@Paul_in_FL Thanks much Paul. I am not in that residence but will try it when I get there. Hans

@jj5724 What I did was to connect the old router with a network cable to one of the ethernet ports of the TPlink. Then I chose it as router on the thermostat but with no other device.

@jj5724 I got it to work again! I simply connected the old router (Apple Airport. Extreme) as additional router.

@jj5724 Thank you very much. So, I would be looking at $1200 for the S30 plus the work to put it in of up to $450 and then the WiFi would not even be in the S30 but the furnace/AC unit. I am holding...

@jj5724 Let me know if the new thermostat is a S30 and if it works with the A8. My guarantee has expired and it would be very costly to replace the thermostat. If it works with the router I might do...

@jj5724 Thank you, that is very helpful. I also have the older model with the white frame and will check if it really is still under warranty. It is more than seven years old.