Maybe the fan brushes on the blower are your problem.

A lot has been written on this site about worn brushes and a lack of heat. It only costs a couple of bucks and is an easy job, supposedly. I will be replacing them on my car sometime soon.

Search for fan brushes 123, or something like that.

Good luck

__________________
Ralph

1985 300D Turbo, CA model
248,650 miles and counting...