OTB,

Try switching the non-working terminal connection with a working terminal connection in the electronic timer. Let us know what happens. Aloha

No change. The #5 and #6 terminals are just as good as the #4. Both will start the #4 solenoid, but the #4 will not cause the water to flow through the #5 or #6 solenoids. I unscrewed the solenoid and flushed it and the relief valve. Reconnected everything and still it only works if the relief valve is opened.

OTB,

Did you manually turn the solenoid valve off only enough to stop the water and not over-tighten? I assume that the #5 and #6 valve were the ones not working from the controller. You then connected #5 and #6 wires to a previously working terminal #4 and the valve still didn't work. The cheapest thing at this point is to replace the solenoids(not expensive) on the non-working valves. Otherwise do continuity test on #5 and #6 and see if you have a short in the lines to those valve. Check the electrical connections of the solenoids to the white common wire. Let me know if you are familiar doing this or I can take you step by step. Aloha

Bad diaphragm. Turn off the water supply and take one of the valves apart. I am assuming they are all the same valve. Go to a sprinkler supply house nearby or buy them off the internet. Get diaphragms for all the valves. They tend to age the same. The others will be failing shortly.

Good luck,
Tom

OP here: I got valve#6 to work by simply backing off the solenoid by no more than a 15 degree turn. As for valve#5, I decided to check the diaphragm, as suggested, since nothing else worked. I opened the whole thing; the diaphragm looked as good as new: dark color, flexible, no signed of cracks or holes. I blew through all the holes at the solenoid and relief valve and the center of the diaphragm, I reassembled it all --- and it worked! As I've always said, there's nothing like a good blow job!

OTB,

Glad to hear it. Thanks for sharing. Aloha

There are 3 possible reasons that backing off the coil helped.

1. The coil's plunger has a rubber piece on the bottom that has become deformed. Sometimes the rubber swells out and closes the gap between the plunger and the hole it covers when the coil is not engaged. Take a very sharp razor and trim the swelled out part. Be sure to trim it very level or it may fail but this time in the open position.

2. The diaphragm is bad. When the diaphragm goes bad it begins to allow more (or in some cases less) water to pass by it than the coil can handle. Small micro holes in the diaphragm, plugged holes in the diaphragm or the metering hole in the diaphragm are reasons this may happen. When I said before your diaphragms were bad this was a broad statement. Taking apart one valve and checking the diaphragm may have fixed your problem by removing sediment or dirt that was causing too little water to bleed past the diaphragm.

3. This one is rare and hard to fix but in rare cases (happened to me the other day for the first time in 2+years) the hole the plunger covers has moved up. This hole (in most valves) is a plastic or stainless insert that the plunger closes off. For some reason this insert moves up just a tiny bit. Now when the plunger gets pulled up by the coil there isn't enough clearance between the hole and plunger and the valve will not open.

My guess is your diaphragm(s) will fail on you again sometime soon, one day to 2 years, and will need to be replaced. The job is very simple just be careful to not let any dirt get in the valve or screw holes.

Good luck,
Tom