Help With Short in Orbit 6-Station System
I have an Orbit 57976 that has been working fine for years but recently the fuse blew. I replaced it, and it worked a week or so, then blew again. In the manual it says this indicates a short. (Dad has passed so I am trying to fix things!)
Following the advice of a friend I replaced the fuse then put the unit on Manual to start the automatic program while standing there, then pressed the NEXT button to cycle through each station, looking for the one that would not come on. He said that's where the short will be.
Station 5 did not come on, so I went to that station (backyard) and noticed this is where the unit is grounded to a pipe that runs into the ground. (Ground wire runs back through garage wall to unit.) The top of the pipe looked rusty so I took off the grounds (2 valves grounded there as well) and sanded the top of the pipe, and redid all the connections to the pipe, though I did not replace the ground wire that runs to the unit... just stripped it down a bit to get new wiring.
Put in a new fuse and started the manual watering again, this time forwarding through to Station 5, which now came on and watered, then it rotated to station 6 and watered. Great!
Only the next time the auto-program came on, the fuse blew again. So I replaced the solenoid in Station 5, assuming it was that and not the ground wiring.
New fuse and on we go. Cycled manually through all 6 stations quickly and each came on.
However the next time the auto-program came on, it blew again. (Auto program comes on at 4am so I don't know which station it blew on.)
So today I put in a new fuse and stood there, and started the program manually and instead of hitting the NEXT button to go through quickly I wanted it to go through the entire program normally. So it started watering Station 1 and after about 3 min the fuse blew!
I went to Station 1 (front yard) and unwound/uncapped all the connections to all 4 Stations there (starting with Station 1) and they are all pristine and done very well. (A plumber did these about 8 months ago when a valve needed replacing.)
Since the system worked a few minutes before shorting out, am I correct in suspecting this is a wire that is heating up, rather than a bad connection?
Or could it be that the solenoid of Station 1 is bad? But would it work for 3 min if that was the case?
Just seems like a ground issue, still, though I am no electrician! I am thinking maybe I need to replace the ground wire that runs from the pipe to the unit?
Thanks so much for any help anyone can offer! I also have a voltmeter but don't really know how to use it beyond setting it for AC (it has auto-dial in)... I don't know what is a normal reading for a sprinkler system or solenoid, or where to put its probes. Sorry for my ignorance.