Repeated FSU failures 08 328I convertible

I am experiencing repeated FSU failures in my 08 328I convertible. I am going on my 5th replacement. The replacements work well for a short time then quit. Heater fan will not turn on at all. The FSU shows burn marks at the spade terminals. Could it be the quality of aftermarket replacement parts? It could be. Is there a difference in the units that BMW dealerships sell? These units do run up in temperature being resistor units, maybe insulation quality is not up to par. However I have a dealership vs internet replacement both with the same problem (burn marks at the spade terminals). What gives? Anyone have a photo of the wiring harness attachments to the FSU so I can make sure there are no factory wiring screwups. Factories make wiring errors all the time. Are resistor units polarity sensitive? If the red and brown wires were inadvertently reversed for example?

What is an "FSU?"

I think Jimbo Fisher is the source of such failures.

Typically when I have seen this failure it is ALWAYS the fan pulling way more amps and the fuse will not always fail to protect it.
I would also use a good dab of dielectric grease to improve the connection because DC arcing isn't normal at all. I would imagine replacing the fan is a PITA as is the case in all 3 series BMWs.
Multiple FSU failures points right to the fan...

Originally Posted by fun2drive

Typically when I have seen this failure it is ALWAYS the fan pulling way more amps and the fuse will not always fail to protect it.
I would also use a good dab of dielectric grease to improve the connection because DC arcing isn't normal at all. I would imagine replacing the fan is a PITA as is the case in all 3 series BMWs.
Multiple FSU failures points right to the fan...

+1

I bet if you drove around long enough with the fan on the max setting it will blow the fuse.