93 Taurus discharges when i turn on the heater

alt died
then in 30min driving the battery dies and engine stops
the engine run off the ALT full time until the ALT dies
causing rapid battery discharge. and engine stalls.

do not replace the alternator with battery NEG lug connected of blow up ALT FUSES, never fun that.
or on newer smarter alts , it shuts down if 1 battery cell of 6 goes open or shorts, this prevents battery explosion.
so we load test the battery first. then if good the alt is bad. or we test the alt next.
this failure is super common , for 100 years.
we test the both carefully

the alt good will put 13v to 15vdc on the 2 battery lugs.
even at idle, and any dmm meter made can see that.

Have the alternator checked , not charging .

Clean battery terminals first. If still no better, get parts store to test alternator.

ran cheery, the exhaust ran red hot? LOL.
the engine runs off the alternator not the battery.
so , if the alt is bad,the battery will discharge.
the alt charge lamp glows, did it?

old post,
bad alt, or battery is no good.
try a known good battery , and make sure the
voltage across the battery is 13.3v to 15vdc running.
if not the ALT System is bad, notice I said system.

btw , replaced means nothing to me.
new , used, rebuilt, recycled, , what?

What is the idle speed? Are you sure the belt is routed correctly?

You mean with the engine running? If the engine is running, the heater fan should be getting power from the alternator, not the battery. Does your battery light go off after engine is running? Or does the voltage gauge show normal charging when running?
If you can start the truck, have your charging system checked out. If it won't start now, have the battery charged up and try again. Then have the charging system checked. If it is good, your heater fan may have a short and drawing too much current, But a heater fan will run the battery down pretty quick, if the engine is not running.

I need more info for your problem. Never should an alternator charge over 13.8 and they will charge less depending on demand. As long as the battery voltage is above 11.5 volts the car is probably within min operating specifications.

you have to remove the dash. i suggest you go to an auto parts store and buy an after market tech manual. by the way everything under that smooth dash is sharp and give yourself a good weekend to complete. GOOD LUCK.

what i think is you problem is the device attached the one door latch and need to be replaced for a new one,you can get them from the dealership and the are not expensive,this device is the one turn your lights on(interior) when you open de doors

that sounds about right . the voltmeter just tells you how many volts the battery is holding,if you turn your lights on high beam turn your wipers on and your heater all at the same time,as soon as the current being used is greater than the alternator can charge , you will see the needle on the voltmeter drop back that is normal and logical. if you are running spotlights etc you may need a higher wattage alternator a lot of vehicles come out with 55watt alts.and the owners change the alts. to 100 watt alts... NOW as long as yours is not dropping below 12volts it is not draining your battery so there will be no ill effects it just means the alternator is working close to its capacity-------------------- there you go ,I would not be worrying too much unless it flatens your battery Idony think you need worry "youdoit"