94 E320 Climate Control Issues

[DslBnz]

Specimen is 1994 E320.

Symptoms:

1. Compressor does not engage
2. Blower Motor works fine
3. Blows extremely hot air when warm

What has been done:

1. Determined there is no power to the compressor at any time
2. Found corrosion underneath battery tray
3. Sprayed WD40 over corroded areas and cleaned
4. Replaced KD/Klima relay unit

Things of potential relevant interest to note:

After I cleaned up the area of the corrosion, and reseated the tray and battery, I started the car and engaged the ACC. I turned on the single-level compressor button (middle) and everything began to function AS IT SHOULD. In other words, ice cold AC, and a perfect compressor function.

Subsequent attempts yielded nothing but the original scenario. What does this sound like, guys?