Thermostat "Rc" vs. "R" or "Both"

[dave981]

My house is setup with an Air Conditioner and a Heater that share the same fan "R" cable.

I recently acquired from my mother-in-law an Honeywell "Chronotherm III", which I had planned on using to replace my simple thermostat.

When I hooked it up with the Red cable connected to the "R" connector, when I set the thermostat to "COOL" it flashed "-AC", which I read on other forums to mean no power to the Fan... So i took apart the thermostat and connected the Red cable to the "Rc" screw. That fixed it so my Air Conditioner then worked, but my Heat no longer worked...

SO, I decided to attempt to connect the Red cable to both the "Rc" and the "R" at the same time. Now setting the thermostat to either "Heat" or to "Cool" seem to work - Is there a danger in doing this?

Thanks for any help / insights anyone can offer.

Dave

[Hube]

A "Jumper" wire between R and RC is what it needed, no problem...Hube