So about two weeks about my heater just stopped working. I turn the **** and it does nothing. Well that is not entirely true, the battery gage drops from 13V to about 9V and then blows the fuse. Can anyone help? Oh by the way it's a 82 GSL.

 

Your fan is bad? Best guess.

 

Could just be the fan case is full of debris and its stopped the motor from turning; leaves and crud can get in there over time. No such thing as 'cabin air filters' when these cars were built.

Or the fan motor could be bad as TG mentioned. Either way, first step is to pull the fan out and inspect.