[QUOTE=Sprinkus]Two things I would check at this point are the gauge of wiring that was run to the valves and the water pressure to the system.
Undersized wiring to the valves can cause this type of problem as well as excessive pressure at the valves.
16 gauge wire should be the minimum wire size for a small residential irrigation system, if the contractor used 18 gauge or smaller wire then there may be enough of a voltage drop when the solenoid is operating to cause damage to the solenoid.
Excessive water pressure at the valve will cause the solenoid to have to work harder to open, the increased amperage required to operate the solenoid can also cause damage to the solenoid.[/QUOTE
Although the voltage drop may not be the only problem with the Weathermatic valves, I certainly agree with the concept of the gauge wire being too small for the length used. I would only add that the gauge must be decreased (larger wire) as the length is increased between the controller and the valve solenoid. The key is to measure the voltage across the solenoid, as close to the solenoid as possible, while energized. Then measure the voltage at the output of the controller while energizing that same solenoid. The difference between the voltage at the controller and the voltage at the solenoid is the "voltage drop" or loss due to the length and gauge of wire. A 5% voltage drop MAY be tolerable (check with valve mfgr), but the less drop, the more powerful the solenoid action will be. To be told to use any particular gauge wire with no consideration of length is ridiculous, but is a common mistake made by many installers, system designers and, sorry to say, even some EE's. EXAMPLE: 18 gauge copper wire, at 20 degrees C, has a resistance of 6.385 ohms per 1000 feet. That means that in a distance of 500 feet (2 wires = 1000 ft) from controller to valve, using a 20 ohm solenoid that your voltage drop will be, simplistically, [(6.385 ohns/20ohms)(24 volts)] = 7.662 volts, or about 32% (7.662volts/24volts)..... way toooo much! I realize that a 500 foot run is likely not too common, but just use the same math for any distance you may have using 18 gauge wire. If that 32% is not reduced to less than the mfgr's specification for adequate operating voltage AT THE SOLENOID (not at the controller), then you will have to increase the size (decrease the gauge) of the wire or some how increase the voltage at the controller for only the high resistance (long) wire runs. 16 gauge copper wire is 4.016 ohms/ft and 20 gauge is 10.15 ohms/ft, both at 20 degrees C. Hope this helps.