i would trust MR.TIEGER'S advice more than any other plumber licensed or not.
"We have tried everything from wrapping all exposed openings on cord to putting a plastic bag over the timer and insulating it all with a towel." ...
if i was troubleshooting this then the first thing i would do would be to turn the supplies off,(hopefully you have shutoffs under the sink)disconn...
is that a fire sprinkler service line? also is that second valve in the closed position? just curious.
if they need to change the meter then they don't have to shut if off at the street.or if you need to change that second valve same thing.it's just ...
no you can fish wires through walls with a minimal amount of damage if you know what you're doing and you have the correct tools.i've done quite a ...
i would suspect the flush valve needs to be replace.or try just the seal if it's one of those mansfield 210 or similar.
all it needs is seats and springs.go to that web site that i posted and you can see how it comes apart.
find out if the raised or lowered the water pressure coinciding with your problem. for starters.post back.
i would go with a three conductor to save wear and tear on the fan pull chain switch,since you're starting from scratch.
anytime i was ever called for that i was always able to fix it by removing the cartridge and then turning on the water to flush it out. once there...