The house had its roof replaced about 5 years ago, it was holed by some storm, It has apex vents and also has a silver radiant barrier on the ply (not all around though, the insulation is mighty thick, in some places its more than 2 ft of it.

Im calculating about installing ductless A/C units to control the temperature, but Im noticing for the time being that the little fans I installed on the walls are helping out

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

thats a good one.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Before I considered messing with the system I'd clean of the t-stat and play with it to see if it actually controls the dampers.
Set to 90? Try tweaking it to 65 and see what happens. Some one set it up at some point...
Look upstairs and all around for an 'unused' dimmer dial that might be a damper control.
Go into the attic, get the info-make, model on the airtrol thing and look it up on the 'net.

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95 E300D working out the kinks
77 300D, 227k, station car
83 300CD 370k, gone away
89 190E 2.6- 335k, no more
79 VW FI Bus- 145k miles, summer driver
59 VW Beetle ragtop- 175k miles
12 VW Jetta- 160k miles

I would suspect that two dampers indicate two zone controls. Trace the wiring if possible from the currently closed damper to its source. That said being as far north as we are in eastern Canada my air conditioning experience is more than somewhat limited.

Even this far north we have issues with our attic ventilation. I am experiencing shorter shingle lifespan for some time.

Yes we have ridge vents and soffit ventilation that is not restricted. I am thinking of putting in a temperature controlled exhaust fan system in the attics. Other than that I will have to switch to steel roofing. My suspicion is that the current shingles have been cheapened beyond belief.

armed with a bottle of gatorade, my DMM and strong shoes, I was doing some testing in the attic.

comes out that I have this zone controller

honeywell trol a temp mm2
https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-1361.pdf

its wired up just as the diagram shows.

now the fiddly parts

the zone1 is controlled by the upstairs thermostat (but zone 1 has 0 volts on the damper control - 2 wire motors)

the zone 2 which is wired to the downstairs stat actually gets signal of 24V to its damper motor - but the thermostat is now not even switching the the A/C on.

the way its supposed to work is that either thermostat can call for A/C or heat function but not both. The system will open the damper the called zone and run the unit.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Again with almost no experience. See if the twenty four volts is present at the upstairs thermostat. The thermostat may be in the ground leg but suspect not. Checking the one downstairs should indicate how they are doing it. Plus when you turn it on that it is really switching the 24 volts to the load or loads. Could be as simple as a bad thermostat.

.If the thermostat checks out then on to the relay or relays it controls. Since zone one is functional there is not much in the circuit for the second zone. At least the control circuits are not solid state. Since you have a meter you should be able to get through it.

You have one good circuit so compare it to the other. Hook it up to the other box, see if it works.

I switched the wires of the dampers between zones and now the other damper works - seems like the zone controller is gone a bit duff. Its got 4 relays in there, two trace to zones, and the other two trace to the furnace.

Furnace is switching on and off = thats good
one zone is good
the other zone control relay is bad (no activity)

I figured out that one stat with the 6 wires is the main stat and if I physically move the switch to off - the other stat (slave) wont work. The other stat is pretty old too - Im going to change it anyway.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)