Heating/AC Unit in Emergency Mode

[Daniel Feuer <dfeuer@xxxxxxxxxxxxxxxxxxxxx>]

Trying to find possible root problems for my 1988 735i's heating problem.

The heating is in "emergency mode", meaning that only heat is blowing from the
defog vents under the windshield.  Now it being warmer weather, makes it for a
hot interior.  The heat is on when the fan level is in the off position and
does not increase as you move through the dial, except for the high level,
which it blows at high.

What are the possible causes for the system for going into emergency mode?  I
assume that there are a few answers.

Thanks!

Daniel

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