The ball that rotates, to adjust the temp (heat and/or ac), does not produce an immediate result. For example, if I turn the heat down, it takes 3 or 4 minutes for the change to take place. The heater will keep blowing hot until, a while later, the heat is reduced. The same is true with the ac. Any change made with the temp control will not start for 5 minutes. Any ideas?

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Jacob Wissler Jr., Houston, Texas, 1984 300 SD

Check that the aspirator blower is working. It's the little fan attached to the main blower housing that sucks air through the cabin temp sensor by the rear view mirror. Check also the temperature-resistance values of the cabin temp sensor. The values are in the archives.

If it's only slow from hot to cold then check the seals in the monovalve cartridge.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD