[W126 Coupe] Looking for a short in the A/C circuit.

[Dan Stratton]

The A/C Heater circuit fuse keeps blowing on my '87 560 SEC, I've  
unplugged the aux water pump and the A/C compressor, but still no  
luck. Fuse is fine, if I just turn the key on, but the minute I start  
it up - it blows. Where is the mono valve? I thought it should be  
right near the aux pump (next to the battery) , but I don't see it.

Dan