I have a customer with a DLAS075 furnace. It takes way too long for it to heat up enough to close the fan switch. I am leaning toward the booster assembly but I am not sure. My thought is that the burner is not getting enough air to make the fire hot enough. The gas pressure is correct and nothing is plugged. Ever had this problem?

It's possible that the fan switch itself is defective. Are you sure it's not coming up to temp?

I checked the temperature on the furnace right where the fan switch is. The switch is a 105-20 switch. After the burner on for 20 minutes the temp was 95 degrees.

What does the flame look like through the viewing port? Take the gas valve off and look at the orifice, it may be plugged with a spiders nest, it's actually pretty common.

I finally found out the problem as you know. The orifice on the burner had a spider web in it. Thanks for the help.

When the furnace gets ready to turn on right before it makes a loud noise then comes on also the fan sounds louder