BMW Repair: 1989 bmw 525i heater control question, coolant leak, bmw 525i

Question
hello John, My E34 is in very good condition compare to the years of the car is very well kept from the date of production until now. I usually keep this car Stored during the months of winter here in Canada, and get it on the road on April. But before I stored the car in the garage I spotted a coolant leak but it did not bother me then but know that the summer is close i want to have the car ready for summer. I wanted to ask you about this coolant leak but after many reading and learning from mechanics I have come to a exact location of the Leak. The leak was coming from under the car exactly above the Transmission there are two opening holes on both sides of the frame and those opening are from the HEATER CORE which they are used as a A/C drains but I was getting coolant from the drain in the left. Since I am about to replace the Heater Core my-self I am considering some hints you can give me during my removal of the Heater Core something to be aware off. Since I am replacing the Heater Core I have had this problem with the Heater Knobs(Heater Control Unit) When I have the car out in the cold when i go and start the car most of the time I don't get any sign of blower turned on my vents, even if the temp knob is on the 4th speed so no Hot or Cold air. I have been told to check a resistor because of the car age it could be shorting(no good contact) and need to be soldered. Please can you help me with the location of this sensor since I am working in the heating unit.

Looking forward to your Answer

I Really Appreciate your help  

Answer
Heater core replacements are big jobs, but nothing tricky.  Take LOTS of pictures as you go, and keep screws, fasteners, etc. with the parts they came from.  I did a '95 740 a few months ago.

Your fan sounds like a bad resistor (not sensor). Not sure where it's mounted on an e34.  www.roadfly.com can help.

Replace the other items that make sense as you come across them.  Good luck!