From experience, most likely culprit, besides splices, would be the screens and their related plugs.
Back in the day, if you were lucky they used AMP 2 position pull aparts, but the pins/sockets were tin and not plated. If you're unlucky, they used a non-standard plug. Your bugs and contacts are most likely not sealed units, strictly mechanically actuated, so replacing those with contemporary sealed reeds will also help loop resistance.
I have also seen the 2 conductor zip cord start to rot out from the inside out over the years.
The big variable is how the house was wired originally....you may not be able to split zones, so now it's determining if you can split and refeed rooms or zones to break up the continous loop.
There's little secrets on how to get a high resistance zone to function without falsing, but it's a last resort.
Back in the day, if you were lucky they used AMP 2 position pull aparts, but the pins/sockets were tin and not plated. If you're unlucky, they used a non-standard plug. Your bugs and contacts are most likely not sealed units, strictly mechanically actuated, so replacing those with contemporary sealed reeds will also help loop resistance.
I have also seen the 2 conductor zip cord start to rot out from the inside out over the years.
The big variable is how the house was wired originally....you may not be able to split zones, so now it's determining if you can split and refeed rooms or zones to break up the continous loop.
There's little secrets on how to get a high resistance zone to function without falsing, but it's a last resort.
