What makes your lights go dim while driving when the heater and radio is on or off

tell all that works and does not work not just the bad
electric and fuses run off huge power buss.
even 10 things off 1 fuse
so telling it all makes the job 10x more easy see?
dim head lamps high and low beams?
horn dead.
but does car start run and drive,???

is key dead? engine dead. , heater blower dead
radio dead. ???????? key starter motor sounds strong and fast cranking the engine to start it?

no car told to the blind, Wiz of OZ can't see outside the curtains
make, model , year.
fuse are first
does car drive ok day time,
radio play
heater/AC blower blow ok.
head lamps dead.?
PARK LAMPS DEAD ALL SIDES OF CAR FRONT/REAR./LEFT /RIGHT

MAKE, MODEL, YEAR, PLEASE!
WE HAVE NO #@$!@$! CLUE IF YOU DON'T GIVE US ENOUGH INFORMATION TO START FROM!!!

I have no idea why the heater would turn off.
The radio lights are supposed to dim when the headlights are turned on, so try to follow the circuit that tells the radio the headlights are on.

You have a bad ground. Most are behind the side kick panels.

sounds silly but did you try using the dimmer switch, either the light or on the dash usually on the left. litlle wheel that dims the dash and radio lights.

first thing to check would be your ground wire,then check to make sure your battery terminals are not corroded, if after all that have them check your alternator

Your alternator may be going bad. Once the car is running, your battery has done its job and the alternator takes over. The alternator is responsible for firing the plugs, running your lights, your radio, your heater/AC, and anything else electrical, as well as keeping your battery charged. If the alternator is on its way out (or even has a less than good ground), you may experience some lights dimming, or even choppy radio signal. If the alternator is already gone, and your car is running off of the battery full time, you will also get the dimming you describe, and sooner or later the car will not even start. Take your car to an auto parts store (Advance, or Auto Zone, etc) and ask them to test your alternator. This is a free service.

what happens when you turn the knob to brite/dim the dash lights?

Sounds like a dead short. Disconnect the power to the radio and try the rear defog. Then to determine if it is the radio or the hater, disconnect the heater and put power to the radio. Another simple test is to, at night have the head lights on, turn the radio on see how much the lights dim. Then with the radio off, turn the rear defog on. Then try both. IF either one makes the head lights dim and not recover after a minute or so that devise is the shorted component. Check grounds on the radio and the heater.

i have replaced my dimmer roller switch to solve my problem with the dash bord light flickering and dimming by them selfs .. that or just flip (smack) the roller switch for temp inprovement untill you decide to install a new dimming switch..?