1989 Volkswagen Jetta Something is wrong with the electrica

I have an 85 Jetta and had the same problem. My son bought the car 8 years ago and replaced the stock am/fm cassette with a 10 stacker CD player. He had it professionally installed. He was always having NO START problems after that and needed to charge up the battery all the time.

A couple of years later the heater core went he gave me the car.

I had problems with the battery going so low I could not start the car whenever I used the sound system. I finally had to stop using it. But, even not using it, I had to charge up my battery every couple of months. Several weeks ago, my son got a van and wanted the sound system from my Jetta, so he took it out and I have not put in anything else. I have not had any problems starting the car since then.

I think the combination of an older battery, a sound system that sucks a lot of juice, mainly local driving, and the old Jetta weak charging system all contributed to the problem. Seems you just can't "put a new patch on an old garment"

However, the fact that you blew a fuse suggests that the system has a short somewhere. Could be a wire is making contact with metal somewhere in the dash or something. If I was you, I would remove the fuse to the sound system to disengage it for a couple of weeks and see how the car starts.