[V8] Cooling Fan Question

[Ted Haug]

Hello V8 Listers,

I took on the task of swapping out my thermostat today.  Noticed that she had been running cooler, and took quite some time to come up to operating temperature.  The thermostat was in all likelihood the original from the factory, as I have owned the car since 1995 and this was the first time it had been changed during my ownership.  Well, it appears as though changing it out wasn't a bad idea, and it was not really all that bad of a job.  I did notice, however, that the electric fan cycles on and off constantly....literally it is spinning the the entire time the car is running...but you can hear it cycle on and off.  It is running at a low speed, but factor that it is constantly turning, along with the viscous fan....and it is going to be quite a feat to get some heat into the cabin.  Especially when the outside temps are hovering near freezing.  

So, the question then becomes....what is cycling the fan on and off at that low speed, even though the engine for the most part is cold?  I recall that the V8 has a rather complicated system for controlling the fan, which includes several sensors along with the instrument cluster.  I was just hoping someone had run into this before, and can steer me in the right direction.

Many thanks to all in advance,

Ted H.

82 4000 4E
86 Coupe GT
90 V8 quattro