Replace the thermostat to get more heat. As far as it only coming from the defroster, check for vacuum leaks under the dash. The air flow is controled by vent doors in the HVAC system. If they don't have enough vacuum, it usually will default to the defroster.
As far s the rear defroster, I believe you hear the relay clicking. Locate where the noise is coming from and replace the realy.
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Monday, March 22nd, 2021 AT 12:56 PM