a little more info---if it helps any i took the time to blow out the 4th line last night and all of the heads popped with air coming from all of them .
when i first turned on the sprinkler the first three zones worked fine but there was nothing at all from the 4th zone.After checking the wiring which was fine i removed the celenoid and put it back on and one head in the yard began to work but that is all.the other 3 heads in the yard have not gone on at all .Could it be the valve or the celinoid can a celinoid go partially bad, or there is something elese i should be looking for? . thanks tony
