Temperature control problems on my 2000 silverado pickup.?

I am having problems with my temperature control on my 2000 silverado pickup. Whenever I have it on cold it works just fine, but whenever I switch it to heat, and then try to go back to the cold, it just stays at heat. I have replaced the control module and that did not do the trick. Any advise would be appreciated on how to troubleshoot this or where I could find some detaild wiring schematics online...thanksTemperature control problems on my 2000 silverado pickup.?
There should be a vacuum control valve in line on one of the heater hoses under the hood. It sounds like this is malfunctioning.Temperature control problems on my 2000 silverado pickup.?
There is a box that has a electric motor in it that moves the blend door to make it go from hot to cold that is bad.I had to replace mine as it had the same problem. Its on the bottom of the dash on the passengers side of the hump. You must remove the panel on the bottom of the dash to replace it. Have someone show a picture of the dash at the dealer and then you can see it . And the is a procedure to follow when the new one is installed. Don't just bolt it up or it will be out of whack. also you can replace the cabin air filter while you have that panel off while you are there........UJN
yes aske your dealer shop tech if he can give you a picture of the wiring drawing from the shop manual and ask if he can explain it to you. Very complex dont forget to give a tip he will like it and may help you with other problems. be one on one bases