A/C fan is either on high or off when in auto mode

your fan blower switch is bad. check with your buick dealership auto parts for price of a fan blower switch and location. they can print out a location for you. don't buy the switch until you check the old one with a volt/ohm meter, unless the switch cost is reasonable.

easy we love these,
year, car, and model, and actual accurate , symptoms.
i must assume it runs on high , a key factor.
my guess is 4 = max. or high.
most cars high is bypass mode, (direct fan drive)
so tells you that the speed reduction part is DOA. in part or more...
on most cars this is called the fan resistor block.
ill look up that in my USA FSM and see. now.

ok with or without climate control options,
i roll dice and land on none.
this car does have the fan resistor block 3 speeds (resistors) and dirct drive for 4 total speeds.
your resistor block is bad.

if your car has the V6 or advanced climate control option
all the above is Bull.
the CC options uses advance fan modulation to run the fans
PWM its called. and usaully never fails
the CC system has self test mode, its in the FSM , ill not attempt
to do that, pages, long.....
there you go,
Btw all this was at alldata.com and the free fsm.

http://hondatech.info/downloads/Auto/Manuals/Accord/


my guess is, it's a non CC car.

blower motor resistor to replace, on the blower motor where the wires connect

check the resitor under the dashboard near fan blower motor

Check the fuse panel box for blow fuse or the fan may just need to be replaced they tend to go out after some time.

sounds like the sensor is becoming questionable or a hi resistance ground in this part of the blower sensor circuit

you need to repace the bolwer motor resister,can't tell you where it is because all cars are different but am almost positive that this is what needs to be repaced.

Check fuse ,switch or blower motor.

I believe you are going to need a new control unit as it has the blower resistor built into it. It may have a seperate resistor though, so ask your local dealer or parts store for a blower motor resistor.

HI Had same Problem. Found the door sensors had droped and not in correct possiation. the differance light stays out and functions properly. if the door sensors not on check degree the light stays on.