E36 series: Heater Control Unit

I first enquired about this last November, and had helpful responses explaining that there were two major causes of problems with the heater control unit:
#1 A capacitor in the unit itself #2 A 'final stage resistor'.
I'm embarrassed to say that I've only now got my act together on this. Back in winter I did remove the unit and obtained a replacement capacitor with the intention of fixing it myself - but chickened out, nervous not about the dismantling and re-assembly!
I've been living with it ever since. Up until a few weeks ago it was bearable, but it got so bad recently that yesterday I sent it away for repair of fault #1 (45). Now await its return.
But it seems I *also* have fault #2. The fan is erratic, and has been so for some time. For instance, directly after the unit was removed, on switching on the ignition the fan was blowing (quite strongly), which is the correct default. This morning, nothing. (That squares with what I was getting in recent weeks, except of course that in that case the scenario was complicated by the erratic behavior of the heater control unit too.)
Last time, Jeremy said: "On the E39 similar symptoms may be experienced if the "final stage resistor" (aka hedgehog) fails - part for the E39 is circa 50 IIRC and quite DIY-able (although fiddly)."
And JB said: "I've come across this same problem [#1] and also one with the sensing thermistor several times."
Are these two, "final stage resistor" and "thermistor" one and the same thing? I suspect so, as a thermistor is essentially a resistor which changes its resistance with temperature. Or is it in fact a *diode*, which I've also seen mentioned? (The voltage drop across a varies with temperature, and is often therefore used as a temperature sensor.)
In either case, can anyone give me full details please? In particular, is the component accessible? And can I get a suitable thermistor (or diode) myself, rather than pay no doubt exorbitant BMW prices?
Any practical help would be appreciated please.
--
Terry, West Sussex, UK

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http://forums.bimmerforums.com/forum/showthread.php?p349096
or Google "bmw final stage resistor" and and go to the first one. It goes to the link above.
Bill in Omaha '86 535i
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Thanks Bill. Looks hard work!
--
Terry, West Sussex, UK


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About 30 minutes. The hard part is twisting in the small space. I did the wife's '98 528i and it's on the right side (U.S. passenger). It was truly WAY up in there. It did come out easy, though.
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