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#1
11-01-2009, 11:49 PM
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Where does the CCU get power from?
This is a 1980 W116, 280SE. US version.
I know the CCU (and aux water pump) is supposed to get power when the ignition is off- so it can return to the "home" position after you shut off the car. I'm not getting any power to it right now for some reason. Does it have a fuse? I don't see anything for the CCU in the fusebox. Where does this thing get its power from? Where can you check for it? jk 
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#2
11-02-2009, 12:37 AM
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Most everything in a car runs through the fuse panel. On your W116 it will be under the hood in a box on the drivers side. Check/replace all the fuses with the proper amperage ceramic type and see if it solves the issue.
Oh, and the climate control does not get power when the ignition is off. There is no "home position", it is vacuum controlled. I assume you are talking about the evil climate control servo. Do a search on this forum about "evil servo" and you'll learn a lot about it.
__________________
-diesel is not just a fuel, its a way of life-  '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k)
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#3
11-18-2009, 01:49 AM
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still digging
After looking at this again, I learned a bit more, but I still have no heat. The servo does indeed return to the "park" position electrically after the ignition is shut off. The power comes from an inline fuse (in the fuse box but not in the rows). The fuse in the holder is a weird one, doesn't look like any other fuse I've seen before- a tiny glass tube with metal ends and green rings around it.
Anyways, As soon as I re-seated this fuse, I heard the servo whirring itself to the park position. So that's good. I also notice the aux water pump is moving coolant now with the engine running. Also a step in the right direction. I tested the ACC servo unit as well. The valve opens when I apply 12 volts straight to pins 3 and 5 (simulates fully open DEFrost setting), then it closes again when I reverse the polarity. The measured resistance at pins 1 and 2 is exactly as it should be for any given setting. So the servo seems fine. But switching on the ignition and selecting DEF at the console, I would expect the connector side to deliver 12 volts as well across pins 3 and 5. I only get 8 volts. Does this mean the amplifier is shot? Or does this suggest a bad connection at the selector switch? I feel like I'm very close on this one. Anybody have a clue? jk
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#4
11-18-2009, 02:19 AM
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A halogen bulbs also uses a tungsten filament, but it is encased inside a much smaller quartz envelope. Because the envelope is so close to the filament, it would melt if it were made from glass. The gas inside the envelope is also different -- it consists of a gas from the halogen group.
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#6
11-21-2009, 09:57 PM
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it was the amplifier
So the amplifier was probably delivering the proper voltage to a couple pins in there, but was failing in some other crucial way. It's surprising because it's a refurbished unit, less than a year old. I swapped a spare amplifier and everything suddenly started working perfectly.
Thanks for everyone's help. When the whole system is working properly, it's really very nice. Next . . . vacuum leaks, broken tach, sloppy steering box, new tires, taillight gaskets, new seat padding and springs . . . jk
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#7
11-21-2009, 10:15 PM
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The amp may have been providing the proper voltage, just not enough current...
__________________
A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608 Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL. 
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