I could not find a post addressing this specific problem, if there is please point me in the right direction.

I am replacing two old thermostats with digital new ones.

One side of the house is working although when the compressor comes on the display gets so dim that programming is impossible.

The other side kept resetting itself. After I swapped the two new thermostats it stopped resetting and instead it made a clicking noise when the compressor comes on. That same clicking noise I can hear at the compressor fuse outside when the compressor is running. I figured that is not a good thing and put the old thermostat back.

The old thermostats did not have the blue common wire attached but the wire was there so I connected it to the new thermostats.
As long as the compressors do not run everything looks fine. Programming of the totaline thermostats works, lights come on.

I followed the manufacturers instructions and bridged C to W with the supplied resistor. That makes the clicking (switching) slower but not by much.

So I wonder could it be that the transformers are not supplying enough power, do I need to replace them, or are there any other suggestions. Thanks.

Since you didn`t tell us the make and model numbers of the tstats,, it will be impossible to look them up to help you much. (digital new ones),is just no help..

Did you check to make sure the blue wire you hooked to the tstat is hook up on the other end in the furnace/airhandler,, it sounds like you may have a loose wire somewhere that's not making real good contact.. Usualy the blue common wire does away with the need for a battery

The new thermostats are totaline - totaltouch P286-1500.
I will have to check for the connection at the furnace

Wiring

http://www.ntsupply.com/files/products/totaltouchwiring.pdf

There is a phone number here for you to call with problems but I can tell you that thermostat has to be powered up by the 24 volt transformer because if operated battery only the batter lasts about 20 hours and then it is dead.


http://www.ntsupply.com/files/products/TT_1500.pdf

This thermostat has to be setup for specific installs also and the outdoor kit.