Cadillac: heater does not work, cadillac deville, floor vents

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The car is a 91' Cadillac Deville.
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I've changed the thermostat & check the anti-freeze, but still can't get heat. The fan runs but no heat
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MAKE-MODEL-YEAR of vehicle ?. Most likely the programmer is faulty.

Remove the glove box liner and you will see a threaded metal rod that goes from the programmer to the damper door. As you move your display panel from HEAT to A/C this rod should move back and forth. Does it.
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You did not answer my question.Yes it moves back & forth
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Is the blower motor blowing any air from any of the vents on the dash, degrost and floor vents ?. Yes


Answer
Remove the glove box liner and you will see a threaded metal rod that goes from the programmer to the damper door. Make a mark on the threaded rod where it snaps into the clip on the plastic programmer arm. Put the system on full heat and manually move this metal arm back and forth to see if you get any heat.

Put the threaded arm back in the clip where you marked it.

If you do get heat when you manually move the metal rod, Replace the programmer which is the big black box that has the plastic arm on it.

tom