This is kind of a long story - Believe it or not this is the Cliff note version.
I purchased a house last year on Long Island (South Nassau County). Originally it had an oil furnace (2 heat zones) and window air conditioner units. Before I moved in I hired an HVAC contractor to install two central AC units (one for each zone).
As part of that installation, the contractor installed two basic Honeywell thermostats in the same location as the old ones. The new thermostats now controlled both the heat and the air conditioning.
The thermostats worked fine, but within a few weeks we realized that the thermostat in the upstairs hallway was not in a good location. The house is a pretty open layout so it was picking up the heat from downstairs and we were having a difficult time regulating the temperature in the bedrooms. I figured the easiest way to resolve the issue would be to purchase a wireless thermostat. That way I wouldn't have to move any wiring around. I would keep the receiving unit wired in the same location as the old upstairs thermostat and I could place the sending unit in my bedroom. Specifically I chose the Venstar T1100RF unit.
I hired the same HVAC contractor who did my CAC to install the Venstar unit. Immediately he noticed two problems. First, I have a two transformer system, but the Venstar unit only had an "R" input. There were no separate RH and RC inputs. Second, the Venstar required a 24 volt common wire which we didn't have in the wall. He resolved the RH/RC problem by putting both of them into the single R input (and told me not to run the AC and the heat at the same time). For the 24 volt common - he found an extra wire in the wall that went down to the basement, and connected it to the transformer on my oil furnace in the basement to make it into a common.
The Venstar system worked nicely until September of this year. That's when my old oil furnace died. I contacted the same HVAC contractor and hired him and a plumber friend to do a gas conversion. They completed that job, installing a high efficiency Alpine gas furnace.
Immediately after the job was completed, I started getting repetitive (and loud) clicking noises coming from the Argo relay box next to the newly installed gas furnace. It would almost sound like a heartbeat. Click-click... click-click.. etc. The HVAC contractor came back and immediately agreed that this wasn't right. Interestingly, when the AC wires (Y,RC,and G) were disconnected the clicking would stop. This seemed strange because these wires had nothing to do with the heat - so why was it affecting the furnace's relay box. Ultimately the contractor decided that the thermostat was probably fried. He agreed to install a new one which I would purchase. In the meantime, he left me with a temporary thermostat to control just the heat.
I purchased another Venstar thermostat but the HVAC guy didn't seem in such a big rush at that point to come back. After a month of him not getting back to me, or promising to come on a certain day and not showing up, I told him his services would no longer be needed.
I contacted my electrician to install the new venstar thermostat. However, he (wisely) told me he wouldn't install the Venstar since it isn't meant for two transformers. I decided at long last to try and do things the right way. I purchased a Pro1aq t955W wireless touchscreen thermostat, which has separate RH and RC inputs and is thus usable in a two transformer system.
Today the electrician came to install the new thermostat and lo and behold, the second it starts calling for heat, the same clicking noise starts. So now it seems that the old venstar thermostat wasn't broken. But what is? The electrician attempted to bypass the thermostat and turn on the AC - and it wouldn't power up. So he theorized that perhaps the relay was blown on the CAC. Later on it occurred to me that the AC might not power up because the temperature outside is in the 30's farenheit. Another theory the electrician had - he called me later on after he discussed it with a friend - is that perhaps the 24 volt common that is now coming out of the Argo relay box is the problem. He suggested that perhaps I need a separate 24 volt transformer for the common.
At this point I have put in close to $1,000 in parts and labor for this thermostat issue and all I have are a couple of theories. I am not a DIY person - I want to pay someone to get it done right. But I don't even know where to start as far as finding someone - and what to even tell such a person when I do find him. I've called a couple of contractors who have heard the first half of my story and they cut me off to tell me they aren't interested - and seriously, how could I blame them?
I would appreciate any input that you guys might have because I'm way over my head here. If anyone has any good ideas I'm all ears because I seriously don't even know what to try and do at this point.