Once you’ve determined that the controller and valve are working properly, you need to take a closer look at the wiring to determine where the problem may lie. In this case you need to first locate track the wire path with your wire & valve locator, then you can zero in on the problem using a ground fault locator.
A ground fault locator when used properly and in conjunction with a wire and valve locator can save you hours of aimless searching on the job site. This is a specialty service and should be charged as such. Your hourly rate will be higher but in the long run this will save your customer money and instill confidence in your abilities as an irrigation technician.