Hiya, Recently the heater stopped working on my '80 300SD

The blower comes on, but just blows cold air.
there is sufficient coolant in the tank, the car warms up fine to 80C.
but no heat inside whatsoever.

Any suggestions on things to check?


Also:
The car seems to have a small lack of power, especially at low speeds, accelerating away from a stoplight is a bit slow.

There is absolutely no smoke visible in the mirror until around 3500rpm (I don't rev her that high often), at which point it creates black fog like mad.

I've heard it said that you should see some smoke if you floor it below 2000rpm, I get nada.

I attempted to screw with the alda a bit, as this was suggested by some to remedy low power situations.

Is there a chance that I could have broken the ALDA?
Is there a way to test the alda? can I remove it, and see if i get a normal smoky takeoff then?

And one more thing, I can a tiny whine from the turbo (i assume its the turbo) when going about 25-30mph in the S gear (3rd i think) this is roughly 2100rpm, is this a normal thing? should it spool sooner/later?
Its hardly even audible, but there is a hood pad on this car, so that could be muffling it a bit.

Any suggestions/input?

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion