Why would someone disconnect power to auxiliary water pump during summer?
 

In one of the posts I read while trying to figure out how to install an auxuiliary water pump, someone mentioned that he disconnects the power to the pump during the summer months. Anyone know the rationale for this? Granted, there's no need for heat at low rpm, but why go to the effort? Just curious.

because you do not need to circulate heat through the cabin.

perhaps they have a bad coolant valve

CCUs have been reported to be damaged by aux pumps that fail.

That's right...I knew that....in the earlier designs there was no protection for the CCU. Thanks.

Disconnecting the electricity won't prevent the aux pump from failing, though, because failure is almost always caused by coolant leaking into the electrical side and corroding it into a solid mass. The unprotected CCU in the W123 models then fries its pc board traces unless you have installed a fuse. The later W124 CCU has protection built in. A disconnected aux pump may actually be more likely to fail than one that gets used year-round.

If one is really serious about extending the life of an aux pump, one would have to remove it from the engine and insert a tube to connect the two pieces of rubber hose. The aux pump could then be disassembled, cleaned, lubricated, reassembled, and stored away in a cool, dry location, then re-installed when it gets cold. Considering how much time it would take to do that every year, it would be a lot less expensive to just use the pump until it fails and then get a new one. With the correct mix of MB coolant and distilled water, the aux pump should last many years.

If one lives in a very mild climate, the recommendation would be to permanently remove the aux pump.

Jeremy

I believe one of our members had the interior of his car burned. The Aux Water Pump with no Fues in the circuit was the suspect.

It has happened to many. I installed fuses on our three SD's.....and its not plugged in on my bro's 300D, but it still has mega heat at all rpms, interestingly enough. The W201 and W124 don't have fuses as they don't need them....and both of them have smooth running aux pumps anyways.