No Heat

[PDYoung]

It got into the 40's today so i tried to switch on my heat for the first time .All i get is cold air coming out of the vents.Did i knock something off under the hood this summer when i put the supercharger and headers on? .Where under the hood should i look ? This is where i suspect the problem is.I would take it to the dealer for warranty work,but i'm affraid once they get a look at what i've done,their going to tell me my warranty is void.

[00Silverado4x4]

What are your engine temps? Is it possible your thermostat is stuck open?

[txab]

Make sure the cooling system is completely full. Low fluid levels have caused no heat conditions as has been reported by other members