116 Climate Control - Aux. Waterpump

Last week my '80 300SD's climate control seemed to have died - just cool air, no fan no heat. I've owned the car since new and have learned a bit about this climate control system, so I tried the DEF (override) mode -
a brief spurt of fan and a bit of heat and it died for good.
Fuse #2 and fuse #9 were blown. I also found some coolant seepage on the auxiliary water pump. I unplugged the electric pump's power line and replaced both fuses. The climate control resumed its regular operation - heat, fan etc. - all works fine.
Today I used a jumper lead to test the auxiliary pump - only a very brief hum then silence. Apparently coolant seeped into its motor and shorted it.
The heater works well without the auxiliary water pump so if you encounter this problem simply unplug the pump's power lead and leave the pump in place or remove it from the car and substitute a piece of pipe.
This climate control is plenty complicated so a bit of simplification was the solution.
Another example of: "Why make it simple if we can make it complicated."
Tom Lambach '80 300SD
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Good tip, Tom. I am wondering why they even put an auxillary pump, unless there is a heater in the back seat.
--Geoff '84 300D
"T.G. Lambach" wrote:

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Supposed to pump hot water at low engine speed. Mine was dead, never noticed it.

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Fred Emmerich
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Same thing here. I replaced mine and haven't noticed any real difference. The only benefit may be if you start the car cold and then let it idle while waiting for someone ( a woman usually), then you may get heat faster. If you drive off, the regular water pump provides sufficient water flow by itself.
fred snipped-for-privacy@comcast.net wrote in message said:

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