what does the little water pump do. i've seen it called secondary or aux water pump but is it essential to engine cooling? balance in the cooling system? or just for heating the interior when called on. mine hasn't worked probably for years and years and while the temp guage never shows above the absolute max it does seem to fluctuate alot. when at idle the heat inside the cabin kinda goes away and gauge risesand when driving, heat comes back and gauge goes down.

 

In addition to heating the passenger cabin the auxillary pump can be used in a pinch to cool the engine. If your main water pump goes out and the auxillary works, you can turn the cabin heat on high and still drive short distances as the auxillary pump will circulate coolant from the engine to the heater block disipating some heat.
Unfortunately that is the predicament I'm currently in, any suggestions on why a water pump would go out after a coolant change or how to make it pump again would be greatly appreciated.

 

I just took my 81 out after 3 years in storage and am still trying to get a grasp on why this aux pump will not work. This pump runs and pumps when "hotwired" to the battery, but not when it is connected to it's harness. I have checked all fuses. I have called for max heat with fan on high. This proly hasn't worked for some time and i don't normally use the heat as the car is rarely if ever driven in winters. I am sussing out all this cars problems such as tires alignment engine mounts and an odometer that didn't work this year. But this still eludes my attempts to correct it.
Has anyone had this problem and what did the fix turn out to be.

 

The Aux Water Pump has no Fuse.
If the Aux Water Pump shorts out to ground internally it can burn up part of the Board in the Climate Control Unit and has been rumored to occasionally cause Fires.

Over on another Forum some people have added a 3 amp add on Fuse in the circuit.

According to the Manual your Heater Blower is not supposed to come on until you Coolant Temp heats up to a certain amount. I am guessing the the Aux Water Pump is not going to start running until the temp is up also.

With or without the Aux Pump when the Coolant is hot you can get heat for you Defroster and eventually the Heater.
My Axu Pump is Dead and I have never removed it to see why so due to the Fire hazzard issue I un-plugged it.