Hi Folks:
I rebuilt my auxiliary water pump( aka recirculating pump) using the procedure given in following thread. However, I did not change the carbon brushes. For me it was too complex. Its a very nice procedure by '79 Super Turtle.


auxiliary water pump rebuild W116 and others.

It was a little hastle to get the motor cover off but I did it.
Then I did a hail Mary- I got the electric motor cleaner spray from NAPA and cleaned the motor especially the carbon brush and the carbon brush contact area.
Cleaned the magnet in the housing as well with the spray.
Let the whole thing dry nicely.
But that as far as I could go with my skills, (carbon brushes looked too complex to mess with).
Put the motor back in the reverse order.
Did not attach the pump yet.
Then the testing part, using a 12 V DC supply from AC to DC adapter (you will find many of these in your house), and WOW it worked.
I let it run for 3-4 minutes then reversed the polarity and let it run for 2-3 minutes.
All looks fine.
Then reassembled the pump and tested it in the car.
Works like a charm.
I don't know for how long but for now I am OK.
I plan to put 1 Amp in-line fuse so as to protect the other circuits in case the pump starts drawing up too much current, this way I protect the pump and the other components like ACC board.
My advice, If you can get a used one for 25-30 bucks get it and replace don't go through the hassle unless you have time on your hand, and also be aware that you might not be as lucky as I was just by cleaning it.
I am attaching the image file for the pump component.

Thanks hope this helps
MVK

Attached Thumbnails

 

__________________
One penny saved is three penny earned.

1985 300D Turbo 179,000miles

Do a search of the threads related to this, particularly the pushbutton ACC unit and somewhere within those many threads there is a discussion that mentions the amperage that the control unit is rated for.
If I recall correctly it was mentioned that the controlling circuit and component is maximum rated at 1.2 Amps.
So in order to protect the electronics you would need a fuse rated to blow below that rate!
A 1 Amp slow blow in a waterproof in line holder placed into the power feed circuit from the would seem to fit the bill nicely.
Good Luck!

Thanks billybob.
I think I will go with 1 amp fuse for now.
My question is can you please tell me which of the 2 wire I would cut to put an in line fuse.
I want to put it just before where the Auxiliary water pump plugs in.
I am confused on which wire will I cut.
The pump operated on 2 wires, one must be the ground and I don't think you put a fuse on ground wire.
Am I right?
If I am right than can you tell me how to find which one is ground wire and which is not.
Thanks.
MVK

__________________
One penny saved is three penny earned.

1985 300D Turbo 179,000miles

According to the FSM for the 107 chassis for '78-'79, the ground wire for the aux heater pump is the brown wire. This means that the red wire(from plug to pump) or the black (<yeah, I know it goes against conventions, but thats per FSM>, from the plug to the switch) is the positive wire.

__________________
". . .back before accountants designed cars"

-Current Stable-
'78 MB 450SL-C 107.024.12.020783 #3840 <Kayleen>
'85 FORD F250 6.9L Diesel <Allison>
'98 Lexus ES300 <Rachel>
Long Gone...
'74 Chevy G10...........................'99 GMC Yukon 4X4
'83 Chevy Suburban 6.2 diesel .....'99 SAAB 9-5
'90 Mitsubishi Eclipse GS............. '01 Chevy Tahoe
'98 Nissan Altima .......................'02 MB ML320
'88 Chevy Suburban V2500 4X4 6.2 diesel

This DIY is good for many MB Chassis.