Question
My Sprinkler has 4 zones with 4-5 heads in each. Till last fall every zone worked well and I winterized the system in fall. Now in spring, when I dewinterized it, zones 2,3,4 work with good 50psi pressure however when I switch to zone 1, the pressue drops to 0 and no heads pop up or even make a sound. What could have gone wrong in the system?

Answer
Sounds like you have a leak or that something is wrong with the wire for that zone. Turn the zone on and check around the area for leaks. Sometimes they are sneaky so you might have to wait a little bit. If no leaks are found then test and make sure you have power to your valve. If you had a service winterize your system then see if they shut the flow control off on that zone. If the valve has a flow control.