Aspirator Fan Blower Motor
 

Yes, I know I've posted this over on the TECH pages...Some of the Petrol
Burners are concerned that even "Looking" at a Diesel page may put the
"HooDoo" on their Fine German Automobile.(They have enough ELECTRICAL
FUN as it is...No Further Help Needed in those Quarters)

Interesting idea. The W124 CCU is supposedly designed to shut down automatically if the aux water pump freezes and draws too much current but I don't know if that also applies to the little aspirator fan. Can you post a complete image of that page of the schematics?

It shows that they are all powered by the same fuse, but doesn't show that they are all grounded by the same output from the CCU. If they were, you'd close the monovalve, run the aux pump, and run the aspirator blower all together.

Besides, I have spare CCUs, I've already bought two cars with bad ones/bad aux-pumps.

To fuse or not?
 

It looks to me like the aspirator blower is connected directly between fuse 7 and ground so that it runs whenever the ignition is "ON," which agrees with my experience. It still might be worth adding an in-line fuse of an amp or so . . . no, wait.

[waiting . . . ]

I've just completed bench testing a spare aspirator blower. At 13 Volts it draws a little less than 0.1 Amp; when stalled (by putting a finger in the vanes) the current increases to 0.25 Amp. Thus, a fuse of about 0.15 to 0.2 Amp would allow the fan to run but would blow if the motor froze or jammed.

Given the small amount of current drawn and the fact that the aspirator is not powered through the ACC unit, I don't think a fuse is necessary. Still, it's food for thought: are there other things that we should be fusing in our cars?

Jeremy