was a vacuum valve , but this one is digital and has only wires going to it , so does this car have a vaccum valve to control this and if it does where is it located ??
 

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Yes - it'll be somewhere in the smaller vacuum line that comes off the brake booster and goes through the firewall to the power/vacuum module for the ATC system. Don't know where exactly, but the line should be black in color.

The power/vacuum module is mounted to the front of the air box behind the glove compartment. Its job is to redirect engine vacuum to the various vacuum motors that control the blend doors.

The system has a self test you can activate by pressing bi-level, floor, and defrost at the same time until the display starts flashing.
 

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This vacuum check valve plugs into the brake booster unit and has a thin vacuum line coming off it toward the firewall. The original inadequate one is about the size of a couple of quarters stacked up. The replacement is about the size of a 35mm film canister. It just pulls out/off to replace.
 

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Original check valve should look like this, installed in the brake booster:


Upgraded check valve looks like this:
 

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If you look at the 2nd photo above, the thick vacuum line comes out of the booster to the intake manifold; the thin line comes out of the check valve at the top and goes through the firewall to the climate control selector; and the third line to the right (behind the master cylinder) goes to the cruise control servo.
 

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I do not think it's under the dash. It's been on the brake vacuum booster in every Mopar I've ever seen.

The valve might be a junkyard item, or Rockauto, or Arizona Parts (when Marty gets back from extended vacation). Auto parts stores don't have them.
 

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I only had one pre-1980s car that had vacuum climate control, and it didn't have power brakes, so I don't know how that was set up (72 Dart). The K-cars and later have the setup I described.
 

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Just found some info suggesting that the check valve is located over the airbox, behind the glove box.
 
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