2007 Buick Luzern fan motor for the heater cuts on and off

Question edited for clarity, 'year make model' should be first as it is the most important piece of information and allows the site scipts to suggest the category.
Question moved from Misc to make model category.

The climate control is controlled from the Body Control Module. You will need an auto electrician with a pro grade scan tool computer to check the data network for the heater controls.

https://www.google.com/search?q=2007+Buick+Lucerne+CX+3.8.+Blower+motor+not+coming+on

https://www.google.com/search?q=auto+electrician+near+me

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Could be ! could also be the blower motor is bad or blower motor control module .
Does you buick have manual or automatic climate control ? There is a fuse box under the rear seat ,that is where fuse is for blower motor .HVAC BLWR fuse 40 amp. Chevy Trailblazer EXT Blower Motor Won Turn Off

http://www.partsgeek.com/gbproducts/MC/2682-07038968.html?utm_source=google&utm_medium=ff&utm_content=MC&utm_campaign=PartsGeek+Google+Base&utm_term=2002-2007+Buick+Rendezvous+Blower+Motor+Resistor+Standard+Motor+Products+RU-50+02-07+Buick+Blower+Motor+Resistor+2005+2003&fp=pp&gbm=a&gclid=CLzvqdvmyrQCFQHwzAodKGkANw

A cheap cooling sensor might not start the fan. Make sure the one you or your mechanic bought is a quality product.

check for power at the plug that attaches to the fan motor. if it has power then replace the fan. if not then trace the wire back to the relay to find the short.

replace thermostat

On most vehicles, there is a thermostatic switch located on the bottom tank of the radiator that controls the electric fan. When AC is turned on, this switch is bypassed so its failure is 'cured.' These switches aren't terribly expensive nor difficult to replace but ensure you don't lose coolant on the ground while replacing the switch since the stuff is tasty and toxic to animals.
If you like to be able to research and or repair minor problems like this, you might consider buying the Haynes manual for your car. This will also let you approximately access what a repair might cost for labor if you can see the degree of difficulty yourself.
Haynes Buick manual
These are available at auto parts stores often cheaper than the online price. We have on for (and IN) each vehicle we own since they can be lifesavers now and then.

your losing ground too it ,run a new ground from the battery too the base of the fan motor!!!!!!!

Ros.....The heater motor is located under the dash on the right hand side (passanger side). You will have to remove the close out panel to access. The resistor you are looking for will be to the lower left of the fan motor at about the 7:00 position. Illustration is below.
let me know.
regards,

Fan will be under dash on passengers side , Removing glove box might be needed, Gm also uses a blower resister ro control fan speeds. First check your fuse and then check and make sure your getting 12 volts to the terminal at the blower, You could have a blown fuse, a bad switch, or a bad resister , if your getting voltage to blower motor then most likely it will be the motor. These are not to difficult to change. I hope this helps, please be aware I can only guess at what the problem is from my past experience.