I have an older Bryant Funance 80 system with A/C. The other day, the furnace would not ignite electronically. It was deemed by the serviceman to install a new board. So the new board was installed and the ignitor works but the furnace is short cycling.. meaning the burner comes on for just a few seconds and then shuts off and then cycles again.

Then the serviceman says I probably need a new thermostat. The thermostat I had was a Honeywell that was non-programmable and has separate controls for Heating and A/C plus Auto and On for the fan. The serviceman said I could put a jumper wire on the Rh and W contacts and the heat would work but never shutoff until I unhooked the jumper.

I went out and bought another Honeywell thermostat to match so that I could easlity replace the existing one. Prior to me installing the new one, I would like to know a few things. On the Bryant circuit board, the following 5 wires are used and attached to the thermostat termainal blocks which has the G, C, W, why, and are terminals.

My first question is why do I have to jump between the Rh/Rc and W contacts on the thermostat to makue the funace burner to continuously run?
The second question is why is there a jumper between the G and why terminals on the circuit board, instead of just having the G go to G on the thermostat and why going to why on the thermostat?

Went and checked the wiring, there are 6 wires on the circuit board thermostat terminal block... red on G, white on Y, red on Y, white on C, white on W, and red on R. I did find that one white wire had snapped off so I trimmed and reattached it. Of those 6, only 4 go to the honeywell thermostat and of them, red is on Rh with jumper to Rc, white is on W, white is on Y, red is on G. And the other 2 go to the outdoor A/C unit. With that configuration, the unit fires the burners for a few second and then is extingushed and then recycles and does the same thing.

I installed the new thermostat and everyhting is working fine... thanks