Cannotget fan speed to pick up when going to max air.

DESCRIPTION The dual radiator fans are mounted to the back side of the radiator . The radiator fan consist of the fan blade, electric motor and a support shroud which are all serviced as an assembly.
OPERATION COOLANT TEMPERATURE
A/C PRESSURE TRANSAXLE OIL TEMPERATURE Fan Operation Speeds: Initial Max Initial Max Initial Max Fan On: 104°C (220°F) 110°C (230°F) Fan Speed Duty-Cycles (Ramps-up) from 30% to 99% 1,724 Kpa (250 psi) 2,068 Kpa (300 psi) Fan Speed Duty-Cycles (Ramps-up) from 30% to 99% 96°C (204°F) 111°C (232°F) Fan Speed Duty Cycles (Ramps-up) from 30% to 99% Fan Off: 101°C (214°F) Fan Speed Duty-Cycles (Ramps-down) from 99% to 30% 1,710 Kpa (248 psi) Fan Speed Duty-Cycles (Ramps-down) from 99% to 30% 89°C (192°F) Fan Speed Duty Cycles (Ramps-down) from 99% to 30%

Sounds like the engine is toast.

indicates that the fan is not drawing air through the radiator at idle or low road speeds
If viscous fan hub --replace it
if electric fans check
coolant temp sensor
2 fuses , relay . fans . ECM

Change the relay, situated in a black plastic box up in front of the battery. Costs about 7 pounds / 11 dollars USD on ebay and takes 30 seconds to do. Until you get it fixed, protect the engine when temp get over, say, 90 degrees celcius, by opening up your side dash vents, turn the in-car fan on max and the temp up to max. The hot air will go directly out the windows and you will see the temp gauge drop back to about 80 degrees. I did this for a year until I figured out the relay needed replacing.

Remove your blower and you'll probably find it has a bad bearing,or the fan wheel is defective or loose. They are usually not that difficult to replace. don-ohio

I had the same problem with mine, it did not pick up speed on the hills and max at 35mph on steep climbs. It ended up being a diaphram on the back of the carborator that does not come in the carb rebuild kit so you will have to find a carborator specialist in your area and see if they carry it. That diaphram controls the secondaries for the extra horse power needed for picking up speed and going up hills.

when it's on 'auto', the fan adjusts according to the temp in the car and the temp setting you have it set at. try setting the auto temp control down to 65, then hit the "-" one more time to send it to "LO" - the fan should automatically jump up to max.

Check the blower motor resistor pack is not faulty.
The resistor pack (for speed control) is usually located in the blower fan ducting in the air flow .

I replaced the power control module. The module is located, electrically speaking, between the A/C head unit and the blower. Physically it is behind/under the glove compartment in the air ducting for cooling. The GM parts counter charged me ~$140.

Hey Summers,, Are you running the A/C with the temperature set at max heat?? If yes. STOP... the A/C is for COLD air..As far as the fan speeds not working....you may have a fan switch that is going bad..(my vehicle is doing this!)..