I have an older Carrier WeatherMaker 1 rooftop unit. I replaced the blower wheel for the vent but the wheel get red hot. I don't really think this is supposed to happen. The blower wheel is a Fasco 1-6052, CW rotation and blows really well. I had replaced the ignition module before this and then the rusted blower wheel fell apart. The motor makes a slight noise but nothing terrible. The unit is approx. 17-20 years old. Any suggestions would be appreciated.

The vent temperatures are way to hot. Usually that means the unit is overfired. Start by checking the gas pressure at the valve and go from there.

If the wheel is rubbing against the casing(causing your noise) this can cause the wheel to get hot.

Is it actually RED hot, or just to hot to touch.

Hvac most likely gave you your answer. Let us know what you find.

The motor could also be in the process of failing. When the bearings give out the unit will over amp and get very hot.

Your other question posted back to me was how to check the gas pressure. You need a tool that has adapters to tag to gas valve or the gas train.

Something like this

TestProducts.com | National Safety Products, Inc. | 877-412-3600 | <- (http://www.testproducts.com/product_info.php?products_id=564)

The required manifold pressure should be listed on the furnace plate or tag.