Ford: Climate control 1999 f250 diesel, chiltons manual, vacuum pump

Question
I am having trouble diagnosing the problem I am having with the climate control, it will not select anything different now it is stuck on deforst.  The vacuum pump on the fender well runs continously now and if disconnect the main line from the pump and plug it the pumps stops like it would if operating normally, but if I remove the line out of the vacuum reservior on the wheel well and plug the vent out of the reservior the pump will not shut down, like it can not product enough vacuum in the reservior to cause the pump to shut down.  I can not figure out how to get the reservior off the wheel well to inspect it for any damage or leaks.

Do you have any suggestion on the reservior removal or better way to diagnose the problem?

Thanks,
Dan

Answer
Some of these reserviors, are not to be removed. Then some are and can be replaced. But I just cant thing of what year they can be replaced. I would look into a chiltons manual for the procedure, for removal, and replacement. Otherwise, I would have your Chev Dealer check it out for you. Sorry couldnt help you more...