heater causing to much battery draw?

[cmyc5575]

As some of you guys know I had an issue with my lights dimming and causing me to have to replace my alternator over the weekend bc of the thought of the battery getting drained! But it did it again on my way home last night with the heater on all the lights started to dim, I turned off the heater and and the lights brightened up and turn signals started working just fine like nothing happened. Any comments or advice is much appreciated. Thanks guys!