I do not think the lightning is the cause, I think it was caused by the
overheating of the transformer itself, this happened because the
transformer is rate too low for your load. Check the voltage before
applying the load, and then apply the load to see its voltage drop. If
the drop 40% or more then, you'll need to buy a bigger transformer, do
not buy the exact model.



Cam

The transformer was an original factory replacement part. Do I check the
voltage drop on the load side or the line side? The control box is
outside and in sun in the morning when the sprinklers are on, could the
sun cause the overheating.
Mike

The Sun could add more heat to it while in operation. You would check the
secondary (output side 24Vac)

It should not drop so much, (10% is typical 21volts) 40% = 14.4 Volts or
lower is terrible. I've seen these transformers before at Home Depot,
they look small to me for continuous operation. I have it too for door
bell, door bell is low load, that's why I don't have problem with it.
Yours must have a big and continuous load, that's why you're having a
problem statically (because in a coil, high voltage is self-generated
through energy delay release, this may be why it jumps between the wire
after overheating.



Cam


I narrowed the problem to one zone using your suggestion. The voltage
dropped on one zone from around 24v to 15. All of the others had only a 1
volt drop. Next I need to narrow it down to the zone wiring or the box. I
am going to switch two zones and see what happens. If that doesn't work I
will switch the solenoid. I just hope it isn't the wire to the solenoid.

Mike