My 300TD is stuck on defrost setting. No matter what I do I can't seem to get the front climate controls to not be on defrost. help

the engine shuts off & the brakes work fine so its not a vacuum issue. seems like its a climate controller button not "popping out" when changing modes...

I'm going on memory so I may or may not be right. I seem to remember that defrost is the default mode when the pushbutton unit quits working.

__________________
Jim

I’m pretty sure defrost is the default mode when the CCU looses vacuum supply. Green with yellow stripe IIRC

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

it is the default by my indie, but i checked vacuum and it's there...

Take the CCU out of the dash, and twist it and squeeze it while the engine is running. CCU issues are often bad connections on the circuit board and twice i have diagnosed a bad CCU by having it work correctly while holding it and twisting it gently.

__________________
1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660

wheres the ccu on a w123?
thx!

It is the pushbutton unit.

__________________
Jim

thx

Turns out I have a spare unit in my garage. I'll swap it tomorrow.

There you go.

__________________
Jim

Right. ^^^

Replace that row of selector buttons. I had to do that on my '83 300SD - problem solved... It was a pricey item, as I recall at the MB Dealer.

__________________
'06 E320 CDI
'17 Corvette Stingray Vert

So my spare 123 830 12 85 unit operates only when twisting ...
However the 107 830 26 85 which was rebuilt and is the exact same size + takes the saw fittings functions perfect.
Why shouldn't I use the 107 unit?

Thx srj!

If anyone needs a PCU rebuild check out ProgRama.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer