cooling fans high speed/low speed

A high speed fan mode would only be on if the engine is overheating which it does sounds like it is. Is there something wrong you is it just something you noticed?

Cheers, Ken

Thanks for reply Ken...I am a Honda Master Technician, this 05 Buick Rendezous V6 is a freind who said my daughters car is overheating, can you install this thermostat and coolant he thought would fix her problem. The complaint/issue their having is the Temp Gauge on the dash is reading 1/4 or so...but less than half way nice and steady....then at times it goes quickly up to 3/4!...then back to 1/4 again. so...
after checking a few things I dont think the car is overheating at all, with a scanner reading engine coolant temp...i see that when this episode occurs temp is around 220...also when the low fans come on...which i now learned is normal on this car...and again after fans are running for like 45 seconds the gauge goes from 3/4 right back to 1/4!
So now im thinking there is a problem with the switch that sends the signal/temp reading to the gauge!!
or the gauge or that circuit.......another reason is a GM Tech said that on this model at normal temp..the gauge should be at 1/2 right in the middle!! maybe resistance no good in that switch!!!
what do you think?

Yep. it sounds like the coolant temperature sender is going out. There is just one for the gauge and the computer. Here is a guide that will help you see what you are in for when doing the job.

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Here is what it will be like on your car with the location (below)

Please let us know what happens.

Cheers, Ken