Our new to us '77 280E has developed a coolant leak at a devices on the passenger side of the engine bay. The top of the box has eleventy billion vac hoses going into/out of it.

Is it an auxiliary water pump?

That's the climate control servo. Your best bet is an Unwired Tools upgrade.

There is an aux water pump in that area. In the picture below, the water pump is on the left and the servo is on the right.

http://unwiredtools.com/accii.asp

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Is there any way/ill effect to bypassing the heater circuit then? It is already a/c weather down here in south Texas. The climate control system seems to work perfectly, except for the leaking from the servo.

The AC thermostat drives the evaporator temp at a constant 38*. The servo adds heat to bring the cabin temperature to whatever temp you select. Without the servo in play, you will have sub-40* air blowing out of the vents, continuously. I know it gets hot in Texas but...

That's the only disadvantage I can see.

You would need to hard wire the compressor to stay on.

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MB-less

Are you saying if coolant flow is removed the heater circuit, the compressor will not turn on?