why is the floor heat not working

Asked by Jan 05, 2013 at 10:37 AM about the 2006 Mercury Grand Marquis LS Premium

Question type: Maintenance & Repair

The air conditioner works since have $500.00 put into it last summer. But now that winter is here, the floor does not have any heat, the dashboard blows out hot air, but none on the floor, it feels like the AC is on.

2 Answers

90,065

There are doors in the heater box that direct the air. Those doors are moved by vacuum motors. The vacuum comes from the engine through a hose. Check your hoses for leaks because your doors are not moving.

1 out of 1 people think this is helpful.
345

Had similar problem w/ '01 Gr. Marq. Probably need to replace vacuum motor (<$20) under dash as I did - fairly easy repair. Vacuum motor is double-acting, meaning separate hoses are feeding vacuum to two different diaphragms on each side of the motor. My motor was working on one side (like yours) so I was getting heat out of dash but not on floor. Thought vacuum motor must be ok if it was moving air door at all but after some research found out that air door was only moving one direction. You can usually hear some type of "whistling" or "hissing" noise when activating controls to move air to floor b/c it's likely the diaphragm has a hole in it (if that's your problem). You may have to remove plastic shrouds under dash before you can hear the noise.

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