I bought a new Honeywell RTH3100C thermostat. The old thermostat had a white wire looped around both E and W2. What do I need to do?

Read your manual on page 16.

http://customer.honeywell.com/techlit/pdf/PackedLit/69-2340ES.pdf

Thanks for info. Been trying to find a wire this late at night to jump from E to AUX. Wire too thick in junk pile at the houses they are constructing in my neighborhood. Walmart does not have solid core copper any gauge in electrical department. Automotive only rated for 25 volts AC. I bought a $1.97 circuit tester took it apart but wire is multi strand aluminum. Is that good enough?

Guess not AC would not start. Notice an old thermostat there is a copper bar from W1 to Y. Do I have to add jump wire between AUX and Y, also?

You should only have to add what the instructions say. Is the is a 2 stage heat pump? Gas furnace A/C? Or what?

Two stage heat pump

Hi HVAC1000
Found this problem similar to mine with your answer but am still trying to decipher exactly what you meant.

https://www.askmehelpdesk.com/heating-air-conditioning/wiring-honeywell-thermostat-t8411r-rth3100c-179004.html